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Fabrication and characterization of nickel silicide nanowire electrodes by solid-state diffusion controlled growth for supercapacitor / Mohammad Mukhlis Ramly
No full textThe growth of nickel silicide nanowires (Ni3Si2 NWs) using solid-phase diffusion controlled growth were studied in this work. The Ni3Si2 NWs were grown on Ni foil and Ni foam substrates coated with Ni film using a home-built chemical vapor deposition (CVD) system. The studies started with the effect of silane (SiH4) flow-rate and substrate temperature on the growth, structure, and electrochemical properties of the NWs. Ni3Si2 NWs were grown on Ni foil by optimizing SiH4 flow-rate (1 to 5 sccm) and substrate temperature (350 to 500°C). These variations produced a different type of Ni3Si2 NWs morphologies such as dendritic, ultra-thin, and root-tips. The ultra-thin NWs have an average diameter and length of 16 ± 3 nm and 6.5 ± 0.5 ?m respectively, with the aspect ratio of 406. Next, the optimization of the growth parameters to obtain high quality of Ni3Si2 NWs was carried out by varying Ni film thickness in between 90 ± 5 and 220 ± 5 nm. These NWs exhibited morphology of straight NWs with diameter and length between 16 to 23 nm and 2.9 to 3.9 ?m, respectively. Based on these three optimized parameters, the high-density Ni3Si2 NWs demonstrated the highest specific capacity value with a maximum value of 330.5 C/g at current density 1 A/g. In the last part of this thesis work, the optimum parameters from the three variations were selected to growth Ni3Si2 NW with high density and straight nanowire morphology, and high electrochemical performances, to fabricate a hybrid supercapacitor electrode. The supercapacitor performance of Ni3Si2 NW-based electrode on Ni foil and foam was evaluated and compared. This highly dense packed thin, straight, and long morphologies NWs on Ni foam have an average length and diameter of 12.5 ± 0.3 ?m and 13 ± 2 nm respectively, with a high aspect ratio of 961 owing to their extremely large surface area (5.184 x 1011 NWs/cm2). The fabricated Ni3Si2 NWs/activated carbon-based asymmetric supercapacitor exhibited a maximum specific capacity of 578.3 C/g, an energy and power density of 62.24 Wh/kg at 387.5 W/kg respectively, together with a good cyclic stability with 76 % capacity retention after 3000 cycles. The correlations of the electrochemical performances with their morphology, compositions, and structural properties of Ni3Si2 NWs are summarized at the end of the thesis
Operational structural damage identification using de-noised modal feature in machine learning / Chen Shilei
No full textStructural damage can severely affect the safety and functionality of the structure and
lead to economic loss. Vibration-based structural damage detection has raised continuous
interest over the decades, as a non-destructive way to provide warnings and predict certain
faults at early stages. Compared with conventional modal parameters such as the natural
frequency and mode shape, the upstream modal data, namely the frequency response
function (FRF), can be a better alternative, because it is rich in modal information and
can be easily obtained. However, the FRF is usually measured through experimental
modal analysis (EMA) when the test object is in shut-down mode, which is not practical
for real-time application in the working environment. This limitation can be overcome by
a novel technique named impact-synchronous modal analysis (ISMA) performed under
the operational condition. Machine learning is also a focus in this work, which was
employed to process and classify FRF data in terms of damage. By integrating ISMA,
both supervised and unsupervised machine learning algorithms were investigated to
develop real-time damage identification schemes. Specifically, the back-propagation (BP)
network was employed in the supervised learning method, and the FRF changes in a
selected frequency interval at several measurement points were used as the input of the
network. The unsupervised learning method was developed by combining principal
component analysis (PCA), waveform chain code (WCC) analysis and hierarchical
cluster analysis. WCC analysis was carried out on the PCA-reduced FRF to extract
damage-sensitive PCA-WCC features. The unsupervised hierarchical cluster analysis was
then conducted on these features. The proposed schemes were tested on a rectangular
Perspex plate. The results show that the similarity between the FRF obtained by ISMA
and EMA exceeds 0.993, proving that the de-noising method of ISMA provides static
comparable FRF data during the in-service condition. For the supervised learning method,
the trained BP network can successfully identify the scenarios of high and moderate
damage with an overall accuracy of 100% when all five measurement points are used.
With the input features optimized by mode shape assessment, 100% accuracy can also be
achieved with only two measurement points. For the unsupervised learning method, the
hierarchical cluster analysis can correctly cluster the samples in terms of their damage
states. In terms of damage severity and location identification, the proposed scheme is
sensitive to detect damage severity with damage index as low as 0.05. In addition, the
combination of PCA-reduced FRF and mode shapes shows a positive correlation between
the magnitude of the resonant peak and the displacement of the impact point in identifying
the damage location of the plate. In conclusion, the supervised learning method using
FRF change is convenient and effective in identifying the damage state of the plate, and
can be optimized through mode shape assessment. Meanwhile, the unsupervised learning
method using PCA-WCC features is good at detecting unknown damage, and is sensitive
to low-severity damage. With the help of PCA-reduced FRF, it is also feasible to estimate
the severity and locate the damage of the test plate
Perceived importance and understanding of collection development policy amongst academic librarians in Nigeria / Buhari Yakubu
No full textDespite the importance of collection development policy (CDP) in developing library collection, little has been written about the perception and knowledge of those who are responsible for formulating, maintaining, and updating this policy, especially in Nigeria where collection development challenges seem to be rampant. The objective of this study was to assess the perceived importance and understanding of collection development policy among academic librarians in Nigeria. The study employed a quantitative methodology using a survey research design. A survey questionnaire developed based on the IFLA (2001) guideline for the collection development policy was used to collect the data for this study. One hundred and thirty-six (I36) academic librarians were recruited from three selected academic libraries in the Northwestern zone of Nigeria using a stratified sampling method. Data were analyzed using descriptive and correlational analysis. The findings revealed that academic librarians had a high perceived importance and understanding level of CDP. The findings also revealed that educational level had a statistically significant correlation with the perceived importance (p = .000) and understanding of CDP (p = .009). However, the working experience had no statistically significant correlation with the perceived importance (p = .100) and understanding of CDP (p = .307). This study has contributed to the management of academic libraries by providing useful and reliable information on the perceived importance and understanding level of CDP among academic librarians in Nigeria. The study recommends that various educational programs should be developed to provide a better perception and understanding of CDP among library professionals in Nigeria
Synthesis and biological studies of nickel(II) complexes of thiosemicarbazones / S Savina Savir
No full textEleven Schiff base ligands have been prepared from the condensation of N3-substituted thiosemicarbazide with fluorene-2-carboxaldehyde (L1-L3), 2,3,4- trihydroxybenzaldehyde (L4-L7) and 2,5-dihydroxybenzaldehyde (L8-L11). Their corresponding nickel complexes have been synthesized with two general formulations of [Ni(L)2] (1-3) (where L= L1-L3) and [Ni(L)PPh3] (4-11) (where L= L4-L11). The compounds were characterised by FT-IR, 1H NMR, 13C NMR, and single crystal X-ray diffraction. The results suggested that the thiosemicarbazone ligands behaved as bidentate (L1-L3) and tridentate (L4-L11) ligands which were coordinated to the Ni(II) ion via their N,S atoms displaying a square planar geometry (1-3) and their O,N,S atoms displaying a distorted square planar geometry (4-11), respectively. Among the compounds tested, ligands L3 and L5, complexes 1 and 4 showed higher cytotoxicity against HCT 116 human colorectal carcinoma cell line than cisplatin. It is noteworthy that ligands L6, L7 and L8 showed higher cytotoxic activity against PC-3 human prostate cancer cell line than cisplatin. In addition, complexes 2, 3, 5 and 6 exhibited moderate in vitro antimalarial activity. In general, the antimalarial activity of the compound increases as the size of the substituent increases. However, this may not always be the case as anomalies in trend may occur. Our findings revealed that complex 6 displayed the highest antimalarial activity probably due to the more hydrophobic substituent attached at the N(3) position
Development of artificial neural network models for predicting lipid profile using smartMF electrical parameters / Ahmad Zulkhairi Zulkefli
No full textThis research project aims in the development of artificial neural network (ANN) to classify lipid profile parameters; total cholesterol (TC), triglycerides (TG), high density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) by utilizing a non-invasive bioelectrical impedance analysis (BIA) device (SmartMF). Data were obtained from volunteer patients requiring lipid profile testing at the primary care department of University Malaya Medical Centre (UMMC).
The data were divided into two categories for each lipid profile parameters, normal and abnormal. Statistical analysis including T-Test and logistic regression analysis for the bioelectrical parameters were employed to understand the data and determine suitable predictors to be used for the development of the ANN. Results of the statistical analysis indicates capacitance, resistance and reactance as significant predictor for TC level. Impedance at 50, 100 and 200 kHz, resistance and reactance as significant predictors for TG level. Impedance at 5, 50, 100 and 200 kHz as significant predictors for HDL-C level. No significant predictors were determined for LDL-C level, thus ANN model for the parameter cannot be developed.
ANN employing the multi-layered feed forward neural network technique was developed for the TC, TG and HDL-C parameters utilizing the scaled conjugate gradient (SCG), Levenberg Marquardt (LM) and Resilient (RB) backpropagation algorithm. The best model was then selected based on the testing performance.
For TC, the SCG model with a testing accuracy of 73.3%, sensitivity of 63.6% and specificity of 78.9% was selected. For TG, the LM algorithm with a testing accuracy of 76.7%, sensitivity of 28.6% and specificity of 91.3% was selected. For HDL-C, the SCG algorithm with a testing accuracy of 76.7%, sensitivity of 95.5% and specificity of 25.0% was selected as best performing models to indicate the relationship of the bioelectrical parameters and the lipid profile parameters
Identification of ergonomics risk factor and work-related psychosocial using DOSH risk assessment on backpack leaf blower workers / Amy Zuria Abdul Ajid
No full textCleaning industry is one of the main sectors that supports national economic growth and cleanliness is an essential element in healthy living. Ergonomic, health and safety
awareness is important to make sure the industry excel. There are many type of cleaning service involve in this industry but this study only focus on cleaning workers who uses backpack leaf blower machine. The usage of backpack leaf blower is very popular in cleaning industry because it is time-saving, efficient and mobile. Objective of this study is to identify worker’s body part with the experience of ache, pain and discomfort among backpack leaf blower workers. This study also was conducted to assess physical risk factor and psychosocial work factor that causes back pain and body discomfort to backpack leaf blower workers. Ten respondents who works as cleaner in one of a local
university was analysed using Ergonomic Risk Assessment (ERA) which was adapted from Guidelines on Ergonomic Risk Assessment at Workplace 2017 by DOSH Malaysia to determine ergonomic risk level of the employees. From the analysis conducted and calculation of Total discomfort score, body parts which are at risk for injury and discomfort on female workers are wrist (right hand) with scores of 20.98%, lower back (18.17%), legs (13%) and shoulders (12.19%). Male workers on the other hand shows that, the body parts with high risk of injury and discomfort is on the shoulders (20.81%) followed by neck (17.59%), right wrist with 17.24% and lower back (16.29%). Factors contribute to risk of injury and discomforts are awkward posture (head bending forward, twisted torso and wrists in flexion position), repetitive motion (uses of hands, fingers, wrists and shoulders intensively), vibration (on hands and all over body) and load carrying activities (working with loads on the back for a long walking distance). From psychosocial aspect lack management control in work schedule rotation, heavy workload, long working hours and management failure are main caused. Employers are responsible to create awareness about ergonomic besides creating procedures and safe work practices which can lessen the pain and discomfort to the workers
Study of Schottky and Poole-Frenkel conduction mechanism in Fe304-gamma-Fe2O3/SiO2/n-type Si system / Adrian Chung Ning Hann
No full textThe advances of metal oxide semiconductor technology (MOS) have led to smaller devices being made where sizes of the devices keep getting smaller and compact. Hence, all the components of metal oxide semiconductor sizes are to be reduced without affecting the overall efficiency of the metal oxide semiconductor. However, there is a problem in the silicon dioxide component of MOS as the sizes of the silicon oxide (SiO2) reduces, there is a possibility a current leakage to occur due to carrier direct tunneling effect passing through SiO2 which reduce the efficiency of the MOS. Therefore, a higher dielectric constant material where Fe3O4-γ-Fe2O3/SiO2/n-type (magnetite-maghemite nanoparticles with silicon dioxide) silicon system is chosen to tackle the problem. This material is to be study with the experiment data of the material in order to investigate the Schottky and Poole-Frenkel emission as well as to identify the dynamic dielectric constants of both emissions and barrier height of the Schottky emission of the material. The results show that the linear fitting of Schottky and Poole Frenkel emissions are well fitted with the standard model equations which suggested that both emissions are present during the experiment. Subsequently, the calculation and observation of the plotted graphs showed that the highest dynamic dielectric constant, kr of Schottky emission is 6.6927 at 200°C while the highest dynamic dielectric constant kr of Poole-Frenkel emission is 8.6505 at 150°C and the highest barrier height, ΦB of Schottky emission is 1.6242 at 200°C. In conclusion, the overall results show that the combination of Schottky and Poole-Frenkel conduction mechanisms are responsible for the soft breakdown, EB of Fe3O4-γ-Fe2O3/SiO2/n-type silicon system in a high electric field and high-temperature environment
Power system analysis and optimization for BioApps RoMicP® foot prosthesis / Mohammad Bilal Goolfee
No full textA critical component of a motor-powered prosthesis is the power system that generates
the required torque at the joint by converting chemical energy stored in batteries into
electrical energy and finally mechanical torque. Prior studies focus mainly on the control
system of prostheses and barely cover the power component. In order to achieve high
power efficiency in the RoMicP® prosthesis, this study investigates the required battery
specifications through calculations, as well as the power consumption of the LMG5200
inverter system and the feasibility of a multilevel inverter configuration using the
simulation model and software (available online) from the manufacturer, Texas
Instrument. The results showed that to fulfil the design requirement of weighing below
2.5kg, the battery size required is 10Ah at 24V and can power the prosthesis for 5k steps
per day. Moreover, using the LMG5200, an efficiency of 99.72% was achieved through
PWM switching with harmonic distortion of 2.15% for a three-phase output. Furthermore,
the proposed multi-level inverter design achieved an efficiency of 59.46% with harmonic
distortion of 0.82% and could therefore not be recommended for use in this case, although
it demonstrated that a multi-level system could generate cleaner output. In summary, this
project successfully investigated the battery requirements, power consumption and
efficiency of the simulated system, as well as the feasibility of a multi-level inverter
topology. Future studies should focus on investigating other multi-level topologies, and
increasing the number of levels, as well as different advanced switching techniques such
as Space Vector Modulation
Investigations on wheelchair seating pressure relief system for pressure ulcer prevention among paraplegics / Norhani Md Nadzri
No full textIndividuals with paraplegia spend their time in a wheelchair for life. Adapting to prolonged wheelchair seating for almost all activities of daily living is challenging. The loss of abilities to sense any pain or excessive seating pressure cause them to remain seated on the wheelchair without any pressure relief activities. This situation leads to secondary complications including pressure ulcers which further degrades the individual�s health. A wheelchair seating pressure relief training system (WSETs) was developed to overcome this. Optimal placement of the force sensitive resistors (FSR) as seating pressure sensors on the cushion was determined, and their responses were investigated with 5 people with paraplegia. Two different FSR orientations, A and B, were compared. Each paraplegic sat in a resting position and then performed pressure relief activities (PRA) which included whole body push-up, left and right lean and forward lean, before returning to resting position. With more forward positioned FSRs, Orientation B showed higher sensitivity, implying better capture of the high-risk areas of pressure ulcer development. The FSR sensor readings were significantly different among pressure relief activities in all subjects (p<0.05), indicating the validity of FSR measures for the intended application. In conclusion, the WSETs system was proven suitable as a training tool for new paraplegics to habituate themselves in performing PRA
The pharmacokinetic of silver diamine fluoride in healthy children with dental caries / Lim Siau Peng
No full textSilver diamine fluoride (SDF) is a medication used topically on carious tooth surfaces
to arrest caries progression in both child and adult populations. This study aimed to
determine the pharmacokinetic of SDF in 15 children who received SDF treatment. Urine
samples were collected at baseline, and at first and second 24 hours after SDF treatment
to determine silver and fluoride levels. Hair samples were collected at baseline, and at
days 7, 14, 30, 60, 75, and 90 after SDF to assess silver levels. The median and
interquartile range of urinary fluoride at baseline, first and second 24 hours after SDF
were 498.33 (381) µg/24-hour, 574.92 (318.87) µg/24-hour, and 474.35 (324.21) µg/24-
hour, respectively. The pairwise comparison results indicated that urinary fluoride levels
at the first 24 hours after SDF treatment were significantly higher than those at the
baseline. However, the higher urinary fluoride levels are not sufficient to cause fluorosis
as SDF is not for daily application. The range of urinary silver levels at baseline, and the
first and second 24 hours after SDF were <1 µg/24-hour, 1 – 2 µg/24-hour and <1 µg/24-
hour, respectively. Although urinary silver levels were higher in the first 24 hours
following SDF, statistical analysis was not possible due to their extremely low levels. The
range of hair silver levels after SDF treatment (< 0.2-0.69 µg/g) were found to fluctuate
around the baseline level (<0.2-1.7 µg/g). Based on these study results, the use of SDF is
safe in children.
Keywords: Silver diamine fluoride, caries teeth, children, pharmacokinetic, safet