Universiti Putra Malaysia
  • Putrajaya, Selangor, Malaysia
Recent publications
This study investigated the antimicrobial activity of the green synthesis copper oxide nanoparticles (CuO-NPs) from Eucalyptus Globulus leaf extract against S. sonnei clinical isolates and the reference strain S. sonnei ATCC 9290 alone and in synergy with antibiotics. Biosynthesized NPs analyzed for shape, size, and crystal nature. The antimicrobial genotype and phenotype characteristic for selecting the most resistant isolates from 30 S. sonnei clinical isolates performed through the distribution of ipaH, sigA, and virF, CTX-M-1, CIT group, aac(6’)-Ib-cr genes by polymerase chain reaction (PCR) technology and Kirby-Bauer susceptibility test. The minimum inhibitory concentration (MIC) of CuO-NPs against S. sonnei was determined within 0-360 min treatment time. The double-disc method was performed for semi-sensitive and antibiotic-resistant strains to evaluate the probable inhibitory effect in synergy form. XRD, TEM, and FTIR analysis confirmed the successful synthesis of NPs with appropriate purity, shape, and size. Only one of the S. sonnei isolates was positive for all MDR-related genes (blaCTX-M-1 and blaCIT, aac(6’)-Ib-cr) and showed the highest susceptibility reaction against CuO-NPs, Z=312.5 mL.µg-1 in comparison to Z=256.25 mL.µg-1 for the standard strain, and the process continued by performing the optimal ratio of NPs on semi-sensitive and also resistance antibiotic in synergy with NPs for the bacteria isolated. Furthermore, the synergy effect of CuO-NPs with Oxacillin, Chloramphenicol, Imipenem, and Levofloxacin was higher than using antibiotics alone. CuO-NPs, enhance the properties and characteristics of antibacterial potency in synergy or developed synthetic functionalized NPs with antibiotics.
Oil palms are extensively planted in tropical countries and causing a severe decline in biodiversity. Alley-cropping is an agroforestry practice that has been proven to sustain greater diversity of terrestrial arthropods than monoculture plantations. However, the environmental factors responsible for these differences remain unclear. This study aimed to identify the environmental factors influencing terrestrial arthropod abundance and richness in alley-cropping and monoculture oil palm plantations. We sampled terrestrial arthropod using 840 pitfall traps under seven treatments: oil palm alley-cropping systems with Bactris, bamboo, black pepper, cacao, and pineapple; and two oil palm monoculture systems. We assessed the microenvironment (presence/absence of alley cropping, vegetation coverage, soil surface temperature, soil moisture, light intensity, and relative air humidity) at each sampling site. Overall, 14,358 arthropods belonging to 19 orders were collected. The presence of alley-cropping was the only factor that positively affected the arthropod abundance and order richness. Arthropod abundance was negatively affected by soil moisture, suggesting that the dominant species, even in alley-cropping, were generalist species acclimated to dry soil conditions. Our study suggests that alley-cropping in oil palm plantations could increase the terrestrial arthropods diversity by increasing the diversity of vegetation (even with only one additional crop), rather than improving habitat microclimate. However, as microclimate remained intense, alley-cropping with only one secondary crop in our study site would not be sufficient to conserve forest specialist species. We suggest that producers of oil palm pay close attention to the potential of alley-cropping incorporating multiple secondary crops to increase biodiversity in plantations.
Climate change has impacted agricultural production systems, especially in the Sahel region, which is fragile climatically, politically, and economically. This region is of particular concern due to its rising population and strategic importance on the African continent. Our review focused on the impact of climate change on millet production in the Central Sahel and aimed to identify adaptation strategies by the farmers. This review shows that increased temperature has a negative impact on millet yield and growth parameters. Other climatic factors significantly affecting millet production in the Central Sahel include drought, desertification, dry spells, rainfall variability, and wind. Projected data suggests a decline in millet production in northern, central, and western Mali by 21%, 20%, and 18%, respectively, by 2030. Additionally, there is an anticipated 17% decrease in pearl millet production in Sub-Saharan Africa by 2050 under future climate change projections. Nevertheless, farmers in the Central Sahel have devised a variety of indigenous climate change adaptation strategies to sustain millet production. These adaptation strategies encompass Zai, half-moon, stone-line, and intercropping. These adaptation practices have proven effective in mitigating the effects of climate change on millet production in the Sahel region. This review suggests strengthening farmers' adaptive capacity to climate change, promoting regional knowledge, integrating millet as a fundamental crop group for food security in the Central Sahel, adopting zero-tillage or minimum-tillage practices during crop production, diversifying crops, and providing heat- and drought-tolerant crop varieties. Impact of climate variables on millet production
In this research, a novel eco-friendly green composite is fabricated by combining a biomatrix composed of a biopolymer, date palm fiber, and a filler obtained from discarded eggshell (ES) waste material. This research aims to check the influent of ES filler on thermal and viscoelasticity properties of bio-epoxy composite with incorporation of 40 wt.% date palm (DP) fiber. Various ES filler ratios, specifically 5 wt.%, 10 wt.%, 15 wt.%, and 20 wt.%, are dispersed into the composite. Thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA) approach were employed to investigate the properties of fabricated composites as a function of temperature in terms of storage modulus (E′), loss modulus (E′′), Tan delta (Tan δ), glass transition temperature (Tg), and Cole-Cole plot. Overall, incorporating ES filler into the bio-epoxy/DP fiber composites increased E′, E′′, and Tg significantly. ES-filled composites containing 5 and 10 wt.% exhibited properties comparable to 15 wt.% but less than 20 wt.% ES filler. Thermal tests result show that 20 wt.% ES-filled materials outperform their counterparts in terms of heat resistance or thermal stability. The evidence suggests that the embodiment of ES filler in bio-epoxy/DP fiber composites yields enhancements in both thermal and dynamic mechanical properties. This indicates the potential for utilizing ES filler loading in advanced composite applications that prioritize thermal stability and sustainability
The prevalence of house dust mite (HDM) allergy, especially in Asian countries with rapid urbanization, has been increasing. House dust mites thrive in places with relatively high humidity. With the combination of climate change, naturally high humidity, and urbanization, tropical countries like Malaysia are becoming a hotspot for HDM allergy fast. With a previously reported sensitization rate of between 60 and 80%, it is a worrying trend for Malaysia. However, due to incomplete and out-of-date data, as seen by the limited study coverage in the past, these numbers do not paint a complete picture of the true HDM allergy scene in Malaysia. This review briefly discusses the HDM fauna, the HDM sensitization rate, the common diagnosis and therapeutic tools for HDM allergy in Malaysia, and makes suggestions for possible improvements in the future. This review also highlights the need of more comprehensive population-based prevalence studies to be done in Malaysia, encompassing the three main HDMs—Dermatophagoides pteronyssinus, Dermatophagoides farinae, and Blomia tropicalis—as the lack of up-to-date studies failed to give a clearer picture on the current scenario of HDM allergy in Malaysia. Future studies will be beneficial to the nation in preparing a better blueprint for the management and treatment of HDM allergy.
One of the most widely referenced Swarm Intelligence (SI) algorithms is the Grey Wolf Optimizer (GWO), which is based on the pack hunting and natural leadership organization of grey wolves. The GWO algorithm offers several significant benefits, including simple implementation, rapid convergence, and superior convergence outcomes, leading to its effective application in diverse fields for solving optimization issues. Consequently, the GWO has rapidly garnered substantial research interest and a broad audience across numerous areas. To better understand the literature on this algorithm, this review paper aims to consolidate and summarize research publications that utilized the GWO. The paper begins with a concise introduction to the GWO, providing insight into its natural establishment and conceptual framework for optimization. It then lays out the theoretical foundation and key procedures involved in the GWO, following which it comprehensively examines the most recent iterations of the algorithm and categorizes them into parallel, modified, and hybridized variations. Subsequently, the primary applications of the GWO are thoroughly explored, spanning various fields such as computer science, engineering, energy, physics and astronomy, materials science, environmental science, and chemical engineering, among others. This review paper concludes by summarizing the key arguments in favour of GWO and outlining potential lines of inquiry in the future research.
Recently, the trend in solar cell research has become highly competitive, with researchers striving to find the best material that strikes a balance between various factors, including fabrication speed, cost, material toxicity, abundance, and overall photovoltaic performance. Typically, cadmium sulfide serves as the buffer layer in CZTS solar cells, but this material is known for its high toxicity. On the other hand, zinc tin oxide (ZTO) has gained popularity in solar cell applications due to its transparency, conductivity, thermal stability, and non-toxic nature. Consequently, the idea of using ZTO as an alternative buffer layer in CZTS solar cells has emerged. In this study, we synthesized nanocomposite thin films of Zn(1−x)SnxO (x = 0.100, 0.133, 0.167, 0.200, and 0.233% w/w) using the sol–gel method and spin coating technique. Among the various concentrations tested, the thin film composed of Zn0.833Sn0.167O demonstrated the highest power conversion efficiency (PCE) of 0.54%. This outcome marked a successful result, indicating that this particular composition optimizes efficiency in our study. It is noteworthy that excessive tin doping did not lead to improved efficiency. However, it is important to acknowledge that the PCE in our experiment is relatively low compared to that of other researchers due to the use of ITO glass as the back contact, chosen for economic considerations. Furthermore, our fabrication method for ZTO thin films resulted in a bandgap energy (Eg) value of 0.78 eV. In summary, our findings suggest that ZTO has the potential to replace cadmium sulfide as the buffer layer in CZTS-based solar cells. These findings are expected to have a significant impact on promoting ZTO as the primary buffer material in CZTS solar cell technology.
In this paper, we propose a sparse equity portfolio optimization model that aims at minimizing transaction cost by avoiding small investments while promoting diversification to help mitigate the volatility in the portfolio. The former is achieved by including the ℓ0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$\ell _{0}$\end{document}-norm regularization of the asset weights to promote sparsity. Subjected to a minimum expected return, the proposed model turns out to be an objective function consisting of discontinuous and nonconvex terms. The complexity of the model calls for proximal method, which allows us to handle the objective terms separately via the corresponding proximal operators. We develop an efficient algorithm to find the optimal portfolio and prove its global convergence. The efficiency of the algorithm is demonstrated using real stock data and the model is promising in portfolio selection in terms of generating higher expected return while maintaining good level of sparsity, and thus minimizing transaction cost.
This study examines how the nomenclature of street food names includes trans-local, trans-regional, and trans-national scales in local language resources. The study adopts a qualitative case study on street food names in Malaysia. The study sample comprised 856 street food names collected in Kuala Lumpur. The food nomenclature framework and the concepts of trans-local, trans-regional, and trans-national scales were adopted to elicit the data. It was found that: (i) there are more complex combinations based on ingredient, cooking method, food attribute, commemorative aspect, and good name; (ii) there are scale-making ways, via the presentation and the transliteration of street food elements. In conclusion, the nomenclature of street food names labels Malaysia as a multiscalar locality in which trans-local, trans-regional, and trans-national scales can be discerned. Thus, this study reveals how nomenclature shapes and is shaped by geographical scales. Therefore, it contributes to the nomenclature of food and place marketing.
A surfactant-assisted co-precipitation method was used to prepare the catalysts Co,Ni,Pd/CaO, Co,Ni,Pd/Ca0.97La3+0.03O, Co,Ni,Pd/Ca0.93La3+0.07O, and Co,Ni,Pd/Ca0.85La3+0.15O (1% each of Co, Ni, and Pd). La2O3 doping effect on the activity and stability of Co,Ni,Pd/CaO catalysts was investigated in dry reforming of methane. Catalysts were characterized by several techniques (X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), X-ray Fluorescence (XRF), Fourier Transform Infra Red (FTIR), Temperature Programmed Desorption H2 (H2-TPR), Transmission electron microscopes (TEM), and Temperature Gravimetric Analysis (TGA)) and were tested in a fixed-bed reactor at 900 °C and (Gas Hourly Specific Velocity (GHSV) = 15000 mL.gcat−1.h−1, atmospheric pressure). Adding La2O3 had little effect on the morphology of the Co,Ni,Pd/CaO catalyst. However, it played a crucial role in enhancing the catalyst’s reducibility and CO2 adsorption at high temperatures, as indicated by the activity and stability of the Co,Ni,Pd/CaO catalyst. The carbon deposition on utilized catalysts after 5 hours at 900 °C was examined using TEM and thermal gravimetric analysis (TGA) techniques. Compared to Co,Ni,Pd/CaO catalysts across the entire temperature range, the tri-metallic Co,Ni,Pd/Ca0.85La3+0.15O catalyst with a lanthanum promoter demonstrated a greater conversion of CH4 (84%) and CO2 (92 %) at a 1:1 CH4:CO2 ratio. The selectivity of H2/CO reduced in the following order: Co,Ni,Pd/Ca0.85La3+0.15O > Co,Ni,Pd/Ca0.93La3+0.07O > Co,Ni,Pd/Ca0.97La3+0.03O > Co,Ni,Pd/CaO. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).
Preschool teachers can play a critical role in early detection of autism. Equipping preschool teachers with prerequisite knowledge and skills would allow them to identify children with probable autism and referral to diagnostic services. This study aimed to investigate the impact of an educational module (EMiASD) that prepared preschool teachers to identify autism symptoms. The sample included 144 preschool teachers, of which 120 were stratified and randomly assigned to an intervention arm receiving training in EMiASD (n = 60) or a comparison arm receiving standard training (n = 60) using a parallel mixed-methods design. Responses to open-ended questions about video case studies revealed improvement in the identification of autism symptoms in preschool teachers in the intervention arm, in contrast to preschool teachers in the comparison arm. Moreover, significant changes in knowledge, belief, and self-efficacy about autism favoured EMiASD. Overall, these results demonstrate the influence of EMiASD in the Yemeni cultural context.
Urban poor children have low vegetable consumption due to food insecurities leading to limited access to vegetables. Children's involvement in gardening may improve their vegetable consumption and connection with nature. This qualitative study explored the potential facilitators and barriers related to vegetable consumption and gardening among urban poor children in Kuala Lumpur, Malaysia. Four focus group discussions were conducted among 20 randomly selected children aged 9–12 years, residing in selected low‐cost flats in Kuala Lumpur, Malaysia, from November 2021 to January 2022. Thematic analysis via NVivo software was conducted to analyse the transcripts. Children reported several barriers to eating vegetables, such as disliking taste, sensory and appearance, limited accessibility and vegetable availability at home. Most children felt positive and interested to join gardening. The findings are useful in planning nutrition intervention programmes that incorporate gardening as one of the elements to improve vegetable consumption.
The aviation industry is attempting to enhance the aerodynamic performance by increasing the aspect ratio of the wing, which can be associated with the usage of the High Aspect Ratio (HAR) wing. Aerodynamic performance can be analyzed using different approaches and one of the approaches is through the Computational Fluid Dynamics (CFD) analysis. However, prior research demonstrates a vague technique for CFD analysis, which makes it challenging for new researchers to learn the precise steps using the CFD approach. Therefore, this study aims to demonstrate the process of CFD analysis in a detailed technique using Ansys software and compare the aerodynamic performance at three options domain sizes. The aspect ratio of AR-16 was used with the Spalart–Allmaras turbulence model and the result of the mesh independency study was validated with the lift coefficient. The best mesh was verified with different turbulence models either using k–ω SST or Standard k–ε. The result shows that the best mesh for the HAR wing is the base mesh with a low percentage difference compared to fine mesh. In the domain sizes, the second option with the reduction of 20% domain size produced a higher lift-to-drag ratio than first and third options with a percentage error of less than 6% at the angle of attack, AoA 9°. Moreover, the 20% domain size reduction can reduce approximately 20 min of computational time, as well as contribute to the computational time efficiency in the CFD analysis of the HAR wing.
The flight performance and flight trajectory of any unguided rocket should be determined because its capability and flight trajectory are uncountable in flights. The purpose in this study was to develop a performance and trajectory prediction program for an unguided 2.75-inch solid propellant rocket and to perform a parametric analysis. The program uses the Runge–Kutta Fehlberg (or RKF45) method, and it was developed using Python. It requires multiple geometric designs and motor parameters as the program input. The program was then verified and validated with previous experimental flight data obtained from literature papers. Then, a parametric analysis (also called as sensitivity analysis) was done to analyze how significant these parameters affect the flight of a rocket, compared with the results based on the baseline rocket. Based on the prediction results, the baseline rocket flies with a range of 3040 m, reaches up to 3307 m in altitude and has a peak velocity of 747.554 m/s. In parametric analysis, the parameter that gave the most significant difference was motor grain configuration, followed by launch angle and nozzle expansion ratio.
The development of a supersonic flow in the air intake is critical to the operation of a scramjet engine since it determines how well the engine performs. The configuration of the air intake plays a key role in determining whether or not the required pressure recovery of the intake is attained, which in turn affects the efficiency of the combustion chamber. This work presents the prediction of aerodynamics performance of scramjet’s intake at high Mach number flight using computational fluid dynamics. A scramjet intake with mixed compression is being used, and it has two external ramps. The work focused on the aerodynamics characteristics of the intake and the effects of the cowl lip length on the compression ratio inside isolator. CFD simulation was modelled for 2-dimensional, steady, compressible flow using rhoCentralFoam of OpenFOAM. The Mach numbers were ranged from 5 to 6.5, angle of attacks (3°, 0°, and −3°) and flight altitude of 26 km. The results show an improvement in compression ratio (static pressure, and static temperature) up to 20% in addition to increment in mass flow captured by 16.7%.
Due to the evolution of advanced technologies and their broad range of applications in numerous domains such as military, industrial, and scientific purposes, worldwide interest in High Altitude Platform Stations (HAPS) continue to rise. Researchers and experts worldwide have taken the initiative and conducted studies to create and build high-efficiency and safe HAPS. However, far too little attention has been paid to designing HAPS by embedding cylinders into a flat plate. The primary concern of the design is whether the approach of injecting the Magnus effect would be able to improve the aerodynamics and stability of the flat plate. To date, a new Cylinder to Flat Plate to Cylinder (CyFlaP) HAPS has been designed that incorporates the Magnus effect on a bluff body with the goal of increasing its aerodynamic performance. This project intends to analyze the pitching moment coefficient due to the rotational direction and rotational speed of the rotating cylinders. The tests were conducted for different Reynolds numbers (Re) ranging from Re = 2.55 × 105 to 9.10 × 105 which implicitly implied different free stream velocities varying from 2.80 to 10.05 m/s for different angles of attack ranging from α = −20° to α = 20°. Data for this study were collected using experimental analysis of the model in the closed-loop wind tunnel. Among the documented data, only the ones that had a higher rotational speed with clockwise rotating cylinders displayed a negative slope of moment coefficient over the specified range of angle of attack, with the highest negative moment coefficient recorded to be \({C}_{M}\) = −0.04 at the angle of attack, α = 10°. The analysis shows that the CyFlaP is able to fly in a longitudinal static stable state at 10.05 m/s (Re = 9.10 × 105) when the rotating cylinders are rotated in the clockwise-clockwise direction at a speed of 2322 RPM. This highlights the capability of the CyFlaP to fly steadily.
An airfoil is used in many engineering applications for its ability to create high aerodynamics performances compared to other shapes. However, airfoils also produce annoying noise, and consequently has degraded its usage near the residential area. The study on airfoil noise prediction is very challenging, either experimentally or numerically. Background noise and identifying detailed noise sources are the common problems in experimental works while accurate prediction of small fluctuating pressure requires huge computational resources for numerical noise prediction. This study evaluates the performance of Detached Eddy Simulation (DES) as the turbulent modelling approach in predicting the noise source of a NACA 0012. The noise calculated from DES is compared with RANS and the experimental results. The study showed that the DES turbulence model is able to capture peak frequency at 300 to 600 Hz, similar to the experimental result. Additionally, DES provides better accuracy than RANS turbulence model by eliminating the sudden peak captured by RANS at a higher frequency. However, DES turbulence model still does not capture the good trends in the high-frequency region above 800 Hz because this turbulence model is a hybrid of RANS and still becomes the dominant influence in the DES calculation in the near-wall region.
Boxfish’s unusual rigid-like shape is commonly thought as the limitation of its movement within its aquatic surroundings. Despite that, recent studies on its hydrodynamic characteristics has proved its hydrodynamic capability with some claiming that the unique boxfish shape produces less drag and helps maneuverability. These qualities are desirable for hydrodynamic and aerodynamic vehicles. Applying a biomimetic approach, this attempts to adapt the boxfish shape to airship design in order to improve its flight performance. A boxfish-shaped airship hull is designed with an approximation of the carapace shape of a yellow boxfish (Ostracion cubicus Linnaeus 1728). For aerodynamics characterization comparison, a typical ellipsoidal hull shape with a similar fineness ratio is chosen. Both airship’s hulls are analyzed using Ansys Fluent, a solver system for aerodynamic performance analysis with computational fluid dynamics approach. The drag force, lift force, yaw moment, and pitch moment is chosen as these are the qualities that relate to airship maneuverability. The results show that the boxfish-inspired airship’s hull generates better maneuverability in the yaw plane but higher drag association compared to the ellipsoid airship’s hull. Additionally, the boxfish-shaped airship’s hull promotes better stability in the pitch plane. This study demonstrates that the biomimetic airship’s hull has huge potential in the airship’s development. It is hoped that study will provide useful resources for future development of biomimetic application in lighter-than-air vehicle design.
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22,217 members
Suet Lin Chia
  • Department of Microbiology
Habeeb Ibrahim Abdul Razack
  • Faculty of Medicine and Health Science
Mohamad Ibrani Shahrimin Adam Assim
  • Department of Social Science
43400, Putrajaya, Selangor, Malaysia