Ku Zilati Ku Shaari

Characterization of modified tapioca starch solutions and their sprays for high temperature coating applications.

The objective of the research was to understand and improve the unusual physical and atomization properties of the complexes/adhesives derived from the tapioca starch by addition of borate and urea. The characterization of physical properties of the synthesized adhesives was carried out by determining the effect of temperature, shear rate, and mass concentration of thickener/stabilizer on the complex viscosity, density, and surface tension. In later stage, phenomenological analyses of spray jet breakup of heated complexes were performed in still air. Using a high speed digital camera, the jet breakup dynamics were visualized as a function of the system input parameters. The further analysis of the grabbed images confirmed the strong influence of the input processing parameters on full cone spray patternation. It was also predicted that the heated starch adhesive solutions generate a dispersed spray pattern by utilizing the partial evaporation of the spraying medium. Below 40°C of heating temperature, the radial spray cone width and angle did not vary significantly with increasing Reynolds and Weber numbers at early injection phases leading to increased macroscopic spray propagation. The discharge coefficient, mean flow rate, and mean flow velocity were significantly influenced by the load pressure but less affected by the temperature.

Multiobjective Optimization of Green Sand Mould System Using Chaotic Differential Evolution

Many industrial optimization cases present themselves in a multi-objective (MO) setting (where each of the objectives portrays different aspects of the problem). Therefore, it is important for the decision-maker to have a solution set of options prior to selecting the best solution. In this work, the weighted sum scalarization approach is used in conjunction with three meta-heuristic algorithms; differential evolution (DE), chaotic differential evolution (CDE) and gravitational search algorithm (GSA). These methods are then used to generate the approximate Pareto frontier to the green sand mould system problem. The Hypervolume Indicator (HVI) is applied to gauge the capabilities of each algorithm in approximating the Pareto frontier. Some comparative studies were then carried out with the algorithms developed in this work and that from the previous work. Analysis on the performance as well as the quality of the solutions obtained by these algorithms is shown here.

Investigation of Vortex Clouds and Droplet Sizes in Heated Water Spray Patterns Generated by Axisymmetric Full Cone Nozzles

The hot water sprays are an important part of many industrial processes, where the detailed knowledge of physical phenomena involved in jet transportation, interaction, secondary breakup, evaporation, and coalescence of droplets is important to reach more efficient processes. The objective of the work was to study the water spray jet breakup dynamics, vortex cloud formation, and droplet size distribution under varying temperature and load pressure. Using a high speed camera, the spray patterns generated by axisymmetric full cone nozzles were visualized as a function water temperature and load pressure. The image analysis confirmed that the spray cone angle and width do not vary significantly with increasing Reynolds and Weber numbers at early injection phases leading to increased macroscopic spray propagation. The formation and decay of semitorus like vortex clouds were also noticed in spray structures generated at near water boiling point temperature. For the nozzle with smallest orifice diameter (1.19 mm), these vortex clouds were very clear at 90°C heating temperature and 1 bar water load pressure. In addition, the sauter mean diameter (SMD) of the spray droplets was also measured by using Phase Doppler Anemometry (PDA) at different locations downstream of the nozzle exit. It was noticed that SMD varies slightly w.r.t. position when measured at room temperature whereas at higher temperature values, it became almost constant at distance of 55 mm downstream of the nozzle exit.

Hopfield differential evolution for multi-objective optimization of a cement-bonded sand mould system

Frequently, optimization cases in engineering and other heavy industries present themselves in a multi-objective setting. Thus, it would greatly aid the decision maker if a series of multiple solutions were at hand prior to selecting the suitable solution. In this work, the weighted sum scalarization approach was used in conjunction with the Differential Evolution (DE) and the improved Hopfield Differential Evolution (Hopf-DE) algorithm. The DE and Hopf-DE approaches were then applied to the cement-bonded sand mould system to construct the approximate Pareto frontier, which was then employed to identify the best solution option. Some analysis was then performed on the computational results produced. Examination of the performance and the quality of the solutions obtained by the DE and Hopf-DE algorithms is presented. In addition, an analysis of the degree of conflict between the two objective functions with respect to the search space was carried out. The findings from this analysis are discussed in this paper.

An Algorithmic Framework for Multiobjective Optimization

Multiobjective (MO) optimization is an emerging field which is increasingly being encountered in many fields globally. Various metaheuristic techniques such as differential evolution (DE), genetic algorithm (GA), gravitational search algorithm (GSA), and particle swarm optimization (PSO) have been used in conjunction with scalarization techniques such as weighted sum approach and the normal-boundary intersection (NBI) method to solve MO problems. Nevertheless, many challenges still arise especially when dealing with problems with multiple objectives (especially in cases more than two). In addition, problems with extensive computational overhead emerge when dealing with hybrid algorithms. This paper discusses these issues by proposing an alternative framework that utilizes algorithmic concepts related to the problem structure for generating efficient and effective algorithms. This paper proposes a framework to generate new high-performance algorithms with minimal computational overhead for MO optimization.

Effect of pre-coat solution temperature on fluidized bed urea coatings

Abstract In this study, coating properties of the native cassava starch were improved by reacting it with urea and di-sodium tetraborate. The FTIR spectroscopy was used to study the possible reaction mechanism of the coating formulation. The prepared starch dispersions were used to coat 3·45 mm urea granules in a swirling fluidised bed reactor. An in-house built fluidised bed with an intermittent top spraying facility was used to coat the urea beds fluidised above their minimum level of fluidisation. The pre-coat solution temperature was varied from 50 to 80°C and the corresponding coated urea samples were further characterised for their surface morphology, coating hardness and nitrogen release time. The SEM images revealed that the surface of the coated urea was harder, denser and smoother as compared to the uncoated urea. Significant improvements in mechanical parameters of coated urea were seen with an increase in solution temperature and mass of the di-sodium tetraborate. The overall nutrients release time of the coated urea in water was increased from 63·33 to 209 s. The surface hardness and coating thickness of coated urea was also increased with an increase in pre-coat solution temperature and di-sodium tetraborate mass in the coating composition.

Visual Study of Hollow Cone Water Spray Jet Breakup Process at Elevated Temperatures and Pressures

The liquid jet breakup is a ubiquitous phenomenon in nature and a classic problem in hydrodynamics. The understanding of the jet breakup mechanism of hot liquids is still a challenge for researchers. The objective of this work was to understand and control the hot water spray jet breakup mechanism at moderate pumping pressures and elevated temperature. For this purpose, the visual and comparative studies were conducted on hollow cone water spray patterns generated by three hollow cone spray nozzles which were installed in an in-house built intermittently forced liquid spraying system. Using a high speed camera, the jet breakup dynamics were visualized as a function of system input parameters. The analysis of the grabbed images confirmed the strong influence of these processing parameters on spray characteristics. It was also predicted that heated liquids generate the dispersed spray patterns and the induction of thermal energy into the system enhances the jet disintegration ability. The spray cone width and angle were not varied significantly whereas the Weber and Reynolds numbers along with other spray parameters showed an appreciable response to the load pressure and water heating temperature at early stages of water injection.

Estimating young’s modulus of single-walled zirconia nanotubes using nonlinear finite element modeling

The single-walled zirconia nanotube is structurally modeled and its Youngs modulus is valued by using the finite element approach. The nanotube was assumed to be a frame-like structure with bonds between atoms regarded as beam elements. The properties of the beam required for input into the finite element analysis were computed by connecting energy equivalence between molecular and continuum mechanics. Simulation was conducted by applying axial tensile strain on one end of the nanotube while the other end was fixed and the corresponding reaction force recorded to compute Youngs modulus. It was found out that Youngs modulus of zirconia nanotubes is significantly affected by some geometrical parameters such as chirality, diameter, thickness, and length. The obtained values of Youngs modulus for a certain range of diameters are in agreement with what was obtained in the few experiments that have been conducted so far. This study was conducted on the cubic phase of zirconia having armchair and zigzag configuration. The optimal diameter and thickness were obtained, which will assist in designing and fabricating bulk nanostructured components containing zirconia nanotubes for various applications.

Hypervolume-Driven Analytical Programming for Solar-Powered Irrigation System Optimization

In the field of alternative energy and sustainability, optimization type problems are regularly encountered. In this paper, the Hypervolume-driven Analytical Programming (Hyp-AP) approaches were developed. This method was then applied to the multiobjective (MO) design optimization of a real-world photovoltaic (PV)-based solar powered irrigation system. This problem was multivariate, nonlinear and multiobjective. The Hyp-AP method was used to construct the approximate Pareto frontier as well as to identify the best solution option. Some comparative analysis was performed on the proposed method and the approach used in previous work.

Influence of Citric Acid and Curing Time on Water Uptake

Starch is highly promising biopolymer for the production of packaging material since it gives films a good tensile and gas barrier properties. However, non-plasticized starch films are brittle and their hydrophilic character results in poor moisture barrier properties and high water sensitivity. In order to improve films formation and material properties of starch, plasticization and chemical modification such as cross-linking of the starch is required. The cross-linking reaction able to improve thermal stability, tensile strength and decreased the dissolution of starch films in water and formic acid. From the study, the percentage of water uptake reduced when the blending ratio of citric acid increased.The percentage of water uptake highly affected by curing time compared to blending ratio. Increasing the curing time from 1 hour to 2 hour significantly reduced the percentage of water uptake. At 4 hour curing time, the percentage water uptake reached equilibrium faster than 3 hour curing time. This shows that more citric acid molecules were chemically bonded with the starch chains, resulting in higher cross link degree and thus, reduced the percentage of water uptake.