Volume volume 24 no.1 2016

In bone tissue engineering, porous calcium phosphate represents promising scaffolding materials to repair diseased or damaged bone tissue (Chen et al., 2008). However the main problem of these structures is due to its slow mechanical properties and high brittleness. The main focus of this work is to develop a scaffold using foam replication technique to produce highly porous, biodegradable and mechanically competent structures. In order to determine degradation rate, the scaffolds were immersed in Simulated Body Fluid (SBF) and Phosphate Buffer Saline (PBS). A polyurethane (PU) foam with a dimension of (20 x 10 x 20) mm was immersed in  a slurry mixture of apatite powder and poly vinyl alcohol (PVA),  which subsequently infiltrates into the porous structure while forming a homogeneous coating of calcium phosphate particles on the surface of the PU form. After drying, the green body was slowly burned off at sintering temperature of 1150 °C for 3 hours to obtain porous scaffolds, followed by dipping in PDLLA solution at 1, 3 and 5 wt/v.%  in order to improve mechanical stability, and dried at room temperature for 24 hours. The scaffolds were analysed under X-ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Universal Testing Machine (UTM). The X-ray diffraction (XRD) spectrum revealed the presence of sharp peaks of hydroxyapatite  (HA)[Ca₁₀(PO₄) ₆(OH)₂] phases before and after sintered scaffolds. SEM micrograph showed the structure of scaffold with highly porous and interconnected pores.The weight loss results indicated that calcium phosphate scaffold was degraded after 136 days in SBF and 142 days in PBS, respectively.

Generally, TiO₂ based materials that undergo thermal treatment can exist in three different crystalline phases which are rutile (tetragonal), anatase (tetragonal) and brookite (orthorombic). Rutile is the most stable form, whereas anatase and brookite are in metastable and readily transformed to rutile when heated. In order to investigate the effects of dopant in photocatalytic activities towards changes of temperature treatment, tungsten oxide, WO₃ was incorporated into TiO₂ structure at different thermal temperatures. The results indicated that tungsten oxide was found to contribute towards the formation of stabilized rounded nanoparticles structure and the XRD spectra indicated mixture of nanocrystals composite anatase-rutile at 600 °C. The WO₃-doped TiO₂ showed active photo-degradation in trans-cinnamic acid throughout 90 minutes of test duration. It exhibited better performance in decomposition of trans-cinnamic acid at 100 % within 90 minutes at 500 and 600 °C thermal treatment.

Tan Yong Nee, Abdul Hafiz Abd Malek, Mohamad Zahid Abdul Malek, Noor Zalikha Mohamed Islam, Shamsul Azrolsani Abdul Aziz Nazri,Mat Tamizi Zainuddin

This work focuses on designing bilayered constructs by combining a freeze-drying method and Bioglass^®-derived scaffolds (BG) for osteochondral tissue replacement materials. PDLLA (poly-D,L-lactic acid) layer of the constructs was fabricated using 7.5 wt/v% PDLLA in dimethyl carbonate for 3, 5 and 7 days freeze-drying duration. The PDLLA layer can be varied at least by 1 cm thickness. Mechanical strength and morphology of the bilayered constructs were characterised by Universal Testing Machine (UTM) and Scanning Electron Microscopy (SEM), respectively. In conclusion, the bilayered constructs developed by combining freezedrying and sintering method of Bioglass^®-based composite scaffolds have produced a well integrated interface combining both the bone structure and cartilage structure constructs. Bioactivity of the PDLLA layer showed that HA mineralisation decreased as the thickness of the PDLLA increased. In vitro studies suggested that PDLLA layer induced osteochondral cells proliferation.

Generally, there are two methods to form the BMS functions which are using discrete components and BMS ASIC. Current methods used discrete component for monitoring and balancing circuit which increase circuit complexity.  This leads to risk of short circuit that may cause battery damage and fire or explosion.  In addition, discrete components require more design effort and give low accuracy measurements compared to BMS ASIC.  Objective of this paper is to investigate BMS ASIC to fulfill the safety requirements of BMS.  The BMS ASIC can prevent the battery from operating outside its safe operating area. The BMS provide protection for overcurrent, overvoltage during charging, undervoltage during discharging and over temperature. Secondly,  to maximize the battery’s capacity by ensuring that the cells battery are kept at the same State of Charge (SOC) by wasting energy from the most charged cells through a dummy load through balancing.  Finally, the usage of BMS ASIC is in line with National Key Economic Areas (NKEAs) that to strengthen the Electronics and Electrical (E&E) capabilities by focusing in semiconductors technology.  To fulfill the objective, the BMS ASIC based on Linear Technology’s IC LTC6802-2 is used.  Two configuration namely as C and D were tested by using dummy load to replace LiFePO₄ battery.  Result obtained from both configuration shows that the LTC6802-2 IC can be used as BMS.

Piping are used for several applications, e.g., water and gas distribution to homes, chemicals, oil and gas supplies for different industrial applications, steam supply to steam turbines, etc. Early detection of defects (holes and/or blockage) due to scale deposit in such pipe is important so that it can be rectified in time. Nondestructive methods are inevitable within the multi-million industry to prevent losses, in both human and money. Much research has been done using the guided waves inspection techniques, more often by means of studying the ultra-sonic wave propagation characteristic within the solid isotropic structures with the needs to empty pipelines for such study. In this paper, an impulse wave is introduced at open end of a pipe and then the travel of the longitudinal wave within the pipe is studied. Multiple widths of half sine input pulse were analysed in a mathematical model and compared with experimental data. The paper presents the potential travelling distance and peak values using both analytical modelling and experimental results.

This paper presents the performance analysis of custom designed solar simulator. This work aims to cater the need for testing solar collector at National Metrology Institute of Malaysia (NMIM). The solar simulator was built using locally available material of supporting frame and halogen lamps as source of light. The analysis was carried out at four different irradiance intensities. To obtain the required irradiance intensity, the method used was by switching on certain numbers of the lamps while turning off the others. The uniformity of the irradiance was then evaluated by performing irradiance mapping measurement. This study has shown that the fabricated solar simulator was capable of producing irradiance intensity setting of ~ 400 W/m², ~ 600 W/m², ~ 700 W/m² and ~ 900 W/m². The solar simulator also managed to offer good repeatability of measurement with low non-uniformity that was within ± 5 % to ± 7 %.

Ceramic products consist of various types of ceramic bodies such as earthenware, stoneware, porcelain and bone china or synthetic bone china. Bone china and synthetic bone china are the most impressive because of their excellent whiteness, strength and translucency. The anorthite-based ceramic body which is equivalent to synthetic bone china or e-bone with respect to their whiteness and translucency, also has a lower thermal expansion coefficient (TEC) of about  5.20 x 10-6/K. The anorthite-based ceramic body was produced by using the synthetic ash as a major component with addition of other clays. The synthetic ash was produced by calcining calcium carbonate, silica and aluminum trihydroxide as the starting materials. It contains anorthite as the major phase and corundum and quartz as the minor phases. The anorthite-based ceramic body has difficulty to suit with the ordinary glaze. Cracking and crazing problem caused by strain effect due to the TEC mismatch of the glaze and the body are common. A low TEC glaze of less than  5.20 x 10-6/K is being developed to suit the anorthite-based ceramics body by introducing low TEC glaze materials. More than sixty (60) glaze formulations including those using low TEC materials such as petalite, spodumen and lithium carbonate were studied. Three (3) petalite-based glaze formulas have shown promising results where their TEC values matched that of the body, with smooth and shining surface without crazing. Majority of the lower TEC glazes tend to have high firing temperature with matt surface. The properties of the low TEC glazes are described in this study.