The number of international benchmarking competitions is steadily increasing in various fields of machine learning (ML) research and practice. So far, however, little is known about the common practice as well as bottlenecks faced by the community in tackling the research questions posed. To shed light on the status quo of algorithm development in the specific field of biomedical imaging analysis, we designed an international survey that was issued to all participants of challenges conducted in conjunction with the IEEE ISBI 2021 and MICCAI 2021 conferences (80 competitions in total). The survey covered participants' expertise and working environments, their chosen strategies, as well as algorithm characteristics. A median of 72% challenge participants took part in the survey. According to our results, knowledge exchange was the primary incentive (70%) for participation, while the reception of prize money played only a minor role (16%). While a median of 80 working hours was spent on method development, a large portion of participants stated that they did not have enough time for method development (32%). 25% perceived the infrastructure to be a bottleneck. Overall, 94% of all solutions were deep learning-based. Of these, 84% were based on standard architectures. 43% of the respondents reported that the data samples (e.g., images) were too large to be processed at once. This was most commonly addressed by patch-based training (69%), downsampling (37%), and solving 3D analysis tasks as a series of 2D tasks. K-fold cross-validation on the training set was performed by only 37% of the participants and only 50% of the participants performed ensembling based on multiple identical models (61%) or heterogeneous models (39%). 48% of the respondents applied postprocessing steps.

The ubiquity of edge devices has led to a growing amount of unlabeled data produced at the edge. Deep learning models deployed on edge devices are required to learn from these unlabeled data to continuously improve accuracy. Self-supervised representation learning has achieved promising performances using centralized unlabeled data. However, the increasing awareness of privacy protection limits centralizing the distributed unlabeled image data on edge devices. While federated learning has been widely adopted to enable distributed machine learning with privacy preservation, without a data selection method to efficiently select streaming data, the traditional federated learning framework fails to handle these huge amounts of decentralized unlabeled data with limited storage resources on edge. To address these challenges, we propose a Federated on-device Contrastive learning framework with Coreset selection, which we call FedCoCo, to automatically select a coreset that consists of the most representative samples into the replay buffer on each device. It preserves data privacy as each client does not share raw data while learning good visual representations. Experiments demonstrate the effectiveness and significance of the proposed method in visual representation learning.

在皮肤病学诊断中，移动皮肤病学助理收集的私人数据存在于患者的分布式移动设备上。联合学习（FL）可以使用分散数据来训练模型，同时保持数据本地化。现有的FL方法假设所有数据都有标签。但是，由于高标签成本，医疗数据通常没有完整的标签。自我监督的学习（SSL）方法，对比度学习（CL）和蒙版自动编码器（MAE）可以利用未标记的数据来预先培训模型，然后用有限的标签进行微调。但是，组合SSL和FL有独特的挑战。例如，CL需要不同的数据，但每个设备仅具有有限的数据。对于MAE而言，尽管基于视觉变压器（VIT）的MAE在集中学习中具有更高的准确性，但尚未研究MAE在未标记数据的FL中的性能。此外，服务器和客户端之间的VIT同步与传统CNN不同。因此，需要设计特殊的同步方法。在这项工作中，我们提出了两个联邦自制的学习框架，用于具有有限标签的皮肤病学诊断。第一个具有较低的计算成本，适用于移动设备。第二个具有高精度，适合高性能服务器。根据CL，我们提出了与功能共享（FedClf）的联合对比度学习。共享功能可用于不同的对比信息，而无需共享原始数据以获得隐私。根据MAE，我们提出了Fedmae。知识拆分将所学的全球知识与每个客户分开。只有全球知识才能汇总为更高的概括性能。关于皮肤病学数据集的实验表明，所提出的框架的精度优于最先进的框架。

有监督的深度学习需要大量标记的数据才能实现高性能。但是，在医学成像分析中，每个站点可能只有有限的数据和标签，这使得学习无效。联合学习（FL）可以从分散数据中学习共享模型。但是传统的FL需要全标签的数据进行培训，这非常昂贵。自我监督的对比学习（CL）可以从未标记的数据中学习进行预训练，然后进行微调，以有限的注释。但是，在FL中采用CL时，每个站点上的数据多样性有限，使联合对比度学习（FCL）无效。在这项工作中，我们提出了两个联合自制的学习框架，用于体积医学图像分割，并有限注释。第一个具有高精度，并适合高性能服务器，并具有高速连接。第二个具有较低的通信成本，适用于移动设备。在第一个框架中，在FCL期间交换了功能，以向每个站点提供各种对比度数据，以使本地CL保持原始数据的私密性。全局结构匹配将不同站点之间的统一特征空间保持一致。在第二个框架中，为了降低功能交换的通信成本，我们提出了一种优化的方法FCLOPT，该方法不依赖于负样本。为了减少模型下载的通信，我们提出了预测目标网络参数的预测目标网络更新（PTNU）。基于PTNU，我们建议距离预测（DP）以删除目标网络的大多数上传。在心脏MRI数据集上的实验表明，与最先进的技术相比，提出的两个框架显着改善了分割和泛化性能。

联合学习（FL）使分布式客户端能够学习共享模型以进行预测，同时保留每个客户端的培训数据本地。然而，现有的FL需要完全标记的培训数据，这是由于高标签成本和专业要求的要求而不方便或有时不可行。在许多现实设置中，缺乏标签会使流行不切实际。自我监督学习可以通过从未标记的数据学习来解决这一挑战，从而可以广泛使用FL。对比学习（CL）是一种自我监督的学习方法，可以有效地学习来自未标记数据的数据表示。然而，Clipers上收集的分布式数据通常在客户端之间通常不是独立和相同分布（非IID），并且每个客户端只有很少的数据类，这会降低CL和学习的表示的性能。为了解决这个问题，我们提出了由两种方法组成的联邦对比学习框架：特征融合和邻居匹配，通过该邻居匹配，以便获得更好的数据表示来实现客户端之间的统一特征空间。特征融合提供远程功能，作为每个客户端的准确对比信息，以获得更好的本地学习。邻域匹配进一步将每个客户端的本地功能对齐至远程功能，从而可以了解客户端之间的群集功能。广泛的实验表明了拟议框架的有效性。它在IID数据上以11 \％的方式表达了其他方法，并匹配集中学习的性能。

Increasing research interests focus on sequential recommender systems, aiming to model dynamic sequence representation precisely. However, the most commonly used loss function in state-of-the-art sequential recommendation models has essential limitations. To name a few, Bayesian Personalized Ranking (BPR) loss suffers the vanishing gradient problem from numerous negative sampling and predictionbiases; Binary Cross-Entropy (BCE) loss subjects to negative sampling numbers, thereby it is likely to ignore valuable negative examples and reduce the training efficiency; Cross-Entropy (CE) loss only focuses on the last timestamp of the training sequence, which causes low utilization of sequence information and results in inferior user sequence representation. To avoid these limitations, in this paper, we propose to calculate Cumulative Cross-Entropy (CCE) loss over the sequence. CCE is simple and direct, which enjoys the virtues of painless deployment, no negative sampling, and effective and efficient training. We conduct extensive experiments on five benchmark datasets to demonstrate the effectiveness and efficiency of CCE. The results show that employing CCE loss on three state-of-the-art models GRU4Rec, SASRec, and S3-Rec can reach 125.63%, 69.90%, and 33.24% average improvement of full ranking NDCG@5, respectively. Using CCE, the performance curve of the models on the test data increases rapidly with the wall clock time, and is superior to that of other loss functions in almost the whole process of model training.

The utilization of large-scale distributed renewable energy promotes the development of the multi-microgrid (MMG), which raises the need of developing an effective energy management method to minimize economic costs and keep self energy-sufficiency. The multi-agent deep reinforcement learning (MADRL) has been widely used for the energy management problem because of its real-time scheduling ability. However, its training requires massive energy operation data of microgrids (MGs), while gathering these data from different MGs would threaten their privacy and data security. Therefore, this paper tackles this practical yet challenging issue by proposing a federated multi-agent deep reinforcement learning (F-MADRL) algorithm via the physics-informed reward. In this algorithm, the federated learning (FL) mechanism is introduced to train the F-MADRL algorithm thus ensures the privacy and the security of data. In addition, a decentralized MMG model is built, and the energy of each participated MG is managed by an agent, which aims to minimize economic costs and keep self energy-sufficiency according to the physics-informed reward. At first, MGs individually execute the self-training based on local energy operation data to train their local agent models. Then, these local models are periodically uploaded to a server and their parameters are aggregated to build a global agent, which will be broadcasted to MGs and replace their local agents. In this way, the experience of each MG agent can be shared and the energy operation data is not explicitly transmitted, thus protecting the privacy and ensuring data security. Finally, experiments are conducted on Oak Ridge national laboratory distributed energy control communication lab microgrid (ORNL-MG) test system, and the comparisons are carried out to verify the effectiveness of introducing the FL mechanism and the outperformance of our proposed F-MADRL.

This paper presents a safety-critical locomotion control framework for quadrupedal robots. Our goal is to enable quadrupedal robots to safely navigate in cluttered environments. To tackle this, we introduce exponential Discrete Control Barrier Functions (exponential DCBFs) with duality-based obstacle avoidance constraints into a Nonlinear Model Predictive Control (NMPC) with Whole-Body Control (WBC) framework for quadrupedal locomotion control. This enables us to use polytopes to describe the shapes of the robot and obstacles for collision avoidance while doing locomotion control of quadrupedal robots. Compared to most prior work, especially using CBFs, that utilize spherical and conservative approximation for obstacle avoidance, this work demonstrates a quadrupedal robot autonomously and safely navigating through very tight spaces in the real world. (Our open-source code is available at github.com/HybridRobotics/quadruped_nmpc_dcbf_duality, and the video is available at youtu.be/p1gSQjwXm1Q.)

Three-dimensional (3D) ultrasound imaging technique has been applied for scoliosis assessment, but current assessment method only uses coronal projection image and cannot illustrate the 3D deformity and vertebra rotation. The vertebra detection is essential to reveal 3D spine information, but the detection task is challenging due to complex data and limited annotations. We propose VertMatch, a two-step framework to detect vertebral structures in 3D ultrasound volume by utilizing unlabeled data in semi-supervised manner. The first step is to detect the possible positions of structures on transverse slice globally, and then the local patches are cropped based on detected positions. The second step is to distinguish whether the patches contain real vertebral structures and screen the predicted positions from the first step. VertMatch develops three novel components for semi-supervised learning: for position detection in the first step, (1) anatomical prior is used to screen pseudo labels generated from confidence threshold method; (2) multi-slice consistency is used to utilize more unlabeled data by inputting multiple adjacent slices; (3) for patch identification in the second step, the categories are rebalanced in each batch to solve imbalance problem. Experimental results demonstrate that VertMatch can detect vertebra accurately in ultrasound volume and outperforms state-of-the-art methods. VertMatch is also validated in clinical application on forty ultrasound scans, and it can be a promising approach for 3D assessment of scoliosis.

Free-text rationales (FTRs) follow how humans communicate by explaining reasoning processes via natural language. A number of recent works have studied how to improve language model (LM) generalization by using FTRs to teach LMs the correct reasoning processes behind correct task outputs. These prior works aim to learn from FTRs by appending them to the LM input or target output, but this may introduce an input distribution shift or conflict with the task objective, respectively. We propose KNIFE, which distills FTR knowledge from an FTR-augmented teacher LM (takes both task input and FTR) to a student LM (takes only task input), which is used for inference. Crucially, the teacher LM's forward computation has a bottleneck stage in which all of its FTR states are masked out, which pushes knowledge from the FTR states into the task input/output states. Then, FTR knowledge is distilled to the student LM by training its task input/output states to align with the teacher LM's. On two question answering datasets, we show that KNIFE significantly outperforms existing FTR learning methods, in both fully-supervised and low-resource settings.