Mitigating Interference in a Heterogeneous Wireless Network using Channel Selection

 
With the extensive development of heterogeneous wireless communication technology, combined with the advances of data acquisition, emerges a new trend of networked acquisition systems. Among this range of wireless technology, Wireless Sensor Networks (WSNs) has attracted much interest and visibility due to its huge application space. One challenge using the WSN is the short range of the sensor nodes that increases the complexity of transporting the data to a central server. The integration with Wireless Mesh Networks (WMNs) expands the communication range and allows mobility of the device. Thus, WSN can be used for forming the underlying sensing and WMN supports the network infrastructure in pervasive computing environments. However, interference is a problem as these networks share the same 2.4GHz industrial, scientific and medical (ISM) unlicensed band. The impact of the interference on the IEEE 802.11g (WMN) using OFDM modulation and on IEEE 802.15.4 (WSN) using DSSS is investigated in this research. Results from a series of experiments on the AIT wireless mesh campus network under realistic load conditions are presented. Packet retransmission and packets drop rate were measured and based on this knowledge, a channel interference classification (CIC) method is presented to identify the interfering operating channel. The method introduced is based on a technique proposed by Chowdhury et. al. for channel selection based on reference power values. This work modifies the technique to account for differences on channel spectrum characteristic found in tests on the Mesh Campus Network. A channel selection algorithm was then developed for WSN to decide on the operating transmission channel that is not under interference, hence reducing packet losses in the network. This paper will be of interest to network operators and organisations where critical information retrieval over wide area networks is required.

Keywords: Wireless sensor networks (WSNs), IEEE 802.15.4, channel interference, wireless network coexistence.

Studies of Geopolymerization Route For Metakaolin Geopolymeric Materials

 
Investigation on production of metakaolin geopolymeric powder was aimed to increase the productivity and application of geopolymer products. Geopolymerization process was applied in the manufacturing of metakaolin geopolymeric powder to be used in geopolymer synthesis. Geopolymer slurry was made by alkaline activation of metakaolin in alkali activator solution (a mixture of NaOH and sodium silicate solutions). The geopolymer slurry was heated in an oven to produce pre-cured paste and then pulverized to get uniform particle size geopolymeric powder. By adopting the concept of “just add water”, the metakaolin geopolymeric powder was mixed with water and then oven-cured to produce resulting geopolymer pastes. The results showed that the optimum conditions for producing highest strength resulting paste are by using 8M of NaOH solution, solids/liquid ratio of 0.80, an activator ratio of 0.20, pre-curing of 80°C for 4 hours, 22% of mixing water and curing regime of 60°C for 72 hours. The resulting geopolymer pastes have low bulk density and were potential for a lightweight material. Upon the mixing of water with geopolymeric powder, densification of the structure occurred with the formation of compact geopolymer gels. The geopolymeric powder and resulting pastes showed the combination of amorphous and crystalline phases as analyzed by XRD. After ageing, the intensities of zeolites crystalline phases increased and this emphasized the benefit of zeolites in strength development of resulting pastes. This study clearly demonstrates that the production of metakaolin geopolymeric powder was able to be used in manufacturing geopolymer pastes.

Keywords: Geopolymer, powder, activator solution, geopolymerization, water

Polymer Nanocomposites for Piping Application

Epoxy based nanocomposites incorporating nanoclay and several types of geopolymer raw materials obtained from Saudi Arabia were explored for piping application. The flexural and compressive properties and performance were studied from several series of epoxy nanocomposites containing different ratio of epoxy/hardener, and nanoclay/geopolymer. In addition, different kinds of geopolymer raw materials such as fly ash, kaolin, pozzolonic, silica sand and white clay were employed as filler. The effect of different combination and ratio of these materials on the mechanical properties and morphology of the resulted nanocomposites were investigated. Preliminary studies showed promising properties of these nanocomposites for further development in pipe application.

Keywords:Polymer, Nanocomposite, Nanoclay, Geopolymer, Pipe, compressive strength, flexural strength, flexural modulus.

Advanced Anaerobic Suspended Growth Closed Bioreactor (ASGCB) for the Production of Biomethane Gas

Keywords: Anaerobic Degradation Process, Palm Oil Mill Effluent, Biogas Production, Methane Gas, Renewable Energy, Volatile Fatty Acids, 16S rDNA Bacterial Identification.