Suchergebnisse

Social network has extended its popularity from the Internet to mobile domain. Pervasive social networking (PSN) supports instant social activities based on self-organized mobile ad hoc networks. PSN is useful in reality when fixed networks are unavailable or inconvenient to access or when people are in vicinity. For supporting crucial PSN activities and enhancing user privacy, securing pervasive social communications becomes important. However, a solution based on a centralized server could be inapplicable in some specific situations (e.g., disasters and military activities) and suffers from DoS/DDoS attacks and internal attacks. How to automatically control data access in a trustworthy and efficient way in PSN is a challenge. In this paper, we propose two schemes to secure communication data in PSN purely based on local trust evaluated by PSN nodes in a distributed manner. Each node can control its data based on its trust in other nodes by applying attribute-based encryption. The advantages, security, and performance of the proposed scheme are evaluated and justified through serious analysis and implementation. The results show the efficiency and effectiveness of the schemes. In addition, we developed a mobile app based on Android platform to demonstrate the applicability and social acceptance of our schemes. ; Peer reviewed

The Reactor Pressure Vessel (RPV) inlet nozzles and downcomer wall in Pressurized Water Reactors (PWR) may suffer serious thermal shock caused by cold water from reactor Safety Injection System (SIS) in some unexpected accident scenarios. It implies the formation of great temperature gradient on the inlet nozzles and RPV wall, leading to the localized stresses and propagation of possible flaws that appeared in the material. In this paper, the multiscale thermal hydraulic analysis was performed for Chashma Nuclear Power Plant (NPP) under the inadvertent SIS operation scenario. The primary loop and SIS were modeled using one-dimensional method, while the three-dimensional models of reactor cold leg, RPV inlet nozzles, and downcomer were established. Then, the inadvertent Safety Injection System operation scenario was simulated using RELAP5 code, providing the boundary conditions for three-dimensional Computational Fluid Dynamics (CFD) analysis. The fluid and solid coupling heat transfer simulation method was employed. Results show that the maximum temperature difference was about 80 K in the most conservative condition and the RPV inlet nozzle region was the most critical region during the accident. This work could provide in-depth understanding on the effect of cold coolant injection along the main pipes and RPV wall during the accident scenario.