Applied Mechanics and Materials Vol. 679

Abstract: Cross sectional areas optimization is to be implemented to study the influence of the cross section shape on the optimum truss weight. By the aid of analysis and design engines with advanced finite element analysis that is the steel design software STAAD. Four rolled steel sections (angle, tube, channel, and pipe) which are used in industrial roof trusses are applied for comparison. Many previous studies, use the areas of cross sections as design variables without highlight to the shape of cross section at the start of the process, consequently the result area will be adequate if the designer choose the effective shape than others. Results of this research show that the chosen cross section shape has a significant impact on the optimum truss weight for same geometry of truss type under the same circumstances of loading and supports.

Abstract: The argumentation of previous studies demonstrated the historical evolution of the materials in architecture and the position of the materials in the design process. The purpose is to recognize the role of materials in architectural design, and the materials are a core element of the design process. This paper is about the way materials can be used to create personality and character of the design. The research finds two overlapping roles for materials which are providing technical functionality and building personality. Thus building materials were one of the major factors for new innovation forms through the history of architecture. Keywords: Building Materials, Architectural Design, Technical Functionality, Aesthetic Attributes.

Abstract: This paper presents a 300W AC/DC/AC power converter for wind energy system. Magnetic Levitation Vertical Axis Wind Turbine is used to harness energy at low wind speed of less than 3 m/s which is suitable for residential area in Malaysia. Three phase voltage produces by wind turbine is rectified using three phase rectifier. A boost converter is employed to convert the rectified DC voltage to a higher level. The output stage consists of full bridge circuit that produces a sinusoidal AC voltage using SPWM switching technique for common AC loads. When operating in rated condition, this system reduces 300W of energy consumption from utility.

Abstract: This paper presents the mechanical properties of a lightweight geopolymer concrete synthesized by the alkali-activation of a fly ash source (FA) produced by mixing a paste of geopolymer with foam produced by using NCT Foam Generator. Two curing conditions are used, curing at room temperature and curing in an oven with a constant temperature which is 60 oC. Bulk density showed that fly ash-based geopolymer lightweight concrete is light with the density of 1225 kg/m³ - 1667 kg/m³ with an acceptable compressive strength of 17.60 MPa for the density of 1667 kg/m³.

Abstract: Currently, the application of diamond-like carbon (DLC) coatings for automotive components is becoming a favorable strategy to cope with the new challenges faced by the automotive industry. DLC coatings can effectively lower the coefficient of friction (CoF) and wear rate of engine components, consequently improving the fuel efficiency and durability of these components. Commercially available fully formulated lubricating oils enhance the lubrication of ferrous materials. Therefore, the interaction between nonferrous coatings (e.g., DLC) and commercial lubricating oil must be investigated. A ball-on-plate tribotester was used to run the experiments using stainless steel plates coated with tetrahedral DLC (ta-C) sliding against a 440C stainless steel ball. Wear track was investigated by scanning electron microscopy and atomic force microscopy. Energy dispersive spectroscopy was used to analyze the tribofilms inside the wear track. Raman analysis was performed to investigate the structural change of the coatings. At high temperatures, the CoF decreases but the wear rate increases in the ta-C DLC-coated plates. CoF and wear rate (coated layer and counter surface) are mostly influenced by coating graphitization.

Abstract: In this paper, we describe the improved performance of the SAC-OCDMA system using OFDM technique compared to SCM/SAC-OCDMA system. The theoretical results of proposed system shows that the new SAC/OCDMA system with OFDM technique provides better performance compared to SCM/OCDMA system based on multi diagonal code (MD), and the results have been evaluated based on BER and number of users for bit rate 1Gb/s and 10 Gb/s . Thus this system could be a promising solution to symmetric high capacity access networks with high spectral efficiency, cost effectiveness, good flexibility and enhanced security, which is candidate for next generation networks.

Abstract: CFD simulation of a tidal current turbine shroud was performed using Ansys FLUENT commercial code and comparison was made with experimental data. The simulation result obtained was in good agreement with the experimental data. The coefficient of velocity, C_v was in the range of approximately 1.2 to 1.4 for both simulation and experiment. The present study gave useful information on the viability of CFD simulation for the initial evaluation of shroud design performance.

Abstract: Lead metal proved to be toxic. Its lethal effect became eminent. Many developed countries have banned lead usage in various applications. Seeking alternative material to replace lead is a crucial goal. As density concerns, tungsten-brass composite is a good candidate for lead replacement. In this study the radiation shielding effects of tungsten-brass composites were evaluated. To attain this goal, four tungsten-brass sets were prepared. The tungsten (W) wt. % in these specimens was ranged from 50 to 80, the balance is brass. The specimens were sintered at 10500C in alumina tube furnace under protective environment. To evaluate the radiation shielding performance of these specimens, two gamma ray sources, ¹³⁷Cs and ⁶⁰Co were utilized. The photon energy levels for these sources were of o.662MeV and 1.25MeV respectively. The measurements were performed using gamma spectrometer contains NaI (Tl) detector. The anti-radiation performance of the tungsten-brass was correlated to that of lead under similar conditions. Vickers micro hardness, relative sintered density, micro structural characterisation and linear attenuation coefficient (μ) were carried out. Samples with the highest Weight percentage of W has the highest hardness value while the one with the lowest Weight percentage of W. The linear attenuation coefficients of the specimens were significantly improved by increasing the W wt. % of the specimen. The linear attenuation coefficients of the tested specimens ranged from 0.85±0.010cm^-1 to 1.12±0.049cm^-1for ⁶⁰Co and0.73±0.012 cm^-1 to 0.97±0.027 cm^-1 for ¹³⁷Cs. This result indicates that W-brass composites are suitable material for lead replacement as a shielding barrier.Keywords: Attenuation coefficient, radiation shielding, lead, tungsten-brass composites, NaI (Tl).

Abstract: Chloroform classified as one of the hazardous chemical to human. Therefore, monitoring the chloroform concentration in air is vital. In this study, chitosan powder was dissolved in 2% of acetic acid to form chitosan solution gel. It was subsequently deposited on printed circuit board (PCB) by using electrochemical deposition technique. The response of the chitosan sensor towards chloroform was tested via electrical testing by exposing different chloroform concentration ranging from 10 ppm, 20 ppm, 30 ppm, 40 ppm, and 50 ppm using air exposure technique. The response of the chitosan sensor towards chloroform was recorded as output voltage. Sensing properties of the chitosan sensor which include sensitivity, stability, recovery, and repeatability were studied. The electrical result showed that output voltage increases as the concentration of chloroform increases. All the sensing properties were achieved. The structure characterization of the chitosan was studied using Fourier Transform Infrared Spectroscopy (FTIR). The appearance of N-H and O-H groups in FTIR spectrum of chitosan film provides evidence that the domain functional group exist in chitosan after it was processed into film.