Aiming at the mechanical system related to multi-component failure， a reliability evaluation method of multi-component system based on time-varying Copula function was proposed. Firstly， the nonlinear Wiener process was introduced to characterize the performance degradation process， and the Copula function was used to characterize the correlation between multiple component failures. Secondly， based on the evolutionary equation of the Copula function approximation of the Fourier series， the fitting effects of the Fourier series on common time-varying forms were verified by Monte Carlo （MC） simulation. In addition， the likelihood ratio statistic was used to test the existence of time-varying correlation， indicating the necessity of time-varying correlation research. The example analysis shows that compared with the static correlation model， the time-varying correlation model has the log-likelihood function value increased by 4.36%， and the Akaike Information Criterion （AIC） decreased by 3.81%， achieving more accurate reliability evaluation results.

ElectroCardioGram （ECG） data usually contain many diseases， and ECG diagnosis is a typical multi-label classification problem. In RAndom k-labELsets （RAKEL） algorithm， one of multi-label classification methods， all labels are randomly decomposed into several labelsets of size k， and a Label Powerset （LP） classifier is established for training； however， the lack of sufficient consideration of correlation between labels makes the LP classifier obtain quite few samples corresponding to certain label combinations， which affects the prediction performance. To fully consider the correlation between labels， a Bayesian Network-based RAKEL （BN-RAKEL） algorithm was proposed. Firstly， the correlation between labels was found by Bayesian network to determine the candidate labelsets. Then， a feature selection method based on information gain was applied to construct the optimal feature space for each label， and the optimal feature space similarity was used for each candidate label subset to detect its correlation degree， determing the final labelsets with strong correlation. Finally， the LP classifiers were trained in the optimal feature space of the corresponding labelsets. A comparison with K-Nearest Neighbors for Multi-label Learning （ML-KNN）， RAKEL， Classifier Chains （CC） and FP-Growth based RAKEL algorithm named FI-RAKEL on the real ECG dataset showed that the proposed algorithm achieved a minimum improvement of 3.6 percentage points and 2.3percentage points in recall and F-score， respectively. Experimental results show that BN-RAKEL algorithm has good prediction performance， and can effectively improve the ECG diagnosis accuracy.

In order to solve the problem that conditional constraints (context constraints) for personalized queries in database were not fully considered, a constraint model was proposed where the context i ^+≻i-| X means that the user prefers i ⁺ than i ^- based on the constraint of context X. Association rules mining algorithm based on MaxClique was used to obtain user preferences, and Conditional Preference Mining (CPM) algorithm combined with context obtained preference rules was proposed to obtain user preferences. The experimental results show that the context preference mining model has strong preference expression ability. At the same time, under the different parameters of minimum support, minimum confidence and data scale, the experimental results of preferences mining algorithm of CPM compared with Apriori algorithm and CONTENUM algorithm show that the proposed CPM algorithm can obviously improve the generation efficiency of user preferences.

In order to protect Android platforms from the application-level privilege escalation attacks, this paper analyzed the XManDroid access control model, which has better ability on fighting these attacks, especially the collusion attack on the covert channel. To address the problem that XManDroid could not detect the multi-application and multi-permissions collusion attacks, this paper proposed an improved mandatory access control model which recorded the communication history of applications by building an IPC links colored diagram. At last, the test result on the prototype system show that the new model can solve the problem in the XManDroid well.