Since the discovery of graphene, many efforts have been done to modify the graphene structure for integrating this novel material to nanoelectronics, fuel cells, energy storage devices and in many other applications. ...Since the discovery of graphene, many efforts have been done to modify the graphene structure for integrating this novel material to nanoelectronics, fuel cells, energy storage devices and in many other applications. This leads to the production of different types of graphene-based materials, which possess properties different from those of pure graphene. Porous graphene is an example of this type of materials. It can be considered as a graphene sheet with some holes/pores within the atomic plane. Due to its spongy structure, porous graphene can have potential applications as membranes for molecular sieving, energy storage components and in nanoelectronics. In this review, we present the recent progress in the synthesis of porous graphene. The properties and the potential applications of this new material are also discussed.展开更多
The drying of grapes is a more complex process compared to the dehydration of other agricultural materials due to the necessity of a pretreatment operation prior to drying. Grape drying to produce raisins is a very sl...The drying of grapes is a more complex process compared to the dehydration of other agricultural materials due to the necessity of a pretreatment operation prior to drying. Grape drying to produce raisins is a very slow process, due to the peculiar structure of grape peel, that is covered by a waxy layer. Its removal has been so far carried out by using several chemical pre-treatments. However, they cause heterogeneity in the waxes removal and create microscopic cracks. In this paper an abrasive pretreatment for enhancing the drying rate and preserving the grape samples is proposed. Two cultivars of grape were investigated: Regina white grape and Red Globe red grape. The drying kinetics of untreated and treated samples were studied using a convective oven at 50°C. Fruit quality parameters such as sugar and organic acid contents, shrinkage, texture, peel damage (i.e. by SEM analysis) and rehydration capacity were studied to evaluate the effectiveness of abrasive pretreatment on raisins. Abrasive pretreatment contributed to reduce drying time and rehydration time. The treated and untreated dried grapes were significantly different (p < 0.05) in sugar and in tartaric acid content. On the contrary, no significant differences (p < 0.05) in malic and citric acids and in texture properties between untreated and treated samples were observed.展开更多
Modelling based on Computational Fluid Dynamics(CFD)is by now effectively used in fire research and hazard analysis.Depending on the scenario,radiative heat transfer can play a very important role in enclosure combust...Modelling based on Computational Fluid Dynamics(CFD)is by now effectively used in fire research and hazard analysis.Depending on the scenario,radiative heat transfer can play a very important role in enclosure combustion events such as tunnel fires.In this work,the importance of radiation and the effect of the use of different approaches to account for it were assessed.Firstly,small-scale tunnel fire simulations were performed and the results compared with experimental data,then realistic full-scale scenarios were simulated.The results show up the capability of CFD modelling to reproduce with good approximation tunnel fires.Radiation proved to be noteworthy mainly when the scale of the fire is relatively large.Among the various approaches employed to simulate radiation,the use of the Discrete Transfer model gave the most accurate results,mainly when the absorption-emission characteristics of the combustion products were taken into account.Finally,the suitability of the use of CFD in quantitative Fire Hazard Analysis is discussed.展开更多
基金partially supported by the Natural Science and Engineering Council of Canada (NSERC, Canada)the financial support from the high level overseas talent project of Beijing, P. R. China
文摘Since the discovery of graphene, many efforts have been done to modify the graphene structure for integrating this novel material to nanoelectronics, fuel cells, energy storage devices and in many other applications. This leads to the production of different types of graphene-based materials, which possess properties different from those of pure graphene. Porous graphene is an example of this type of materials. It can be considered as a graphene sheet with some holes/pores within the atomic plane. Due to its spongy structure, porous graphene can have potential applications as membranes for molecular sieving, energy storage components and in nanoelectronics. In this review, we present the recent progress in the synthesis of porous graphene. The properties and the potential applications of this new material are also discussed.
文摘The drying of grapes is a more complex process compared to the dehydration of other agricultural materials due to the necessity of a pretreatment operation prior to drying. Grape drying to produce raisins is a very slow process, due to the peculiar structure of grape peel, that is covered by a waxy layer. Its removal has been so far carried out by using several chemical pre-treatments. However, they cause heterogeneity in the waxes removal and create microscopic cracks. In this paper an abrasive pretreatment for enhancing the drying rate and preserving the grape samples is proposed. Two cultivars of grape were investigated: Regina white grape and Red Globe red grape. The drying kinetics of untreated and treated samples were studied using a convective oven at 50°C. Fruit quality parameters such as sugar and organic acid contents, shrinkage, texture, peel damage (i.e. by SEM analysis) and rehydration capacity were studied to evaluate the effectiveness of abrasive pretreatment on raisins. Abrasive pretreatment contributed to reduce drying time and rehydration time. The treated and untreated dried grapes were significantly different (p < 0.05) in sugar and in tartaric acid content. On the contrary, no significant differences (p < 0.05) in malic and citric acids and in texture properties between untreated and treated samples were observed.
文摘Modelling based on Computational Fluid Dynamics(CFD)is by now effectively used in fire research and hazard analysis.Depending on the scenario,radiative heat transfer can play a very important role in enclosure combustion events such as tunnel fires.In this work,the importance of radiation and the effect of the use of different approaches to account for it were assessed.Firstly,small-scale tunnel fire simulations were performed and the results compared with experimental data,then realistic full-scale scenarios were simulated.The results show up the capability of CFD modelling to reproduce with good approximation tunnel fires.Radiation proved to be noteworthy mainly when the scale of the fire is relatively large.Among the various approaches employed to simulate radiation,the use of the Discrete Transfer model gave the most accurate results,mainly when the absorption-emission characteristics of the combustion products were taken into account.Finally,the suitability of the use of CFD in quantitative Fire Hazard Analysis is discussed.
