Applied Mechanics and Materials Vol. 815

Abstract: Large quantity of graphene oxide (GO) was prepared by Modified Hummer’s method, in which graphite was treated with a mixture of sulphuric acid, potassium permanganate and hydrogen peroxide. A chemically reduced graphene oxide (r-GO) was prepared using sodium borohydride (NaBH₄), followed by thermal treatment and thermal treatment of chemically reduce using NaBH₄. The electrical resistance of r-GO was measured using Keithley sourcemeter. The results revealed that r-GO show lower resistance on thermal reduction which is 2.39 kΩ compared to chemical reduction and thermal of NaBH₄ reduction which is 2.18 MΩ and 3.16 kΩ respectively. It can be concluded that thermal reduction is the best method to produce high conductivity r-GO film.

Abstract: This paper proposes the correlation of absorbed energy with calculated energy using the power spectrum density (PSD) method. The total absorbed energy was obtained using the dial/encoder system may significantly vary depending on the strength and ductility of the material. In addition, according to ASTM E23, over 80% of absorbed energy is inaccurate and approximate. For this reason, we determined the energy collected from the dial/encoder Charpy impact test using the signal processing approach. Strain gauges were connected to the Charpy impact striker and the high frequency data acquisition system in order to capture the dynamic impact strain response. Specimens of an aluminium alloy of 6061-T6 and carbon steel 1050 with different velocities and thicknesses were used in the experiment. The specimens are prepared based on the ASTM E23. A collection of signal was converted from the time domain to the frequency domain by means of PSD method and the area under its plot was used to calculate strain energy. The comparison between energy absorbed during the experiment with PSD peak and the strain energy were performed using different materials, velocities and thicknesses. The total energy absorbed for both material with the PSD peak and the strain energy using the dial/encoder system can be linked by a power law equation with R² 96% and R² 94 %. Thus, the effects of the strain signal pattern and impact duration with different parameters were correlated with the PSD peak and the strain energy. This correlation using PSD can be used as an alternative for the charpy impact test and solve the problem of inaccurate absorbed energy.

Abstract: This paper investigate the radiation efficiency enhancement for a small square patch resonator with the integration of single layer circular split ring metasurface mirror (CSRMM) operating at 5.8 GHz using Transmission Line Matrix (TLM) method. The single layer CSRMM provide an appropriate reflection phase to act as a mirror and is able to enhance the resonator gain and efficiency. This work shows a linear phase response from 5.8 GHz to 5.9929 GHz that is sufficient for 50 Ω wireless communication system operation. A siginificant improvement of 0.391 to 0.741 dBi IEEE gain over the whole frequency range was demonstrated. The resonator has an initial radiation efficiency of 0.246 and incremented to 0.406 once CSRMM is inserted. The resonator small size configuration provides adequate space for mounting the mirror close to the resonator, making it more fitting for modern wireless devices.

Abstract: Keystroke dynamics is known to be able to recognise a person associated with their way of typing on a computer keyboard. It is a fea-sible and useful method as an additional component to safety measures for identity verification. Previous studies show how keystroke dynamics can help to improve the recognition systems. Users behaviour when typ-ing, illustrates individual characteristics behind the computer screen. In this paper, we propose to use this application or technology along with a keypad to determine the construction workers’ attitude during work-ing hours, whether they have been working within a reasonable time or otherwise. This could possibly be a way to monitor their validity period while working. Keywords: Biometrics, keystroke dynamics, pattern recognition, construction.

Abstract: International Thermonuclear Experimental Reactor (ITER) is build based on the ‘tokamak’ concept of magnetic confinement, in which the plasma is contained in a doughnut-shaped vacuum vessel which powered up by the fuel of a mixture of deuterium and tritium. The two isotopes of hydrogen are then heated to a certain temperatures in excess of 150 million °C, forming hot plasma. The Blanket Module (BM) is arranged around the plasma to provide thermal and nuclear shielding for the vacuum vessel (VV), magnets, and other external component. Therefore, it is important to determine parameter that would affect the development process of BM. Analysis is very important in the design process for the ITER BM as well as nearby components. So a finite element model was developed on the BM and the detail part of the BM was developed using computer aided design (CAD) software. The detail part was inserted into the VV and several simulations were performed to find out the stress distribution within the wall of the BM. The constraint condition was find out and evaluated. The result shows that the maximum shear stress is 539.97MPa which exceed the allowable value of 515MPa. The result shows some acceptable stress levels in most of the analysed geometry. The result obtained was used to further modify the BM design in the cases where limits are exceeded.

Abstract: This work focuses on three different edge variation modified on the same circular split ring (CSR) longest arm of metallo dielectric periodic structure and its corresponding electromagnetic bandgap (EBG) behaviour as an alternative step to suppress surface wave. Three variants of circular split ring were studied to fulfill the requirements: Normal edge, triangular tip and tapered tip. These structures were optimized using Eigenmode Solver (EmS) with Advanced Krylov Subspace (AKS) method for full wave dispersion diagram. Final results shows a stable and good EBG region achieved from this CSR specifically within the 5.9 to 6 GHz region. The normal tip CSR that has a stable and good bandgap exits from 5.9265 GHz to 5.9516 GHz in between mode 5 and 6. While the triangular tip CSR bandgap is from 6.0214 GHz to 6.0378 GHz and tapered tip is from 6.0214 GHz to 6.0378 GHz.

Abstract: Artificial fish swarm algorithm (AFSA) is a class of swarm intelligent optimization algorithm stimulated by the various social behaviors of fish in search of food. AFSA can search for global optimum through local optimum value search of each individual fish effectively based on simulating of fish-swarm behaviors such as searching, swarming, following and bulletin. This paper presents an overview of AFSA algorithm by describing the evolution of the algorithm along with all the improvements and its combinations with various algorithms and methods as well as its applications in solving industrial problems.

Abstract: This research discusses about the principles of lean manufacturing in furniture export industries. The aim of this research is to improve productivity by reducing waste which exists in the production floor. This research discusses about the implementation of Value Stream Mapping (VSM) as waste initial identification instrument, standardization work, and Single Minute Exchange of Die (SMED) as an analysis tool and improvement implementation. Both of that methods are conducted in this research. This research is practically applicable and proven to be able to reduce waste which exists in production floor and to improve the factory’s productivity.

Abstract: This paper describes an overview of Fuzzy Logic (FL) application for solving machining problems. The developed fuzzy prediction model is an essential operational guideline for machinist in decision making and adjusting process parameters. This paper also discussed the previous literature that applied the FL in modeling machining process.

Abstract: Recently, Firefly Algorithm (FA) has become an important technique to solve optimization problems. Various FA variants have been developed to suit various applications. In this paper, FA is used to optimize machining parameters such as % Volume fraction of SiC (V), cutting speed (S), feed rate (F), depth of cut (D) and machining time (T). The optimal machining cutting parameters estimated by FA that lead to a minimum surface roughness are validated using ANOVA test.