Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), power density and anode potential are used to characterize the mediator microbial fuel cell at different methylene blue (MB) concentrations. At lower MB concentration between 9.98×10-3 mmol/L and 1.66×10-1 mmol/L, the increased power density is enabled by using high mediator concentrations. Higher peak power density of 159.6 mw/m2 is observed compared with the peak power density of 36.0 mw/m2. But MB at too high concentration is disadvantageous to the perform of MFC. At the MB concentration of 2.50×10-1 mmol/L, the peak power output is just 128.4 mw/m2, which is lower than 159.6 mw/m2 at MB concentration of 1.66×10-1 mmol/L.

Information security is a great challenge for organizations in our modern information world. Existing security facilities like Firewalls, Intrusion Detection Systems and Antivirus are not enough to guarantee the security of information. File is an important carrier of information, which is the intent of quite a number of attackers. In this paper, we extend the FPD-based approach for detecting abnormal file access behaviors. We propose 3 approaches to calculate FPD values in the case of lacking training data, and we apply a k-means based unsupervised approach to distinguish between normal processes and abnormal ones. Experiment demonstrate that our unsupervised approach is still effective compared to the supervised case with training data.