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- PublicationValidation of plasma probe hardware platform for in-situ measurement and monitoring of atmospheric parameters using sounding rocket(2024-04-01)This thesis presents the validation of a plasma probe hardware platform for insitu measurement, accompanied by a real-time communication system. The objective is to create an integrated system that combines a plasma probe hardware platform with a reliable and efficient real-time communication infrastructure. The hardware platform incorporates multiple sensors, including temperature, magnetic, accelerometer, camera, pressure, and GPS, to enhance the understanding of the relationship between in-situ plasma probe measurements and environmental parameters. The real-time communication system ensures seamless data transmission between the platform and the ground station operator during the data collection process, providing valuable realtime access to the collected data. This feature also serves as a redundancy solution in the event of recovery failure, ensuring that data can still be transmitted and monitored even if the platform cannot be recovered. Through this integrated approach, researchers can monitor, analyse, and make informed decisions based on the collected data in real-time, even in challenging recovery scenarios. The validation of the plasma probe hardware platform, coupled with the real-time communication system, advances our capability to study plasma phenomena, offering significant implications for space exploration, atmospheric research, and related scientific endeavours.
- PublicationSynthesis of molecularly imprinted polymer-ordered mesoporous silica adsorbent for batch and fixed-bed column adsorption of chloramphenicol(2024-09-01)This study describes a novel synthesis of a surface-imprinted polymer-ordered mesoporous silica adsorbent for highly selective chloramphenicol (CAP) adsorption using activator regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). Initially, ordered mesoporous silica was synthesized by the sol-gel method and functionalized to prepare a silica-ATRP initiator (SiO2@Br) for polymer grafting. CAP was used as the template molecule for imprinting via precipitation polymerization. The effects of varying polymerization reaction parameters, such as template to functional monomer molar ratio (1:2 – 1:10), template to cross-linker molar ratio (1:4 – 1:20), solvent types (acetonitrile and toluene) and their mixtures (0 – 100%), catalyst to ligand ratio (1:2 – 1:10), catalyst to reducing agent ratio (1:2 – 1:10), reaction temperature (313 – 353 K), and reaction time (6 – 30 h) on imprinting factor (IF) values and adsorption capacities (Qt) were studied. The physical and chemical properties of the resulting adsorbent were analyzed using FTIR, TGA, EDX, SEM, HRTEM, and nitrogen sorption techniques. The SiO2@Br had a specific surface area of 638.31 m².g-1 and a total pore volume of 0.4152 cm³.g-1. Post-polymerization, the specific surface area and pore volume of the adsorbent (SiO2@MIPs-CAPcr) decreased to 11.91 m².g-1 and 0.019 cm³.g-1, indicating successful grafting. Adsorption performance was investigated through batch and fixed-bed column studies. Batch experiments investigated the effects of initial solute concentration (10 – 50 mg.L-1), adsorbent dosage (5 – 25 mg), temperature (293 – 313 K), and initial pH (3 – 11) on CAP adsorption. The adsorption equilibrium data for SiO2@MIPs-CAPcr were well fitted by the Sips models, with a maximum adsorption capacity (Qs) of 19.68 mg.g-1. The adsorption kinetic followed pseudo second-order behaviour. Thermodynamic analysis indicated an exothermic process with entropy change due to reduced molecule movement. Selectivity studies involved antibiotics ciprofloxacin (CIP) and thiamphenicol (TAP) as model adsorbates. Fixed-bed column experiments tested initial concentrations (10 – 50 mg.L-1), volumetric inlet flow rates (0.1 – 0.5 mL.min-1), and bed heights (0.5 – 1.0 cm). The Thomas model best described the fixed-bed column adsorption behaviour. The SiO2@MIPs-CAPcr adsorbent demonstrated remarkable selectivity for CAP and excellent adsorption capabilities in both batch and fixed-bed operations.
- PublicationFuzzy-based vector control system for permanent magnet synchronous motor(2024-12-01)Permanent Magnet Synchronous Motor (PMSM) is highly regarded for its efficiency, power density, and dynamic performance, making it integral in industrial automation and electric vehicles. However, traditional PI controllers often struggle with parameter variations, nonlinear characteristics, and load disturbances, affecting steady-state and dynamic performance. This thesis addresses these challenges by proposing a Fuzzy PI control strategy that combines Field-Oriented Control (FOC) with Fuzzy logic, enabling adaptive adjustments of PI parameters for enhanced stability, robustness, and responsiveness. MATLAB/Simulink simulations show that the Fuzzy PI controller achieves faster steady-state response, reduces steady-state error, and minimizes overshoot across various speeds, including 500 and 1200 r/min. During a load disturbance test with a drop from 50% (5 Nm) to zero at 2.5 seconds, both controllers reached a similar overshoot peak (about 600 rpm); however, the Fuzzy PI controller stabilized back to 500 rpm within 0.3 seconds, significantly faster than the 0.8 seconds of the conventional PI controller. Additionally, the Fuzzy PI controller reduced current oscillations (±4 A versus ±6 A), further affirming its superior dynamic response and precision. These results validate the Fuzzy PI control strategy's effectiveness in optimizing PMSM performance, offering a robust framework for advanced control applications.
- PublicationCopper oxide nanocrystals based electrospun nanofibrous membrane for solar water evaporation(2024-03-01)Solar water evaporation has attracted widespread research, which narrowed the huge gap between inadequate clean water supply and human needs. For membrane evaporators, improving the solar absorption, water supply ability, and thermal management are critical to photothermal performance. Developing a suitable structure of light absorbing material could be a feasible approach to address these problems and to enhance evaporation performance. Yet there is limited research focus on this topic. In this study, three different structural CuO-based membrane evaporators were developed to adjust the membrane properties for improving solar evaporation performance. First of all, a triple-layer P/CuO-nanocluster nanofibrous membrane was fabricated through electrospinning, heating and hydrothermal processes. The top and bottom hydrophilic layers of CuO-nanocluster can effectively absorb sunlight, transport water, and suppress salt accumulation on the membrane surface. The middle layer of nanofibrous PVDF-HFP thin-film can support the whole system. The resultant membrane showed an evaporation rate of 1.21 kgm−2h−1 and efficiency of 83.57% for 3.5 wt.% saline water, which is higher than control group without membrane of 0.24 kgm−2h−1 and 16.26%, respectively. The next membrane structure design was core-shell structural P/CuO-Ag NPs nanofibrous membrane. During the electrospinning process, hydrophilic PVP was introduced to help more CuO growth media penetrating into the membrane interior during hydrothermal process. The Ag NPs incorporation enhanced membrane light absorption and wettability. The resultant core-shell P/CuO-Ag membrane achieved better evaporation rates of 1.31 kgm−2h−1 and efficiency of 90.77% for 3.5 wt.% saline water. The final membrane structure was hollow structural P/CuO-C nanofibrous membrane synthesized through coaxial electrospinning. During the fabrication process, the spinning precursor mixed with C NPs in the shell layer to enhance the light absorption while the hydrophilic PVP in the core layer was removed in the hydrothermal step to form a hollow structure. The formation of the hollow structure not only enhanced light absorption but also improved thermal management capacity of the membrane. As a result, the hollow structural P/CuO-C membrane achieved the best evaporation rate of 1.36 kgm−2h−1 and efficiency of 93.07% for 3.5 wt.% saline water as compared to the previous two structures. The outcome of this work will inspire subsequent research to construct of suitable architecture materials for potential applications in water treatment, thermal insulation, energy generation, energy storage, and other related fields.
- PublicationStreamflow prediction for sungai kulim, malaysia using random forest (rf) and support vector regression (svr) models(2024-05-01)Short-term streamflow prediction is important for managing immediate risks associated with extreme and unpredictable weather events. Despite numerical models showing great capabilities in streamflow prediction, they require extensive data, fundamentals of hydrology, and calibration efforts. Conversely, data-driven models are relatively quick to model and can capture the non-linearity in the streamflow time series, without requiring knowledge about the natural catchment mechanism, thus gaining traction in recent years amidst digital evolutions. In this study, two machine learning (ML) models, namely random forest (RF) and support vector regression (SVR) were introduced for multi-step ahead streamflow predictions in the Sungai Kulim catchment which has undergone speedy urban development. The models with six different input combinations were developed and assessed, using 14 years of hydrological datasets. The results revealed that the performance of the non-parametric RF algorithm was high depending on the size of terminal nodes and input configurations. Increasing the terminal node’s size improved the accuracy of the RF model. The maximum relative improvements in RMSE and NSE were 36.9% and 60.6% respectively, considering lead time up to three hours. Introducing more correlated variables into the input makes the RF algorithm capture the dynamics in time series, resulting in higher generalization to new and unseen data. Conversely, the performance of the SVR algorithm was more dependent on the selection of kernel functions and its hyperparameters, rather than the input combinations. Next, the RF model (Nash-Sutcliffe Efficiency (NSE):0.392-0.963; root mean square error (RMSE):1.485 m3/s-5.720 m3/s) performed better than the SVR model (NSE:0.190-0.830; RMSE:3.020 m3/s-6.598 m3/s) during both validation and verification stages. Although the peak streamflow was underpredicted by both RF and SVR models at all lead times, the RF model still resulted in very good predictions (PBIAS < 10%). However, the predictions by the SVR models were unsatisfactory (PBIAS > 25%), except for the one-hour-ahead streamflow (PBIAS=5.28%). The hydrographs reproduced by the RF model had smoother crest segments, rising and recession limbs as well as closer peak values, compared with the SVR model. In brief, the overall accuracy of the ML models decreased with the increasing lead-time length. The findings of this research provide insight into the use of ML algorithms for short-term streamflow prediction in Malaysia. This supports the goals of the Sendai Framework and Sustainable Development Goals by issuing flood warnings, informing risk reduction strategies, and enhancing disaster preparedness. It fosters resilient communities, safeguards human health, promotes sustainable water management, and addresses climate change impacts, contributing to safer and more sustainable development.
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- ItemGrowth Of Single-Walled Carbon Nanotubes Through Pengethanol Colloidal Solution(2011-10)Since the discovery of carbon nanotubes (CNTs), powder form catalyst support becomes the dominant in this field. But powder form catalyst support possesses some shortcoming such as difficulty in catalyst size monitoring and required subsequent purification. In this study, CNTs were grown over iron nanoparticles prepared by spin coated iron nitrate that diluted in colloidal solution of absolute ethanol and polyethylene glycol (PEG). The colloidal solution was later spin coated on silicon wafer and through catalytic chemical vapor deposition (CCVD) to grow CNTs. This approach competently overcomes the shortcomings aforementioned. In order to understand the effects of various process parameters on the topography of iron nanoparticles obtained and morphology of the as-grown CNTs, all the process parameters were studied separately. The parametric study was done in three stages, representing colloidal solution (composition of colloidal solution and concentration of iron nitrate), spin coating (spin speed, angular acceleration and spin period) and CCVD (reaction temperature, methane partial pressure and reaction period) study. Iron nitrate with concentration of 40mmol/L diluted in colloidal solution at a ratio 1:1 (v/v) of absolute ethanol to PEG-400, spin coated on silicon wafer at 8000 rpm for 30 seconds and under angular acceleration of 300rpm/sec was the best parameter to distribute iron nanoparticles evenly and in small size. This catalyst sample could grow single-walled CNTs (SWCNTs) with the highest selectivity and uniformity in diameter. Piranha solution was found useful to render the hyrophobicity of silicon oxide by introducing –OH group on the wafer. The –OH group was found could form a weak bond with PEG, providing force to reduce the surface tension. This led to the formation of catalyst nanoparticles of more uniform distribution. In CCVD, the best operating parameter to growth SWCNTs with highest uniformity and selectivity was at 850ºC under methane partial pressure of 0.333atm for 30 minutes. All three parameters were crucial to synthesize SWCNTs with high selectivity and crystallinity. The ratio of pre-growth catalyst size to the SWCNTs diameter was 2.3, while the ratio decreased to 1.38 for post growth catalyst used for comparison. Bigger the average size of catalyst nanoparticle resulted CNTs with wider distribution of diameter and also higher the ratio between the average catalyst nanoprticles to CNTs diameter. Finally, the crystallographic structure of the catalyst was also demonstrated as well. The iron nanoparticle was found to be converted to iron carbide after the growth of CNTs. The crystal structure was uniform throughout the whole catalyst particles. The decomposition of carbon sources on the surface of the iron and the dissolved carbon might diffuse to the center of the catalyst to achieve supersaturation and started the nucleation of CNTs. This work has successfully demonstrated a simple, novel and cost effective route to synthesize SWCNTs with high quality.
- PublicationEquivalent diagonal strut coupled with hybrid plasticity approach for seismic response macro-modelling of clay brick wall infilled frames(2020-11-01)Interaction between reinforced concrete frames and masonry infills under seismic load in Malaysia is often being overlooked by engineers and experts due to the low occurrence and magnitude of earthquake and scarcity of established research studies in the related area. Moreover, no guidance is given by Eurocode 6 and Eurocode 8 on macro-modelling approach of the seismic response of infilled frame. This study aims to provide an in-depth understanding on the seismic behaviour of masonry infilled reinforced concrete frames in Malaysia and to propose macro-modelling for masonry infilled frame through equivalent diagonal strut coupled with hybrid plasticity approach. Under the experimental testing, six half scale single-storey single-bay reinforced concrete frames with and without unreinforced clay brick infills were subjected to lateral monotonic and cyclic loadings. The seismic behaviour of the frame system improved in terms of strength, initial stiffness, energy dissipation and also delay in cracks formation in frame due to the presence of infill. However, the adopted masonry wall system is considered strong, thus induces shear failure in columns. It is discovered that effect of aspect ratio of infilled frame is significant in energy dissipation. Macro-Modelling of masonry infilled reinforced concrete frames using equivalent diagonal strut coupled with hybrid plasticity approach and an improved constitutive backbone law shows good correspondence with experimental result. Under the investigation of reliability of seven equivalent diagonal strut width models using the improved constitutive backbone law, it is discovered that models with similar strut width trends over aspect ratio produce similar responses. All the strut models are able to produce response with reasonable accuracy except Mainstone (1974) model. Seismic performance of a five-storey non-ductile masonry infilled reinforced concrete frames typically found in Malaysia was assessed using incremental dynamic analysis (IDA) with ten ground motion records. The collapse capacity at 16%, 50% and 84% fractiles of IDA curves are 1.0, 1.53 and 2.03, respectively. The maximum drift ratio where dynamic instability is reached ranges between 0.1% to 0.26%. This study has provided a practical elucidation of the interaction between infill and frame for the development of more realistic seismic-resistant design for Malaysia.
- ItemThe Effects Of Bacillus And Lactobacillus As Probiotics On Mud Crab Scylla Paramamosain (Estampador, 1949) Zoea Larval Culture Performance(Universiti Sains Malaysia, 2016-03)Mud crabs (Scylla spp.) are commercially important crustaceans. One of the major obstacles to the growth of Scylla aquaculture is the low supply of hatchery produced seed due to bacterial diseases and high rates of mortalities. Currently, antibiotics are used extensively in Scylla larval culture to improve survival, but its use poses numerous risks including the development of resistance in bacteria to antibiotics, higher levels of virulence, and detection of restricted chemicals in the flesh of farmed animals. The aim of this study was to determine the culture performance of Scylla paramamosain larvae with the use of three different types of probiotics, namely a multispecies Bacillus, Lactobacillus casei (Shirota), and Lactobacillus plantarum, at various concentrations. There were higher average larval survivals in treatments with a multispecies Bacillus probiotics added compared with the control, especially at concentrations of 5.00 × 108 (12.33 - 18.33 ± 1.76 - 3.76 % compared to 1.67 - 3.67 ± 1.67 - 1.76 %; P < 0.05) and 1.00 × 109 cfu/ml. The best concentration of the multispecies Bacillus probiotic that gave lower Vibrio parahaemolyticus counts in this study was at a concentration of 1.00 × 109 cfu/ml. This was significantly lower than the control (1.33 ± 1.33 cfu/ml compared to 32.67 ± 11.05 cfu/ml) during the later days post hatching (DPH). Vibrio parahaemolyticus is known to be pathogenic to Scylla larvae, thus lower numbers are desirable in culture. On average, there were no obvious differences in water qualities and Larval Stage Indexes (LSIs) between the multispecies Bacillus treatments and controls, although larvae appeared healthier in the multispecies Bacillus treatments. Water qualities were within tolerable ranges for Scylla larvae. The fastest larval developmental stage was seen in the multispecies Bacillus treatment at 1.00 × 109 cfu/ml. Lactobacillus casei treatments at concentrations of 1.88 × 108 and 3.75 × 108 cfu/ml gave significantly higher survival rates compared to the control during the early to mid DPHs (49.70 - 99.30 ± 11.90 - 29.20 and 70.70 ± 13.03 % compared to 2.30 - 5.70 ± 1.20 - 5.70 %, respectively; P = 0.022 and 0.029). There were significantly higher survival rates in the Lactobacillus plantarum treatments compared to the control during the early DPH (74.33 - 90.67 ± 7.26 - 6.57 % compared to 47.67 ± 2.19 %; P = 0.040 and 0.005), at concentrations of 1.00 × 102 and 5.00 × 102 cfu/ml in the culture water. In terms of water qualities and LSIs, there were no obvious differences between the Lactobacillus treatments and controls, and this could be due to the relatively low concentration of Lactobacillus added. Based on the concentrations used in this study, the multispecies Bacillus probiotic was more effective than single species Lactobacillus for improving the survival rate and lowering V. parahaemolyticus counts of S. paramamosain larvae. The recommended concentration of the multispecies Bacillus to be added into S. paramamosain larvae was therefore 5.00 × 108 and 1.00 × 109 cfu/ml, and for Lactobacillus it was 3.75 × 108 cfu/ml. The use of Bacillus and Lactobacillus as probiotics is an ideal alternative to antibiotics in Scylla hatcheries to provide a consistent, commercially feasible production of seedlings.
- ItemImpact Of Traditional Prognostic Factor And Chemotherapy Schedule Modification On Breast Cancer Patients: A 5 Year Retrospective Study In A District Specialist Hospital In The State Of Perak(Universiti Sains Malaysia, 2021-10)Chemotherapy schedule modifications are done in clinical practice due to treatment complications or the patients preference. Multiple clinical studies have established the negative prognostic impact of dose delay on survival rates. This study aims to investigate the prevalence and reason for chemotherapy schedule modification with the impact of schedule modification on the Overall Survival (OS) of the breast cancer patient. This retrospective cohort study was done among breast cancer patients receiving chemotherapy from 2013 to 2017 and was followed until 31 Dec 2018. Medical records of patients with cancer were reviewed. Inclusion criteria involved the female patients over eighteen years old, primary carcinoma of the breast, received Anthracycline or Taxane based chemotherapy regimen and completed more than two cycles of chemotherapy. Patients were categorised into three categories of no schedule modification, with schedule modification, and incomplete schedule. The Kaplan-Meier were used to test for survival differences in the univariate setting, and the Cox regression model was used in the multivariate setting. This study aims to measure the prevalence, OS rates, and Hazard Risk (HR) of these three treatment categories. Among 171 patients receiving chemotherapy, 28 (16.4%) had no schedule modification, 118 (69.0%) had schedule modification, and the remaining 25 (14.6%) had an incomplete schedule with OS of 75.0%, 59.3%, and 52.0%, respectively
- ItemSynthesis and properties of novel poly(alkyd-urethane)s derived from various types of vegetable oils(2014)Triglyceride of oil palm (Elaeis guineensis), soy (Glycine max) and sunflower (Helianthus annuus) were used to produce novel alkyd diols and poly(alkydurethane) s with chemical structure specifically designed for better coating performances. The vegetable oils were first converted to monoglycerides by glycerolysis process. The monoglycerides derived from the different oils were reacted with phthalic anhydride at 2:1 monoglyceride-to-phthalic anhydride ratio to obtain novel polyols called alkyd diols. The polyols were then reacted with 4,4`- methylenediphenyldiisocyanate (MDI) to produce five novel poly(alkyd-urethane)s (PAU), namely palm oil based poly(alkyd-urethane) (POPAU), soy oil based poly(alkyd-urethane) (SOPAU), sunflower oil based poly(alkyd-urethane) (SFPAU), palm-soy oils based poly(alkyd-urethane) (POSOPAU) and palm-sunflower oils based poly(alkyd-urethane) (POSFPAU). The successful synthesis of the monoglycerides, alkyd diols and poly(alkyd-urethane)s were confirmed by FTIR, 1H NMR, 13C NMR spectroscopy and their morphology were evaluated by scanning electron microscopy (SEM). The obtained varieties of poly(alkyd-urethane) were applied onto substrates to study their physical and mechanical properties. Further analyses prior to application included viscosity, solubility, iodine number testing, gel content, drying time test while thermogravimetric analysis (TGA), crosshatch adhesion tests, impact strength, pencil hardness, chemical and water resistance were employed after the films were cured. The films showed good homogeneity and impressive thermal stability with palm oil poly(alkyd-urethane) showing only 5% weight loss temperature in N2 at 270oC. Overall, sunflower oil poly(alkyd-urethane) exhibited relatively better mechanical and thermal properties among all due to the highest percentage of cross linked fraction portrayed by its higher iodine value and gel content. Coating performance of poly(alkyd-urethane) based on palm oil was enhanced after blending with sunflower oil or soy oil based alkyd-diols. The adopted technique in the novel chemical design of poly(alkyd-urethane)s created a potential alternative reaction schemes to be applied in the industry for surface coating, binder for composites and other applications, aiding the effort to replace or minimize the use of non-sustainable petroleum-based raw material.