A method to reach the globular weld structure of A356 aluminum alloy using stirring the localized semisolid zone during butt-joining is developed.Since the heat conductivity of this alloy is very high, the accurate co...A method to reach the globular weld structure of A356 aluminum alloy using stirring the localized semisolid zone during butt-joining is developed.Since the heat conductivity of this alloy is very high, the accurate controlling of temperature during joining must be considered.A gas heating system was used to heat up the nitrogen gas up to the required temperature.A dried and free oxygen gas was prepared when a stream of nitrogen gas could pass closely around a hot element.Hot and pure nitrogen gas flow through a precise ceramic nozzle was used to create a localized semisolid pool.At this stage a fine stirrer was introduced into the weld seam in order to mix the two sides into a single uniform joint.Substrates were moved in direction of joint line by a small trolley to avoid the deviation of nozzle from the joint line and its distance and angle from the substrate.A fixture system was used to hold two substrates together on the trolley.A narrow hot plate was located on the trolley to heat up the joint line due to high heat conductivity of aluminum.Effect of gas temperature was investigated on the microstructure and mechanical properties of weld seam.Results showed that increase in temperature promoted the final welding properties, and also at liquid fractions less than 50% joining was not fully practical.The best mechanical properties were achieved with liquid fraction of about 70%.展开更多
The use of the multimodel approach in the modelling, analysis and control of non-linear complex and/or ill-defined systems was advocated by many researchers. This approach supposes the definition of a set of local mod...The use of the multimodel approach in the modelling, analysis and control of non-linear complex and/or ill-defined systems was advocated by many researchers. This approach supposes the definition of a set of local models valid in a given region or domain. Different strategies exist in the literature and are generally based on a partitioning of the non-linear system’s full range of operation into multiple smaller operating regimes each of which is associated with a locally valid model or controller. However, most of these strategies, which suppose the determination of these local models as well as their validity domain, remain arbitrary and are generally fixed thanks to a certain a priori knowledge of the system whatever its order. Recently, we have proposed a new approach to derive a multimodel basis which allows us to limit the number of models in the basis to almost four models. Meanwhile, the transition problem between the different models, which may use either a simple commutation or a fusion technique, remains still arise. In this plenary talk, a fuzzy fusion technique is presented and has the following main advantages: （1） use of a fuzzy partitioning in order to determine the validity of each model which enhances the robustness of the solution; 2 introduction, besides the four extreme models, of another model, called average model, determined as an average of the boundary models.展开更多
The increase of waste production, joined to the difficulties concerning both the identification of new disposal sites and the construction of big conventional incinerators, led in recent years to the development of ne...The increase of waste production, joined to the difficulties concerning both the identification of new disposal sites and the construction of big conventional incinerators, led in recent years to the development of new technologies for waste management such as gasification and melting treatments. The possibility to introduce in the Italian context the DMS （direct melting system） technology, designed and manufactured by Nippon Steel Engineering Co. Ltd., has been taken into account for the scope of proposed work. DMS technology consists in MSW gasification, slags melting and combustion of the syngas produced, with the consequent generation of electric energy through a steam cycle. The system minimizes environmental impact, thanks to an effective recycling of useful resources such as inert melted slags and metals, featuring high flexibility in terms of treatment capacity due to its modular design. The aim of this article is to consider different plant configurations in order to optimize the energy recovery downstream the DMS module. As a case study, landfill gas exploitation integrated in the DMS plant will be considered as a typical situation that could occur in the Italian scenario. The energetic input provided by the biogas allows improving the thermo-economic performances according to market incentives.展开更多
文摘A method to reach the globular weld structure of A356 aluminum alloy using stirring the localized semisolid zone during butt-joining is developed.Since the heat conductivity of this alloy is very high, the accurate controlling of temperature during joining must be considered.A gas heating system was used to heat up the nitrogen gas up to the required temperature.A dried and free oxygen gas was prepared when a stream of nitrogen gas could pass closely around a hot element.Hot and pure nitrogen gas flow through a precise ceramic nozzle was used to create a localized semisolid pool.At this stage a fine stirrer was introduced into the weld seam in order to mix the two sides into a single uniform joint.Substrates were moved in direction of joint line by a small trolley to avoid the deviation of nozzle from the joint line and its distance and angle from the substrate.A fixture system was used to hold two substrates together on the trolley.A narrow hot plate was located on the trolley to heat up the joint line due to high heat conductivity of aluminum.Effect of gas temperature was investigated on the microstructure and mechanical properties of weld seam.Results showed that increase in temperature promoted the final welding properties, and also at liquid fractions less than 50% joining was not fully practical.The best mechanical properties were achieved with liquid fraction of about 70%.
文摘The use of the multimodel approach in the modelling, analysis and control of non-linear complex and/or ill-defined systems was advocated by many researchers. This approach supposes the definition of a set of local models valid in a given region or domain. Different strategies exist in the literature and are generally based on a partitioning of the non-linear system’s full range of operation into multiple smaller operating regimes each of which is associated with a locally valid model or controller. However, most of these strategies, which suppose the determination of these local models as well as their validity domain, remain arbitrary and are generally fixed thanks to a certain a priori knowledge of the system whatever its order. Recently, we have proposed a new approach to derive a multimodel basis which allows us to limit the number of models in the basis to almost four models. Meanwhile, the transition problem between the different models, which may use either a simple commutation or a fusion technique, remains still arise. In this plenary talk, a fuzzy fusion technique is presented and has the following main advantages: （1） use of a fuzzy partitioning in order to determine the validity of each model which enhances the robustness of the solution; 2 introduction, besides the four extreme models, of another model, called average model, determined as an average of the boundary models.
文摘The increase of waste production, joined to the difficulties concerning both the identification of new disposal sites and the construction of big conventional incinerators, led in recent years to the development of new technologies for waste management such as gasification and melting treatments. The possibility to introduce in the Italian context the DMS （direct melting system） technology, designed and manufactured by Nippon Steel Engineering Co. Ltd., has been taken into account for the scope of proposed work. DMS technology consists in MSW gasification, slags melting and combustion of the syngas produced, with the consequent generation of electric energy through a steam cycle. The system minimizes environmental impact, thanks to an effective recycling of useful resources such as inert melted slags and metals, featuring high flexibility in terms of treatment capacity due to its modular design. The aim of this article is to consider different plant configurations in order to optimize the energy recovery downstream the DMS module. As a case study, landfill gas exploitation integrated in the DMS plant will be considered as a typical situation that could occur in the Italian scenario. The energetic input provided by the biogas allows improving the thermo-economic performances according to market incentives.
