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 Yang, Guang-Zhong


Synergistic Development of Perovskite Memristors and Algorithms for Robust Analog Computing

arXiv.org Artificial Intelligence

Analog computing using non-volatile memristors has emerged as a promising solution for energy-efficient deep learning. New materials, like perovskites-based memristors are recently attractive due to their cost-effectiveness, energy efficiency and flexibility. Yet, challenges in material diversity and immature fabrications require extensive experimentation for device development. Moreover, significant non-idealities in these memristors often impede them for computing. Here, we propose a synergistic methodology to concurrently optimize perovskite memristor fabrication and develop robust analog DNNs that effectively address the inherent non-idealities of these memristors. Employing Bayesian optimization (BO) with a focus on usability, we efficiently identify optimal materials and fabrication conditions for perovskite memristors. Meanwhile, we developed "BayesMulti", a DNN training strategy utilizing BO-guided noise injection to improve the resistance of analog DNNs to memristor imperfections. Our approach theoretically ensures that within a certain range of parameter perturbations due to memristor non-idealities, the prediction outcomes remain consistent. Our integrated approach enables use of analog computing in much deeper and wider networks, which significantly outperforms existing methods in diverse tasks like image classification, autonomous driving, species identification, and large vision-language models, achieving up to 100-fold improvements. We further validate our methodology on a 10$\times$10 optimized perovskite memristor crossbar, demonstrating high accuracy in a classification task and low energy consumption. This study offers a versatile solution for efficient optimization of various analog computing systems, encompassing both devices and algorithms.


Efficient Domain Adaptation for Endoscopic Visual Odometry

arXiv.org Artificial Intelligence

Visual odometry plays a crucial role in endoscopic imaging, yet the scarcity of realistic images with ground truth poses poses a significant challenge. Therefore, domain adaptation offers a promising approach to bridge the pre-operative planning domain with the intra-operative real domain for learning odometry information. However, existing methodologies suffer from inefficiencies in the training time. In this work, an efficient neural style transfer framework for endoscopic visual odometry is proposed, which compresses the time from pre-operative planning to testing phase to less than five minutes. For efficient traing, this work focuses on training modules with only a limited number of real images and we exploit pre-operative prior information to dramatically reduce training duration. Moreover, during the testing phase, we propose a novel Test Time Adaptation (TTA) method to mitigate the gap in lighting conditions between training and testing datasets. Experimental evaluations conducted on two public endoscope datasets showcase that our method achieves state-of-the-art accuracy in visual odometry tasks while boasting the fastest training speeds. These results demonstrate significant promise for intra-operative surgery applications.


Constrained-Space Optimization and Reinforcement Learning for Complex Tasks

arXiv.org Artificial Intelligence

Learning from Demonstration is increasingly used for transferring operator manipulation skills to robots. In practice, it is important to cater for limited data and imperfect human demonstrations, as well as underlying safety constraints. This paper presents a constrained-space optimization and reinforcement learning scheme for managing complex tasks. Through interactions within the constrained space, the reinforcement learning agent is trained to optimize the manipulation skills according to a defined reward function. After learning, the optimal policy is derived from the well-trained reinforcement learning agent, which is then implemented to guide the robot to conduct tasks that are similar to the experts' demonstrations. The effectiveness of the proposed method is verified with a robotic suturing task, demonstrating that the learned policy outperformed the experts' demonstrations in terms of the smoothness of the joint motion and end-effector trajectories, as well as the overall task completion time.


Instantiation-Net: 3D Mesh Reconstruction from Single 2D Image for Right Ventricle

arXiv.org Machine Learning

-- 3D shape instantiation which reconstructs the 3D shape of a target from limited 2D images or projections is an emerging technique for surgical intervention. It improves the currently less-informative and insufficient 2D navigation schemes for robot-assisted Minimally Invasive Surgery (MIS) to 3D navigation. Previously, a general and registration-free framework was proposed for 3D shape instantiation based on Kernel Partial Least Square Regression (KPLSR), requiring manually segmented anatomical structures as the prerequisite. Two hyper-parameters including the Gaussian width and component number also need to be carefully adjusted. Deep Convolutional Neural Network (DCNN) based framework has also been proposed to reconstruct a 3D point cloud from a single 2D image, with end-to-end and fully automatic learning. In this paper, an Instantiation-Net is proposed to reconstruct the 3D mesh of a target from its a single 2D image, by using DCNN to extract features from the 2D image and Graph Convolutional Network (GCN) to reconstruct the 3D mesh, and using Fully Connected (FC) layers to connect the DCNN to GCN. Detailed validation was performed to demonstrate the practical strength of the method and its potential clinical use.


Z-Net: an Asymmetric 3D DCNN for Medical CT Volume Segmentation

arXiv.org Machine Learning

-- Accurate volume segmentation from the Computed T omography (CT) scan is a common prerequisite for preoperative planning, intra-operative guidance and quantitative assessment of therapeutic outcomes in robot-assisted Minimally Invasive Surgery (MIS). The use of 3D Deep Convolutional Neural Network (DCNN) is a viable solution for this task but is memory intensive. The use of patch division can mitigate this issue in practice, but can cause discontinuities between the adjacent patches and severe class-imbalances within individual sub-volumes. This paper presents a new patch division approach - Patch-512 to tackle the class-imbalance issue by preserving a full field-of-view of the objects in the XY planes. T o achieve better segmentation results based on these asymmetric patches, a 3D DCNN architecture using asymmetrical separable convolutions is proposed. The proposed network, called Z-Net, can be seamlessly integrated into existing 3D DCNNs such as 3D U-Net and V-Net, for improved volume segmentation. Detailed validation of the method is provided for CT aortic, liver and lung segmentation, demonstrating the effectiveness and practical value of the method for intra-operative 3D navigation in robot-assisted MIS. Medical volume segmentation, which labels the class of each voxel in a 3D volume, is a fundamental task in medical image analysis.


Atrous Convolutional Neural Network (ACNN) for Semantic Image Segmentation with full-scale Feature Maps

arXiv.org Machine Learning

Deep Convolutional Neural Networks (DCNNs) are used extensively in biomedical image segmentation. However, current DCNNs usually use down sampling layers for increasing the receptive field and gaining abstract semantic information. These down sampling layers decrease the spatial dimension of feature maps, which can be detrimental to semantic image segmentation. Atrous convolution is an alternative for the down sampling layer. It increases the receptive field whilst maintains the spatial dimension of feature maps. In this paper, a method for effective atrous rate setting is proposed to achieve the largest and fully-covered receptive field with a minimum number of atrous convolutional layers. Furthermore, different atrous blocks, shortcut connections and normalization methods are explored to select the optimal network structure setting. These lead to a new and full-scale DCNN - Atrous Convolutional Neural Network (ACNN), which incorporates cascaded atrous II-blocks, residual learning and Fine Group Normalization (FGN). Application results of the proposed ACNN to Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) image segmentation demonstrate that the proposed ACNN can achieve comparable segmentation Dice Similarity Coefficients (DSCs) to U-Net, optimized U-Net and hybrid network, but with significantly reduced trainable parameters due to the use of full-scale feature maps and therefore computationally is much more efficient for both the training and inference.


Artificial Intelligence and Robotics

arXiv.org Artificial Intelligence

The recent successes of AI have captured the wildest imagination of both the scientific communities and the general public. Robotics and AI amplify human potentials, increase productivity and are moving from simple reasoning towards human-like cognitive abilities. Current AI technologies are used in a set area of applications, ranging from healthcare, manufacturing, transport, energy, to financial services, banking, advertising, management consulting and government agencies. The global AI market is around 260 billion USD in 2016 and it is estimated to exceed 3 trillion by 2024. To understand the impact of AI, it is important to draw lessons from it's past successes and failures and this white paper provides a comprehensive explanation of the evolution of AI, its current status and future directions.