Stability and Hopf Bifurcation Analysis of a Simple Nutrient- Prey-Predator Model with Intratrophic Predation in Chemostat

A 3-dimensional nutrient-prey-predator model with intratrophic predation is proposed and studied. Some elementary properties such as invariance of nonnegativity, boundedness and dissipativity of the system are presented. The purpose of this chapter is to study the existence and stability of equilibria along with the effects of intratrophic predation towards the positions and stability of those equilibria of the system. We also investigate the occurrence of Hopf bifurcation. In the case when there is no presence of predator organisms, intratrophic predation may not give impact on the stability of equilibria of the system. We also analysed global stability of the equilibrium point. A suitable Lyapunov function is defined for global stability analysis and some results of persistence analysis are presented for the existence of positive interior equilibrium point. Besides that, Hopf bifurcation analysis of the system are demonstrated

Design of Crude Palm Oil Monitoring System using Electrical Capacitance Tomography: A Conceptual Framework

In Crude Palm Oil (CPO) milling operations, the oil flow that has gone through separation process must be tested for its purity as wastes (e.g. palm oil mill effluent, water, sludge) tend to get carried along the process pipeline. At present, this procedure usually takes up to 5 days as samples of the flow needed to be verified biologically for its composition. Electrical Capacitance Tomography (ECT) systems that are able to provide the cross-sectional images of a closed content has proven the possibility of monitoring the composition of CPO flow in online manner. ECT systems are also able to provide other crucial flow information such as its velocity and flow regime that could help in controlling the processes. In this paper, a brief literature review of existing ECT systems are presented, then a conceptual design for developing an ECT system for visualizing and measuring CPO flow are presented along with the decision process of choosing suitable technique and hardware types for the new ECT system for CPO monitoring. A preliminary simulation study of the capability of the designed system to reconstruct images of water-oil flow phantoms is also presented. The simulation results show that the designed system is capable of reconstructing phantom images with error lower than 30 %

Innovative Classroom Strategy: Impact on Students’ Mathematics Motivation, Anxiety and Achievement in Pre-University Studies

One aspect that influences mathematics achievement is students' mathematics motivation, which is closely related to their mathematics anxiety. This study aims to incorporate a classroom intervention strategy using a brain-based teaching approach (BBTA) with technological tools to improve students' mathematics performance in pre-university studies. BBTA was used in the classroom to increase students’ mathematics interest and minimise their mathematics anxiety to increase mathematics performance. Two hundred and six (206) pre-university students were exposed to both BBTA and conventional instructions during their Statistic lessons. Questionnaire comprises of motivation and anxiety-related questions as well as pre and post mathematics tests were administered to these students. Based on the findings, students with low anxiety appeared to have more self-confidence when studying mathematics, which simultaneously improved their examination results. These two elements are critical in students' learning of mathematics because students who have low levels of anxiety and high levels of motivation in learning mathematics attain high achievement in mathematics

Miniature parallel ECT: a preliminary study using comsol

The usage of Electrical Capacitance Tomography (ECT) is not limited to the imaging of mixtures in process equipment, it also can be used to measure the concentration profiles of component, and in certain case ECT is being used to investigate the boundaries and phase sizes within vessels and pipelines. There are quite a number of type of ECT sensors such as circular structure, square structure, concentric -annulus and parallel structure which are used for particular applications. In this paper, a study was carried out in order to investigate the behavior of electric field on the miniature parallel ECT. Simulations using COMSOL Multiphysics are being done to study the effect of increasing the size of the test object and the effect of increasing the permittivity of the test object. The results show that (1) the electric field lines relatively follow the phantom shape corresponding to the increasing of the size of the phantom and (2) the electrical field lines seems to bend more around the when the permittivity increases. Presented simulations establish first step of investigation, however already proved its usefulness for ECT performance model validation

Velocity measurement simulative study of twin plane ECT using advanced cross correlation technique

Flow velocity is a critical information to have in order to ensure an optimum flow condition in a process plant. The combination of Electrical Capacitance Tomography and cross correlation technique has been successfully used to measure the velocity of multiphase flows. The peak of the cross correlated signals corresponds to the time taken by particles to move along the flow, thus its velocity can be derived. This paper investigates the capability of implementing an improved method of determining flow velocity by using a combined function of the cross correlation (CCF) and average squared differential (ASDF) functions in order to improve the accuracy of the velocity measurement. A velocity measurement simulation of a liquid/gas flow using MATLAB is employed and a comparison between the use of CCF and the combination of CCF/ASDF is made. The correlogram of the combined CCF/ASDF method has a sharper peak compared to the correlogram of the conventional CCF method, indicating that the peak of the function can be determined more accurately as the sharper peak can decrease the measurement uncertainty

Scienceploration 2023

The Scienceploration Camp is an initiative of the Centre for Pre-University Studies, UNIMAS (PPPU), which aims to increase the interest in science among secondary school students. It is also an effort taken by PPPU towards the achievement of Sustainable Development Goals 4 in providing equal quality education and promoting lifelong learning opportunities for all. On top of that, this camp supports Sarawak’s Digital Economy Strategy in nurturing an integrated ecosystem to foster inclusive digital society, by building the right foundations to grow our local digital economy

A first look at monthly fluctuations of Sr/Ca in Porites sp. from The East and West Coast of Peninsular Malaysia

Coral cores were collected from four locations around Peninsular Malaysia and Sr/Ca ratios were measured. The interannual temperature ranges from 26.8-31.5°C. The sites chosen were Pulau Redang, Port Dickson, Pulau Tioman and Pulau Payar due to the Southeast Monsoon and Northwest Monsoon influences coupled with effects of the El Niño Southern Oscillation towards the region. Coral powder samples were sampled at 1 mm intervals along apex of extending corralites visible along the coral slab surface and analysed using ICP-OES. Ordinary least squares regression analysis showed that Sr/Ca ratios in cores from all sites have a significant negative relationship with sea surface temperature (SST). The correlation coefficients (r) were -0.704, -0.651, -0.667 and -0.600 for Pulau Payar, Port Dickson, Pulau Tioman and Pulau Redang, respectively. Values from the 2010 El Niño event were plotted against the total Sr/Ca vs SST data and decline in the regression slope was observed in the Pulau Payar core. Sr/Ca calibration using the linear least squares equation showed that the intercept (A) and slope (B) values from Pulau Tioman and Port Dickson are very similar to Sr/Ca–SST relationships generated from high resolution coral series in other studies

Effect of the welding speed on the macrostructure, microstructure and mechanical properties of AA6061-T6 friction stir butt welds

Friction stir welding of aluminum alloys has been progressively used in different industries on the ground of higher welding quality in comparison to fusion welding. In this article, friction stir welding of 6061-T6 aluminum alloy with 9.6 mm thickness was carried out by using three different welding speeds (63, 89 and 110 mm/min). The effect of welding speed on macro- and microstructure, micro hardness, tensile properties and kissing bond was investigated. Results show that the Low Hardness Zone was moved toward the weld center by increasing the welding speed. The average micro hardness in the weld nugget zone increased from 60.1 to 67.6 HV with the raise of welding speed from 63 to 110 mm/min. Thermo Mechanical Affected Zone was clearly revealed using Electron backscatter diffraction (EBSD). The kissing bond was studied by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) mapping. It was proven that the damaging effect of kissing bond was linked to location of this discontinuity, although the growth of kissing bond was linked to higher welding speed. The maximum value of Ultimate Tensile Strength (UTS) (159 MPa) was obtained at 110 mm/min, whereas the Yield Strength (YS) in the sample at 89 and 110 mm/min welding speed exhibit the same trend with 137 MPa and 134 MPa respectively

Solid-to-Liquid Ratio Influenced on Adhesion Strength of Metakaolin Geopolymer Coating Paste Added Photocatalyst Materials

Coating materials are used on surfaces such as steel and ceramic to offer protection, corrosion resistance, wear and erosion resistance, a thermal barrier, or aesthetics. Although organic coating materials such as epoxy resins, silane, and acrylic are widely used, there are restrictions and drawbacks associated with their use, including the ease with which cracking, hazardous and harmful human health and environment, peeling, and deterioration occur. Organic matrices also have the capacity to release vapor pressure, which can lead to the delamination of coatings. Geopolymer coating materials offer an environmentally friendly solution to this concern to encourage sustainable growth. The simplicity with which geopolymers can be synthesized and their low emission of greenhouse gases such as CO2, SO2, and NOx are advantages of geopolymers. The advent of geopolymer coatings with photocatalytic properties is advantageous for the decomposition of pollution and self-cleaning properties. The aim of this paper is to study the optimum solid-to-liquid ratio of metakaolin geopolymer paste added TiO2 and ZnO by adhesion strength. Through iterative mixture optimization, we investigated the effects of different design parameters on the performance of a metakaolin-based geopolymer as a coating material. The assessed material was a metakaolin which was activated by an alkali activator (a mixture of sodium hydroxide and sodium silicate), with the addition of titanium dioxide and zinc oxide as photocatalyst substances. Varying proportions of solid-to-liquid ratio were tested to optimize the best mix proportion related to the coating application. Adhesion analyses of geopolymer coating paste were evaluated after 7 days. According to the findings, the optimal parameters for metakaolin geopolymer coating material are 0.6 solid-to-liquid ratios with the highest adhesion strength (19 MPa) that is suitable as coating material and enhanced the properties of geopolymer

Electrical capacitance tomography: a review on portable ECT system and hardware design

Purpose – There are demands from the industry to have a modern application of Electrical Capacitance Tomography (ECT) system which is mobile and agile. One of the factors why such system is needed in the industry is because of the requirement to install the measurement sensors in a hostile and harsh environment which demands a special kind of ECT system. This paper will discuss the features of mobile or portable ECT which is more practical to be implemented in the harsh environment. Besides, the implementation of cloud computing and wireless technology in the portable ECT systems is also discussed. This review outlines some key features of portable or in another word mobile ECT as a complete system. Design/methodology/approach – There are demands from the industry to have a modern application of ECT system which is mobile and agile. One of the factors why such system is needed in the industry is due to the requirement to install the measurement sensors in hostile and harsh environment which demands a special kind of ECT systems. This paper will discuss the features of mobile or portable ECT which is more practical to be implemented in the harsh environment. Besides, the implementation of cloud computing and wireless technology in the portable ECT systems is also being discussed. This review outlines some key features of portable or in another word mobile ECT as a complete system. Findings – This review outlines some key features of portable or in another word mobile ECT as a complete system. A lot of improvement can be done to realize a reliable and stable ECT system. It is seems that in the near future, machine to machine communication will become the main stream. Originality/value – This paper fulfils an identified need to study improvement that can be done to develop a portable ECT system which is reliable and stable. Besides, the implementation of cloud computing and wireless technology in the portable ECT systems is also discussed