Training model-free intelligent agents in complex real-world scenarios using reinforcement learning (RL) often necessitates simulation-based environments due to high physical expenses. However, when simulation takes a long time, e.g., in an unsteady 3D fluid simulation with interactions to the controllable solids, existing RL algorithms meet difficulty to accomplish training within a reasonable timeframes. In this paper, we propose a novel multi-level framework for RL to accelerate convergence as the first attempt to address this difficulty. Motivated by the idea of multi-grid solver, the control policy on a virtual agent over time can be decomposed into different frequency levels, which can be progressively learned via a set of simulations in a coarse-to-fine manner. It is expected that most RL trials are performed in coarser simulations to learn lower control frequency levels with more efficient convergence, while higher frequency levels require much less RL trials, thus significantly accelerating the learning process. To implement our idea, we designed a novel multi-level residual network with a filter module attached, where each level of the network is learned by performing RL for a given simulation resolution. The proposed framework is evaluated by conducting policy learning experiments on a virtual aerial (2D) and an underwater (3D) robot, both requiring time-consuming physical simulations. Our results demonstrate a decrease in almost half in learning time compared to a direct RL approach, while achieving similar control performance.

Leukemia classification relies on a detailed cytomorphological examination of Bone Marrow (BM) smear. However, applying existing deep-learning methods to it is facing two significant limitations. Firstly, these methods require large-scale datasets with expert annotations at the cell level for good results and typically suffer from poor generalization. Secondly, they simply treat the BM cytomorphological examination as a multi-class cell classification task, thus failing to exploit the correlation among leukemia subtypes over different hierarchies. Therefore, BM cytomorphological estimation as a time-consuming and repetitive process still needs to be done manually by experienced cytologists. Recently, Multi-Instance Learning (MIL) has achieved much progress in data-efficient medical image processing, which only requires patient-level labels (which can be extracted from the clinical reports). In this paper, we propose a hierarchical MIL framework and equip it with Information Bottleneck (IB) to tackle the above limitations. First, to handle the patient-level label, our hierarchical MIL framework uses attention-based learning to identify cells with high diagnostic values for leukemia classification in different hierarchies. Then, following the information bottleneck principle, we propose a hierarchical IB to constrain and refine the representations of different hierarchies for better accuracy and generalization. By applying our framework to a large-scale childhood acute leukemia dataset with corresponding BM smear images and clinical reports, we show that it can identify diagnostic-related cells without the need for cell-level annotations and outperforms other comparison methods. Furthermore, the evaluation conducted on an independent test cohort demonstrates the high generalizability of our framework.

With the growth of online shopping for fashion products, accurate fashion recommendation has become a critical problem. Meanwhile, social networks provide an open and new data source for personalized fashion analysis. In this work, we study the problem of personalized fashion recommendation from social media data, i.e. recommending new outfits to social media users that fit their fashion preferences. To this end, we present an item-to-set metric learning framework that learns to compute the similarity between a set of historical fashion items of a user to a new fashion item. To extract features from multi-modal street-view fashion items, we propose an embedding module that performs multi-modality feature extraction and cross-modality gated fusion. To validate the effectiveness of our approach, we collect a real-world social media dataset. Extensive experiments on the collected dataset show the superior performance of our proposed approach.