No abstract

The communication systems in existing smart grids mainly take the request/reply interaction model, in which data access is under the direct control of data producers. This tightly controlled interaction model is not scalable to support complex interactions among smart grid services. On the contrary, the publish/subscribe system features a loose coupling communication infrastructure and allows indirect, anonymous and multicast interactions among smart grid services. The publish/subscribe system can thus support scalable and flexible collaboration among smart grid services. However, the access is not under the direct control of data producers, it might not be easy to implement an access control scheme for a publish/subscribe system. In this article, we propose a Data-Centric Access Control Framework (DCACF) to support secure access control in a publish/subscribe model. This framework helps to build scalable smart grid services, while keeping features of service interactions and data confidentiality at the same time. The data published in our DCACF is encrypted with a fully homomorphic encryption scheme, which allows in-grid homomorphic aggregation of the encrypted data. The encrypted data is accompanied by bloom-filter encoded control policies and access credentials to enable indirect access control. We have analyzed the correctness and security of our DCACF and evaluated its performance in a distributed environment.

With the popularization of higher education and the promotion of college enrollment expansion, the number of college graduates increases sharply. At the same time, the continuous transformation and upgrading of the industrial structure put forward higher requirements on the employability of college students, which leads to the imbalance between supply and demand in the labor market. The key to dealing with employment difficulties lie in the improvement of college students’ employability. Therefore, we make a regression analysis of 263 valid samples from universities in Anhui Province and extract the factors that influence the improvement of college students’ employability in the process of talent cultivation in university. The result shows that there is a positive correlation between course setting, course teaching, club activities, and college students’ employability, among which the course teaching and club activities are the most critical factors which may influence college students’ employability. In addition, from the viewpoint of individual college students, the overall grades of college students and the time of participating in the internship are also closely related to their employability, i.e., college students with good overall grades and long internship time should also have stronger employability.

An inverse direct time domain boundary element method (IDTBEM) is proposed for the reconstruction of transient acoustic field radiated by arbitrarily shaped sources. The method is based on the theory of direct time domain boundary element method (DTBEM), which is free from the calculation of hypersingular integrals, and thus, its reconstruction process is relatively simple and easy to implement. However, the formulations of DTBEM cannot be used directly for the reconstruction of transient acoustic field, and therefore, new formulations with a modified time axis are derived. With these new formulations, a linear system of equations is formed and the reconstruction is performed in a marching-on-time (MOT) way. Meanwhile, to deal with the ill-posedness involved in the inverse process, the truncated singular value decomposition (TSVD) is employed. Numerical simulations with three examples of a sphere, a cylinder, and a simplified car model are carried out to verify the validity of IDTBEM, and the results demonstrate that the IDTBEM is effective in reconstructing the transient acoustic fields radiated by arbitrarily shaped sources in both time and space domains.