Graphene is mainly implemented by these methods: exfoliating, unzipping of carbon nanotubes, chemical vapour deposition, epitaxial growth and the reduction of graphene oxide. The latter option has the advantage of low...Graphene is mainly implemented by these methods: exfoliating, unzipping of carbon nanotubes, chemical vapour deposition, epitaxial growth and the reduction of graphene oxide. The latter option has the advantage of low cost and precision. However, reduced graphene oxide(rGO) contains hydrogen and/or oxygen atoms hence the structure and properties of the rGO and intrinsic graphene are different. Considering the advantages of the implementation and utilization of rGO, voltage-dependent electronic transport properties of several rGO samples with various coverage ratios are investigated in this work. Ab initio simulations based on density functional theory combined with non-equilibrium Green's function formalism are used to obtain the current–voltage characteristics and the voltage-dependent transmission spectra of rGO samples. It is shown that the transport properties of rGO are strongly dependent on the coverage ratio. Obtained results indicate that some of the rGO samples have negative differential resistance characteristics while normally insulating rGO can behave as conducting beyond a certain threshold voltage. The reasons of the peculiar electronic transport behaviour of rGO samples are further investigated, taking the transmission eigenstates and their localization degree into consideration.The findings of this study are expected to be helpful for engineering the characteristics of rGO structures.展开更多
In this study low-concentration wastewater was investigated in the integral two-phase anaerobic baffled reactor by determining the removal of COD at various HRT,reflex ratios,and temperatures. Results indicate that th...In this study low-concentration wastewater was investigated in the integral two-phase anaerobic baffled reactor by determining the removal of COD at various HRT,reflex ratios,and temperatures. Results indicate that the removal efficiency of COD is more than 90% at 25 ℃ and 10-h HRT with no wastewater recycled,and the removal efficiency is up to 88% at 8-h HRT and reflex ratio of 150%. The removal efficiency is decreased with the decreasing temperature and HRT. The removal efficiency of COD is approximately 60% at 10 ℃,which proves that the temperature does not affect it apparently. This research has significance for reducing the cost of wastewater and sludge treatment in cold area.展开更多
With the proliferation of small and mini drones, Drone Small Cells(DSCs) can cooperative multiple drones to provide communication service for ground users as emergency means or supplementary ones of traditional terres...With the proliferation of small and mini drones, Drone Small Cells(DSCs) can cooperative multiple drones to provide communication service for ground users as emergency means or supplementary ones of traditional terrestrial cellular networks. In this paper, we study the fundamental problem of optimizing the deployment density of DSCs to achieve the maximum coverage performance. Most related works do not consider cumulative inter-cell interference when studying the coverage performance of DSCs. First, we derive an approximate and closed-form expression of the cumulative inter-cell interference which comes from both probabilistic Line-of-Sight(Lo S) and Non-Line-of-Sight(NLo S) links. Then, we analyze the coverage performance of DSCs and derive the transcendental function of optimal deployment density to obtain the maximum coverage. Last, we propose an algorithm to get the optimal deployment density with low complexity. We conduct both field experiments and Matlab simulations to verify the correctness of theoretical analysis. In addition, we show the impact of some factors on the relation between the deployment density and coverage performance through extensive numerical simulations.展开更多
文摘Graphene is mainly implemented by these methods: exfoliating, unzipping of carbon nanotubes, chemical vapour deposition, epitaxial growth and the reduction of graphene oxide. The latter option has the advantage of low cost and precision. However, reduced graphene oxide(rGO) contains hydrogen and/or oxygen atoms hence the structure and properties of the rGO and intrinsic graphene are different. Considering the advantages of the implementation and utilization of rGO, voltage-dependent electronic transport properties of several rGO samples with various coverage ratios are investigated in this work. Ab initio simulations based on density functional theory combined with non-equilibrium Green's function formalism are used to obtain the current–voltage characteristics and the voltage-dependent transmission spectra of rGO samples. It is shown that the transport properties of rGO are strongly dependent on the coverage ratio. Obtained results indicate that some of the rGO samples have negative differential resistance characteristics while normally insulating rGO can behave as conducting beyond a certain threshold voltage. The reasons of the peculiar electronic transport behaviour of rGO samples are further investigated, taking the transmission eigenstates and their localization degree into consideration.The findings of this study are expected to be helpful for engineering the characteristics of rGO structures.
基金Sponsored by the National Natural Science Foundation of China(Grant No. 50778080)China's Jilin Province Office of Education(Grant No.200696)Scientific Research Project of the Chinese Ministry of Education(Grant No.03034)
文摘In this study low-concentration wastewater was investigated in the integral two-phase anaerobic baffled reactor by determining the removal of COD at various HRT,reflex ratios,and temperatures. Results indicate that the removal efficiency of COD is more than 90% at 25 ℃ and 10-h HRT with no wastewater recycled,and the removal efficiency is up to 88% at 8-h HRT and reflex ratio of 150%. The removal efficiency is decreased with the decreasing temperature and HRT. The removal efficiency of COD is approximately 60% at 10 ℃,which proves that the temperature does not affect it apparently. This research has significance for reducing the cost of wastewater and sludge treatment in cold area.
基金supported in part by National NSF of China under Grant No.61472445,No.61631020,No.61702525 and No.61702545in part by the NSF of Jiangsu Province under Grant No.BK20140076.5
文摘With the proliferation of small and mini drones, Drone Small Cells(DSCs) can cooperative multiple drones to provide communication service for ground users as emergency means or supplementary ones of traditional terrestrial cellular networks. In this paper, we study the fundamental problem of optimizing the deployment density of DSCs to achieve the maximum coverage performance. Most related works do not consider cumulative inter-cell interference when studying the coverage performance of DSCs. First, we derive an approximate and closed-form expression of the cumulative inter-cell interference which comes from both probabilistic Line-of-Sight(Lo S) and Non-Line-of-Sight(NLo S) links. Then, we analyze the coverage performance of DSCs and derive the transcendental function of optimal deployment density to obtain the maximum coverage. Last, we propose an algorithm to get the optimal deployment density with low complexity. We conduct both field experiments and Matlab simulations to verify the correctness of theoretical analysis. In addition, we show the impact of some factors on the relation between the deployment density and coverage performance through extensive numerical simulations.
