A Review: Application and Implementation of Optic Fibre Sensors for Gas Detection

At the present time, there are major concerns regarding global warming and the possible catastrophic influence of greenhouse gases on climate change has spurred the research community to investigate and develop new gas-sensing methods and devices for remote and continuous sensing. Furthermore, there are a myriad of workplaces, such as petrochemical and pharmacological industries, where reliable remote gas tests are needed so that operatives have a safe working environment. The authors have concentrated their efforts on optical fibre sensing of gases, as we became aware of their increasing range of applications. Optical fibre gas sensors are capable of remote sensing, working in various environments, and have the potential to outperform conventional metal oxide semiconductor (MOS) gas sensors. Researchers are studying a number of configurations and mechanisms to detect specific gases and ways to enhance their performances. Evidence is growing that optical fibre gas sensors are superior in a number of ways, and are likely to replace MOS gas sensors in some application areas. All sensors use a transducer to produce chemical selectivity by means of an overlay coating material that yields a binding reaction. A number of different structural designs have been, and are, under investigation. Examples include tilted Bragg gratings and long period gratings embedded in optical fibres, as well as surface plasmon resonance and intra-cavity absorption. The authors believe that a review of optical fibre gas sensing is now timely and appropriate, as it will assist current researchers and encourage research into new photonic methods and techniques.

Open Access Broadband Networks in Alberta, Singapore, Australia and New Zealand

In policy debates about the appropriate regulation of next generation fibre access networks, a good deal of attention has been paid to various forms of ‘separation’ between network, wholesale and retail operations. This discussion is no longer theoretical, because ‘open access’ next generation networks are now operating or being constructed. This paper investigates four different models around the world, each at different stages of deployment: - Alberta, Canada, where a commercial company Axia has been operating the province-wide ‘SuperNet’ since 2005. This is an optic fibre network connecting 4700 sites (provincial government and municipality offices, health and education sites, libraries) in 27 urban and 402 rural communities. Axia is the government’s service provider across the whole network and the wholesaler of capacity to retail providers in the rural communities. - Singapore, where a network is under construction taking fibre to 1.12 million residential premises and 152,000 other premises. Separate companies are building the physical infrastructure (‘Net Co’) and installing the electronics and network termination devices in customer premises and operating the network (‘Op Co’). - Australia, where a national FTTP network is being built to reach 93% of households and businesses. Wireless will be used to deliver download speeds of at least 12 Mbps to the other 7%. Around 200,000 households will get FTTP in Tasmania, where services commenced in mid-2010. - New Zealand, where the national government has promised ‘superfast broadband’ within six years to all businesses, schools and health services, greenfields developments and some residential users, and to 75% of the population within ten years. Drawing on interviews conducted in the four territories in 2009 and 2010, the paper will investigate the common, contrasting and unique features of these four models.

Open Access Broadband Networks in Alberta, Singapore, Australia and New Zealand

In policy debates about the appropriate regulation of next generation fibre access networks, a good deal of attention has been paid to various forms of ‘separation’ between network, wholesale and retail operations. This discussion is no longer theoretical, because ‘open access’ next generation networks are now operating or being constructed. This paper investigates four different models around the world, each at different stages of deployment: - Alberta, Canada, where a commercial company Axia has been operating the province-wide ‘SuperNet’ since 2005. This is an optic fibre network connecting 4700 sites (provincial government and municipality offices, health and education sites, libraries) in 27 urban and 402 rural communities. Axia is the government’s service provider across the whole network and the wholesaler of capacity to retail providers in the rural communities. - Singapore, where a network is under construction taking fibre to 1.12 million residential premises and 152,000 other premises. Separate companies are building the physical infrastructure (‘Net Co’) and installing the electronics and network termination devices in customer premises and operating the network (‘Op Co’). - Australia, where a national FTTP network is being built to reach 93% of households and businesses. Wireless will be used to deliver download speeds of at least 12 Mbps to the other 7%. Around 200,000 households will get FTTP in Tasmania, where services commenced in mid-2010. - New Zealand, where the national government has promised ‘superfast broadband’ within six years to all businesses, schools and health services, greenfields developments and some residential users, and to 75% of the population within ten years. Drawing on interviews conducted in the four territories in 2009 and 2010, the paper will investigate the common, contrasting and unique features of these four models.

Interactions between energy geostructures in the same aquifer

<p>Energy geostructures are a very cost-effective geothermal solution to produce renewable energy for the heating and cooling needs of the buildings. Their principle is to attach heat exchange pipes to the reinforcing cages of geotechnical structures (foundations, retaining walls, …). Mechanical and thermal roles are assigned to the same structures in order to reduce the economic and ecological costs.</p><p>Perturbations of the temperature field induced in the soil by this technology are propagated through conduction, diffusion and advection along the water-flow, leading to thermo-hydro-mechanical interactions between neighbouring structures. The behaviour of downstream energy geostructures is affected by the presence of upstream ones. In order to achieve a smart management of the shallow geothermal development at the city scale, it is crucial to characterize these interactions and their influence on the thermal efficiency.</p><p>For this purpose, a group of nine energy piles has been studied in Sense-City, a mini city where a specific climate can be imposed and the underground water-flow can be controlled. The piles can be thermally activated separately and are equipped with optic fibre to monitor their temperature evolution through time. Different groundwater conditions were imposed and different combinations of activated piles were studied.</p><p>To extrapolate and upscale the results, a numerical model was developed with CESAR-LCPC, a FEM software. Challenged by the experimental observations, the numerical model allowed simulating more complex boundary conditions and thermal infrastructure configurations. Furthermore, numerical modelling are able to simulate a long term experiment and to predict potential multi-year thermal shift.</p><p>Using combination of experimental and numerical experiments, observations can be made on the positive or negative consequence of energy geostructures interactions.</p>