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This research studies the strategy of risk evaluation of China government bonds with the latest data. The angle of evaluation focuses on the interest rate and the stability risk, employing the EWMAVaR and SVM methods. The weights of each risk indicator are determined by the entropy method. Experimental results show that the risk of government bonds is stable in recent years. However, the impact of COVID-19 cannot be ignored because the risk level increased in the year 2020. The issuing of one trillion special antipandemic bonds could explain the fluctuation of the market because the fiscal incomes of Chinese government decreased in 2020 and could not be recovered in a short time. The experimental results show that the method proposed in this paper has a better performance than the existing methods, and it can help well in realizing the risk assessment of government bonds.

It is a difficult time for the world’s economics while the impact of COVID-19 is undergoing. A possible worldwide sovereign debt crisis could emerge, in short term, for supply chains blockage due to its slowing-down in many countries. China, having the second largest economy in the world, is crucial for the stability and sustainability of the economic recovery. China endures a long-term growth since 2000; nevertheless, a large amount of that growth is contributed by the government debt, which was spent on infrastructures. The accumulation of debts is a potential risk to the future growth of China. This research evaluates the central government and local government debts with a series of indicators. The weights of indicators are determined by objective methods of the CRITIC approach. Results confirm that the central government debt of China is on the edge of risk, while the risk of local governments debt is already in a concerning danger. The local government risk is 50% higher than the central government’s risk. Moreover, the K-means clustering algorithm performed on data, collected from various provinces, suggests that the local government debts of China follow a pattern of geographical distribution; that is, the closer to the coast, the lesser the risk, which is in accordance with the pattern of labor flowing. Labors are attracted by job opportunities which lie in the well-developed regions of China. This is confirmed by the crosscheck with the wage growth data. This indicates that the less developed areas of China rely more heavily on debt-investment stimulation that could be of a potential stagnation because the yield of investment follows diminishing marginal returns and the relative lacking labor weakens the potential economic growth.

We report a facile fabrication method for copper nanoparticle superlattices, based on thermal evaporation of ultrathin layers of copper on solution-processed thin films formed by few-layer graphene platelets. We show that the annealing of these systems in nitrogen without previous exposure to air prompts the heterogeneous nucleation of the Cu layer into nanoparticle superlattices self-assembled along specific crystallographic directions of graphene. Theoretical calculations suggest a lowest formation energy for Cu-nanoparticle arrays aligning along armchair directions, indicating that their self-assembly is energetically more favourable. The possibility of using these superlattices in evanescent waveguiding devices is explored by three-dimensional scanning near-field optical microscopy. The light-confining properties of our systems in the near-field indicate that our nanoparticle superlattices are poised to satisfy the technological demands required by nanophotonics devices.