The last decade has seen an exponential rise in the use of wireless sensor networks (WSNs) in various applications. While these have been primarily used on their own, researchers are now looking into ways of integrating these WSNs with... more
The last decade has seen an exponential rise in the use of wireless sensor networks (WSNs) in various applications. While these have been primarily used on their own, researchers are now looking into ways of integrating these WSNs with other existing communication technologies. One such network is the satellite network which provides significant advantage in providing communication access to remote locations due to their inherent large coverage areas. Combining WSNs and satellite will enable us to perform efficient remotely monitoring in areas where terrestrial networks may not be present. However in such a scenario, the placement of sensor nodes is crucial in order to ensure efficient routing and energy-efficiency. This paper presents four network architectures for sensor-satellite hybrid networks; sensor-satellite direct communication, connections via a gateway node employing random node layout, grid-based node layout and cluster-based node layout with data aggregation. These architectures were simulated using network simulator 2 (ns-2) and then their packet loss rate, average end-to-end packet delay, and overall energy consumption were compared. The paper concludes by proposing a suitable network topology for environmental monitoring applications.
Recently there has been an exponential rise in the use of Wireless Sensor Networks (WSNs) in various applications. While WSNs have been primarily used as independent networks, researchers are now looking into ways of integrating them with... more
Recently there has been an exponential rise in the use of Wireless Sensor Networks (WSNs) in various applications. While WSNs have been primarily used as independent networks, researchers are now looking into ways of integrating them with other existing networks. One such network is the satellite network which provides a reliable communication backbone to remote areas that lack appropriate terrestrial infrastructure. However, due to the integration of the two networks with different transmission and operational characteristics interoperability and security become major concerns. This paper presents an ns-2 based simulation framework of a WSN-satellite integrated network that is used to evaluate the effects of data aggregation and security mechanisms on overall network performance. The average end-to-end packet delay, overall energy consumption and aggregation efficiency are considered for this analysis. This paper also looks into the effects of implementing hop-by-hop security and end-to-end security and justifies the need for end-to-end security in the WSN-satellite integrated networks.
In modern chemical plants, it is essential to establish an effective maintenance strategy which will deliver financially driven results at optimised conditions, that is, minimum cost and time, by means of a criticality review of equipment... more
In modern chemical plants, it is essential to establish an effective maintenance strategy which will deliver financially driven results at optimised conditions, that is, minimum cost and time, by means of a criticality review of equipment in maintenance. In this article, a fuzzy logic-based criticality assessment system (FCAS) for the management of a local company’s equipment maintenance is introduced. This fuzzy system is shown to improve the conventional crisp criticality assessment system (CCAS). Results from case studies show that not only can the fuzzy logic-based system do what the conventional crisp system does but also it can output more criticality classifications with an improved reliability and a greater number of different ratings that account for fuzziness and individual voice of the decision-makers.
Keywords: equipment criticality assessment; maintenance management; fuzzy system; group decision-making
To achieve a better solution of disc brake heat transfer problem under heavy duty applications, the accurate prediction of transient field of heat transfer coefficient is significant. Therefore, an appropriate coupling mechanism between... more
To achieve a better solution of disc brake heat transfer problem under heavy duty applications, the accurate prediction of transient field of heat transfer coefficient is significant. Therefore, an appropriate coupling mechanism between flow field and temperature field is important to be considered. In this paper, a transient conjugate heat transfer co-simulation disc brake model has been presented in order to improve the accuracy and feasibility of conventional coupled FE and CFD method. To illustrate the possible utilizations of this co-simulation method, a parameter study has been performed e.g. geometric, material, and braking application. The results show the advantage of the co-simulation method in terms of computing time efficiency and accuracy for solving complex braking heat transfer problem.
