系列弹性执行器（SEA）具有固有的合规性，可为机器人提供安全的扭矩来源，这些源是与各种环境相互作用的机器人，包括人类。这些应用对海体扭矩控制器有很高的要求，扭矩响应以及与其环境的相互作用行为。为了区分现有技术的扭矩控制器，这项工作正在引入统一的理论和实验框架，其基于它们的扭矩传递行为，表观阻抗行为，特别是表观阻抗的钝化性，即它们的相互作用稳定性，也是如此作为对传感器噪声的敏感性。我们比较经典的海上控制方法，如级联PID控制器和全状态反馈控制器，使用干扰观察者，加速反馈和适应规则，具有先进的控制器。仿真和实验证明了稳定的相互作用，高带宽和低噪声水平之间的折衷。基于这些权衡，可以基于与各个环境的所需交互来设计和调整特定于应用程序特定控制器。

在各种条件下行走期间关节阻抗的知识与临床决策以及机器人步态培训师，腿部假体，腿矫形器和可穿戴外骨骼的发展相关。虽然步行过程中的脚踝阻抗已经通过实验评估，但尚未识别步行期间的膝盖和髋关节阻抗。在这里，我们开发并评估了下肢扰动器，以识别跑步机行走期间髋关节，膝关节和踝关节阻抗。下肢扰动器（Loper）由致动器组成，致动器通过杆连接到大腿。 Loper允许将力扰动施加到自由悬挂的腿上，同时站立在对侧腿上，带宽高达39Hz。在以最小的阻抗模式下行走时，Loper和大腿之间的相互作用力低（<5N），并且对行走图案的效果小于正常行走期间的对象内变异性。使用摆动腿动力学的非线性多体动力学模型，在摆动阶段在速度为0.5米/秒的速度的九个受试者期间估计臀部，膝关节和踝关节阻抗。所识别的模型能够预测实验反应，因为分别占髋部，膝关节和踝部的平均方差为99％，96％和77％。对受试者刚度的平均分别在34-66nm / rad，0-3.5nm / rad，0-3.5nm / rad和2.5-24nm / rad的三个时间点之间变化，分别用于臀部，膝部和踝关节。阻尼分别在1.9-4.6 nms / rad，0.02-0.14 nms / rad和0.2-2.4 nms / rad的0.02-0.14 nms / rad供应到0.2-2.4nms / rad。发达的洛普勒对不受干扰的行走模式具有可忽略的影响，并且允许在摆动阶段识别臀部，膝关节和踝关节阻抗。

可解释的机器学习旨在了解复杂的黑盒系统的推理过程，这些系统因缺乏解释性而臭名昭著。一种不断增长的解释方法是通过反事实解释，这超出了为什么系统做出一定决定，以进一步提供有关用户可以采取哪些方法来改变结果的建议。反事实示例必须能够应对黑框分类器的原始预测，同时还满足实用应用程序的各种约束。这些限制存在于一个和另一个之间的权衡处，对现有作品提出了根本的挑战。为此，我们提出了一个基于随机学习的框架，可以有效地平衡反事实权衡。该框架由具有互补角色的一代和特征选择模块组成：前者的目标是建模有效的反事实的分布，而后者则以允许可区分训练和摊销优化的方式执行其他约束。我们证明了我们方法在产生可行和合理的反事实中的有效性，这些反事实比现有方法更多样化，尤其是比具有相同能力的对应物更有效的方式。

从有限的资源中获得最大收益可以进步自然语言处理（NLP）研究和实践，同时保守资源。这些资源可能是数据，时间，存储或能源。NLP的最新工作从缩放率产生了有趣的结果。但是，仅使用比例来改善结果意味着资源消耗也会扩展。这种关系激发了对有效方法的研究，这些方法需要更少的资源才能获得相似的结果。这项调查涉及NLP效率的方法和发现，旨在指导该领域的新研究人员并激发新方法的发展。

在过去二十年中，识别具有不同纵向数据趋势的群体的方法已经成为跨越许多研究领域的兴趣。为了支持研究人员，我们总结了文献关于纵向聚类的指导。此外，我们提供了一种纵向聚类方法，包括基于基团的轨迹建模（GBTM），生长混合模拟（GMM）和纵向K平均值（KML）。该方法在基本级别引入，并列出了强度，限制和模型扩展。在最近数据收集的发展之后，将注意这些方法的适用性赋予密集的纵向数据（ILD）。我们展示了使用R.中可用的包在合成数据集上的应用程序的应用。

As language models (LMs) scale, they develop many novel behaviors, good and bad, exacerbating the need to evaluate how they behave. Prior work creates evaluations with crowdwork (which is time-consuming and expensive) or existing data sources (which are not always available). Here, we automatically generate evaluations with LMs. We explore approaches with varying amounts of human effort, from instructing LMs to write yes/no questions to making complex Winogender schemas with multiple stages of LM-based generation and filtering. Crowdworkers rate the examples as highly relevant and agree with 90-100% of labels, sometimes more so than corresponding human-written datasets. We generate 154 datasets and discover new cases of inverse scaling where LMs get worse with size. Larger LMs repeat back a dialog user's preferred answer ("sycophancy") and express greater desire to pursue concerning goals like resource acquisition and goal preservation. We also find some of the first examples of inverse scaling in RL from Human Feedback (RLHF), where more RLHF makes LMs worse. For example, RLHF makes LMs express stronger political views (on gun rights and immigration) and a greater desire to avoid shut down. Overall, LM-written evaluations are high-quality and let us quickly discover many novel LM behaviors.

In this paper, we propose a novel graph kernel, namely the Quantum-based Entropic Subtree Kernel (QESK), for Graph Classification. To this end, we commence by computing the Average Mixing Matrix (AMM) of the Continuous-time Quantum Walk (CTQW) evolved on each graph structure. Moreover, we show how this AMM matrix can be employed to compute a series of entropic subtree representations associated with the classical Weisfeiler-Lehman (WL) algorithm. For a pair of graphs, the QESK kernel is defined by computing the exponentiation of the negative Euclidean distance between their entropic subtree representations, theoretically resulting in a positive definite graph kernel. We show that the proposed QESK kernel not only encapsulates complicated intrinsic quantum-based structural characteristics of graph structures through the CTQW, but also theoretically addresses the shortcoming of ignoring the effects of unshared substructures arising in state-of-the-art R-convolution graph kernels. Moreover, unlike the classical R-convolution kernels, the proposed QESK can discriminate the distinctions of isomorphic subtrees in terms of the global graph structures, theoretically explaining the effectiveness. Experiments indicate that the proposed QESK kernel can significantly outperform state-of-the-art graph kernels and graph deep learning methods for graph classification problems.

The NASA Astrophysics Data System (ADS) is an essential tool for researchers that allows them to explore the astronomy and astrophysics scientific literature, but it has yet to exploit recent advances in natural language processing. At ADASS 2021, we introduced astroBERT, a machine learning language model tailored to the text used in astronomy papers in ADS. In this work we: - announce the first public release of the astroBERT language model; - show how astroBERT improves over existing public language models on astrophysics specific tasks; - and detail how ADS plans to harness the unique structure of scientific papers, the citation graph and citation context, to further improve astroBERT.

Behavior constrained policy optimization has been demonstrated to be a successful paradigm for tackling Offline Reinforcement Learning. By exploiting historical transitions, a policy is trained to maximize a learned value function while constrained by the behavior policy to avoid a significant distributional shift. In this paper, we propose our closed-form policy improvement operators. We make a novel observation that the behavior constraint naturally motivates the use of first-order Taylor approximation, leading to a linear approximation of the policy objective. Additionally, as practical datasets are usually collected by heterogeneous policies, we model the behavior policies as a Gaussian Mixture and overcome the induced optimization difficulties by leveraging the LogSumExp's lower bound and Jensen's Inequality, giving rise to a closed-form policy improvement operator. We instantiate offline RL algorithms with our novel policy improvement operators and empirically demonstrate their effectiveness over state-of-the-art algorithms on the standard D4RL benchmark.

Reducing the quantity of annotations required for supervised training is vital when labels are scarce and costly. This reduction is especially important for semantic segmentation tasks involving 3D datasets that are often significantly smaller and more challenging to annotate than their image-based counterparts. Self-supervised pre-training on large unlabelled datasets is one way to reduce the amount of manual annotations needed. Previous work has focused on pre-training with point cloud data exclusively; this approach often requires two or more registered views. In the present work, we combine image and point cloud modalities, by first learning self-supervised image features and then using these features to train a 3D model. By incorporating image data, which is often included in many 3D datasets, our pre-training method only requires a single scan of a scene. We demonstrate that our pre-training approach, despite using single scans, achieves comparable performance to other multi-scan, point cloud-only methods.