The selective functionalization of graphene edges is driven by the chemical reactivity of its carbon atoms. The chemical reactivity of an edge, as an interruption of the honeycomb lattice of graphene, differs from the relative inertness of the basal plane. In fact, the unsaturation of the pz orbitals and the break of the π conjugation on an edge increase the energy of the electrons at the edge sites, leading to specific chemical reactivity and electronic properties. Given the relevance of the chemistry at the edges in many aspects of graphene, the present Review investigates the processes and mechanisms that drive the chemical functionalization of graphene at the edges. Emphasis is given to the selective chemical functionalization of graphene edges from theoretical and experimental perspectives, with a particular focus on the characterization tools available to investigate the chemistry of graphene at the edge.
One of the sources of instability in pumps is cavitation phenomenon. Cavitation in a pump can cause some undesirable effects, such as deterioration of the hydraulic performance (drop in head-capacity and efficiency curves), damage of the pump by pitting and erosion, structure vibration and resulting noise. Cavitation can appear within the entire range of operating conditions; therefore its occurrence inside a pump and its intensity must, by all means, be identified. In the present study, alternations in the velocity of an axial flow pump structure, for the first time used to investigate Cavitation. An average energy method for identification cavitation occurrence and measurement its intensity has been developed. This is called the Logarithmic Cavitation Intensity (LCI). To establish the pump cavitation conditions, a statistical analysis has been undertaken in a real-time and an LCI has been recommended as a proper criterion for defining the cavitation intensity. The results also showed the proposed method besides some other advantages comparing other detection methods, is feasible by simple hardware with low sampling frequency resulting in reducing the computational time as well as hardware complexity and cost.
2D motion pattern of an especial type of sand, which is used in lost-foam casting process, under the horizontal vibration investigated. Under this condition, the sand bulk in the experiment cell divides into 3 different zones, every one has its own property. Using dimensional analysis for the first time for this problem, dimensionless parameters which are useful to study sand bulk behavior, were identified. It observed that simple and linear relations exist among these parameters. They can be utilized in formulizing this phenomenon, by which motion pattern of sand bulk in various conditions can be predicted and optimum of geometric and vibration parameters for different purposes can be identified. The results not only are useful for this type of sand, but also may be extended to other types of granular materials too. The used method for detection what goes in the cell, without utilizing any external probe which may change the real conditions of the experiment cell, is another innovation of this study.
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