As a kind of invisible spyware that records user's keystrokes, software keyloggers have posed a great threat to user privacy and security. It is difficult to detect keyloggers because they run in a hidden mode. In this paper, an immuneinspired dendritic cell algorithm (DCA) was used to detect the existence of keyloggers on an infected host machine. The basis of the detection is facilitated through the correlation (including the timing relationships) between different behaviors such as keylogging, file access and network communication. The results of the experiments show that it is a successful technique for the detection of keyloggers without responding to normally running programs.
Genetic algorithms (GAs) have long been used for large join query optimization (LJQO). Previous work takes all queries as based on one granularity to optimize GAs and compares their efficiency with other query optimization algorithms. However, we believe that large join queries are based on a granularity that is too large (1) to optimize GAs and (2) to compare the efficiency of different randomized optimization algorithms. Besides, while previous work only discusses the efficiency of basic GAs for LJQO, we believe that hybrid GAs reduce search space to improve GAs efficiency.We will present a genetic optimization model which includes factors affecting the efficiency of GAs. In this model, the query model is the granularity upon which GAs are optimized. Based on six typical query models, experiments have been done, first, to optimize four classes of GAs; and second, to prove the rationality of the query model as a trade-off between the efficiency and robustness of GAs. Finally, we will provide suggestions for choosing one of four classes of GAs and for the settings and combinations of components of GAs.
Although perovskite solar cells (PSCs) have made great achievements during the past few years, the efficiency of PSCs is only up to 25.5%, which is comparable to silicon-based solar cells. However, long-term stability is still an important problem for future commercialization. Enormous efforts have been made to prolong the lifetime of PSCs. The novel passivation strategy and advanced encapsulation are investigated, and great achievements are acquired. However, research on the basic understanding of the perovskite structure and the fabrication process of PSCs is rare, which stints the initial research for the abecedarian. At the same time, the defects among the perovskite film caused by the uncontrollable crystallization process and the fragile ionic nature also deteriorate the efficiency and stability of the perovskite devices. Herein, we summarized the investigations of the mechanism for perovskite materials and the manufacturing process of PSCs. The composition of perovskite materials, the orientation of perovskite grain, and various fabrication processes are explained. Simultaneously, the novel passivation strategy and technology are also discussed. We believe that a deeper understanding of the perovskite mechanism is beneficial to render more facilities for further development of perovskite application.
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