Transition-metal-embedded carbon nanotubes (CNTs) have been accepted as a novel type of sensing material due to the combined advantage of the transition metal, which possesses good catalytic behavior for gas interaction, and CNTs, with large effective surface areas that present good adsorption ability towards gas molecules. In this work, we simulate the adsorption of O2 and O3 onto Rh-doped CNT in an effort to understand the adsorbing behavior of such a surface. Results indicate that the proposed material presents good adsorbing ability and capacities for these two gases, especially O3 molecules, as a result of the relatively large conductivity changes. The frontier molecular orbital theory reveals that the conductivity of Rh-CNT would undergo a decrease after the adsorption of two such oxidizing gases due to the lower electron activity and density of this media. Our calculations are meaningful as they can supply experimentalists with potential sensing material prospects with which to exploit chemical sensors.

Carbon chain inserted carbon nanotubes (CNTs) have been experimentally proven having undergone pronounced property change in terms of electrical conductivity compared with pure CNTs. This paper simulates the geometry of carbon chain inserted CNTs and analyzes the mechanism for conductivity change after insertion of carbon chain. The geometric simulation of Pt doped CNT was also implemented for comparison with the inserted one. The results indicate that both modification by Pt atom on the surface of CNT and addition of carbon chain in the channel of the tube are effective methods for transforming the electrical properties of the CNT, leading to the redistribution of electron and thereby causing the conductivity change in obtained configurations. All the calculations were obtained based on density functional theory method.

It has been well acknowledged that Vessel Traffic Services (VTS) has played a growing important role to ensure the safety of navigation in the busy ports and waterways. However, the benefits produced by VTS are usually ignored by the public and private sectors. Besides, the previous evaluations generally exist following problems: (1) It is difficult to collect the data for the parameters in the evaluation models and/or the parameters are designed illogically; (2) Those models did not take the following factors into consideration such as reducing the frequency of coastal vessel patrolling and saving human and material resources; (3) It is difficult to clearly discriminate the benefits derived from VTS and non-VTS. In this paper, a framework is presented to calculate the benefits of VTS in China. Four key indicators (safety, traffic efficiency, environmental protection and reducing supervising cost) and quantitative methods have been introduced into the framework. When calculating the benefits quantitatively, the traffic condition before the construction (expansion) of the VTS has acted as a benchmark. For a case study, the project of the expansion of VTS in Zhoushan Port, East China was evaluated with 10-year data. According to the results, the largest contribution is from the benefit of environmental protection. Via Cost-benefit analysis the benefit cost ratio (B/C) of the VTS is up to 5.248, which shows the benefits produced by VTS are considerable. The research could provide references for VTS benefits evaluation and investment optimizing.

Since the 1990s, the influencing factors of enterprise entry and exit decisions have been explained from the perspective of fixed cost or sunk cost. And the concept of trade relationship duration of products or enterprises did not appear until 2006. Given its great significance for the steady growth of export trade, most of the literatures begin to analyze the duration of trade relations of countries in survival. This paper sorts out and evaluates the research content, method and conclusion, and obtains many valuable conclusions and enlightenment on this basis, and finally prospects the future research direction.