Abstract-We propose a novel multiple kernel learning (MKL) algorithm with a group lasso regularizer, called group lasso regularized MKL (GL-MKL), for heterogeneous feature fusion and variable selection. For problems of feature fusion, assigning a group of base kernels for each feature type in an MKL framework provides a robust way in fitting data extracted from different feature domains. Adding a mixed norm constraint (i.e., group lasso) as the regularizer, we can enforce the sparsity at the group/feature level and automatically learn a compact feature set for recognition purposes. More precisely, our GL-MKL determines the optimal base kernels, including the associated weights and kernel parameters, and results in improved recognition performance. Besides, our GL-MKL can also be extended to address heterogeneous variable selection problems. For such problems, we aim to select a compact set of variables (i.e., feature attributes) for comparable or improved performance. Our proposed method does not need to exhaustively search for the entire variable space like prior sequential-based variable selection methods did, and we do not require any prior knowledge on the optimal size of the variable subset either. To verify the effectiveness and robustness of our GL-MKL, we conduct experiments on video and image datasets for heterogeneous feature fusion, and perform variable selection on various UCI datasets.Index Terms-Feature fusion, multiple kernel learning, variable selection.

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Data fusion is to merge the results of multiple independent retrieval models into a single ranked list. Several earlier studies have shown that the combination of different models can improve the retrieval performance better than using any of the individual models. Although many promising results have been given by supervised fusion methods, training data sampling has attracted little attention in previous work of data fusion. By observing some evaluations on TREC and NTCIR datasets, we found that the performance of one model varied largely from one training example to another, so that not all training examples were equivalently effective. In this paper, we propose two novel approaches: greedy and boosting approaches, which select effective training data by query sampling to improve the performance of supervised data fusion algorithms such as BayesFuse, probFuse and MAPFuse. Extensive experiments were conducted on five data sets including TREC-3,4,5 and NTCIR-3,4. The results show that our sampling approaches can significantly improve the retrieval performance of those data fusion methods.

Given a query image containing the object of interest (OOI), we propose a novel learning framework for retrieving relevant frames from the input video sequence. While techniques based on object matching have been applied to solve this task, their performance would be typically limited due to the lack of capabilities in handling variations in visual appearances of the OOI across video frames. Our proposed framework can be viewed as a weakly supervised approach, which only requires a small number of (randomly selected) relevant and irrelevant frames from the input video for performing satisfactory retrieval performance. By utilizing frame-level label information of such video frames together with the query image, we propose a novel query-adaptive multiple instance learning algorithm, which exploits the visual appearance information of the OOI from the query and that of the aforementioned video frames. As a result, the derived learning model would exhibit additional discriminating abilities while retrieving relevant instances. Experiments on two real-world video data sets would confirm the effectiveness and robustness of our proposed approach.