Increasingly taking place in online spaces, modern political conversations are typically perceived to be unproductively affirming -- siloed in so called ``echo chambers'' of exclusively like-minded discussants. Yet, to date we lack sufficient means to measure viewpoint diversity in conversations. To this end, in this paper, we operationalize two viewpoint metrics proposed for recommender systems and adapt them to the context of social media conversations. This is the first study to apply these two metrics (Representation and Fragmentation) to real world data and to consider the implications for online conversations specifically. We apply these measures to two topics -- daylight savings time (DST), which serves as a control, and the more politically polarized topic of immigration. We find that the diversity scores for both Fragmentation and Representation are lower for immigration than for DST. Further, we find that while pro-immigrant views receive consistent pushback on the platform, anti-immigrant views largely operate within echo chambers. We observe less severe yet similar patterns for DST. Taken together, Representation and Fragmentation paint a meaningful and important new picture of viewpoint diversity.

Modern robotic systems are required to operate in challenging environments, which demand reliable localization under challenging conditions. LiDAR-based localization methods, such as the Iterative Closest Point (ICP) algorithm, can suffer in geometrically uninformative environments that are known to deteriorate registration performance and push optimization toward divergence along weakly constrained directions. To overcome this issue, this work proposes i) a robust multi-category (non-)localizability detection module, and ii) a localizability-aware constrained ICP optimization module and couples both in a unified manner. The proposed localizability detection is achieved by utilizing the correspondences between the scan and the map to analyze the alignment strength against the principal directions of the optimization as part of its multi-category LiDAR localizability analysis. In the second part, this localizability analysis is then tightly integrated into the scan-to-map point cloud registration to generate drift-free pose updates along well-constrained directions. The proposed method is thoroughly evaluated and compared to state-of-the-art methods in simulation and during real-world experiments, underlying the gain in performance and reliability in LiDAR-challenging scenarios. In all experiments, the proposed framework demonstrates accurate and generalizable localizability detection and robust pose estimation without environment-specific parameter tuning.

This paper proposes a new algorithm for an automatic variable selection procedure in High Dimensional Graphical Models. The algorithm selects the relevant variables for the node of interest on the basis of mutual information. Several contributions in literature have investigated the use of mutual information in selecting the appropriate number of relevant features in a large data-set, but most of them have focused on binary outcomes or required high computational effort. The algorithm here proposed overcomes these drawbacks as it is an extension of Chow and Liu's algorithm. Once, the probabilistic structure of a High Dimensional Graphical Model is determined via the said algorithm, the best path-step, including variables with the most explanatory/predictive power for a variable of interest, is determined via the computation of the entropy coefficient of determination. The latter, being based on the notion of (symmetric) Kullback-Leibler divergence, turns out to be closely connected to the mutual information of the involved variables. The application of the algorithm to a wide range of real-word and publicly data-sets has highlighted its potential and greater effectiveness compared to alternative extant methods.

本文采取了一步，为人形机器人提供自适应形态能力。我们提出了一种系统的方法，可以使机器人盖变形其形状，其整体尺寸适合人体机器人的人体测量值。更确切地说，我们提出了一个封面概念，该概念由两个主要组成部分组成：骨骼，这是一个称为Node的基本元素和一个软膜的重复，该元素将盖子包裹起来并用其运动构成变形。本文重点关注盖子骨骼，并解决了节点设计，系统建模，电动机定位以及变形系统的控制设计的挑战性问题。封面建模侧重于运动学，并提出了定义系统运动限制的系统方法。然后，我们应用遗传算法来找到运动位置，以使变形盖完全致动。最后，我们提出了控制算法，使覆盖物变为随时间变化的形状。通过进行四个不同的方尺寸盖，分别具有3x3、4x8、8x8和20x20节点的运动学模拟来验证整个方法。对于每个封面，我们应用遗传算法来选择运动位置并执行模拟以跟踪所需形状。仿真结果表明，提出的方法可确保封面跟踪具有良好跟踪性能的所需形状。

基于视觉的感知任务在机器人技术中扮演着重要角色，促进解决许多具有挑战性的情景的解决方案，例如自动无人驾驶汽车（UAV）的杂技演习以及机器人辅助的高精度手术。大多数以控制为导向的和以自负的感知问题通常是通过利用机器人状态估计作为辅助输入来解决的，尤其是当人工智能进入图片时。在这项工作中，我们建议第一次采用类似的方法（据我们所知），将目标变量引用于外部主题。我们证明了我们的一般和直观方法论如何改善深层卷积神经网络（CNN）的回归性能，并具有模棱两可的问题，例如同类3D姿势估计。通过分析三个高度差异的用例，从用机器人臂抓住到具有袖珍尺寸无人机的人类受试者，我们的结果始终将R2度量提高到+0.514，而不是其无状态基准。最后，我们验证了人类姿势估计任务中闭环自动袋大小的无人机的现场性能。我们的结果表明，在我们的状态CNN的平均绝对误差上，平均降低了24％。

水生运动是生物学家和工程师感兴趣的经典流体结构相互作用（FSI）问题。求解完全耦合的FSI方程，用于不可压缩的Navier-Stokes和有限的弹性在计算上是昂贵的。在这种系统中，优化机器人游泳器设计通常涉及在已经昂贵的模拟之上繁琐的，无梯度的程序。为了应对这一挑战，我们提出了一种针对FSI的新颖，完全可区分的混合方法，该方法结合了2D直接数值模拟，用于游泳器的可变形固体结构和物理受限的神经网络替代物，以捕获流体的流体动力效应。对于游泳者身体的可变形实心模拟，我们使用来自计算机图形领域的最新技术来加快有限元方法（FEM）。对于流体模拟，我们使用经过基于物理损耗功能的U-NET体系结构来预测每个时间步骤的流场。使用沉浸式边界方法（IBM）在我们游泳器边界的边界周围采样了来自神经网络的压力和速度场输出，以准确有效地计算其游泳运动。我们证明了混合模拟器在2D Carangiform游泳器上的计算效率和可不同性。由于可怜性，该模拟器可用于通过基于直接梯度的优化浸入流体中的软体体系的控件设计。

Accurate simulation of soft mechanisms under dynamic actuation is critical for the design of soft robots. We address this gap with our differentiable simulation tool by learning the material parameters of our soft robotic fish. On the example of a soft robotic fish, we demonstrate an experimentally-verified, fast optimization pipeline for learning the material parameters from quasi-static data via differentiable simulation and apply it to the prediction of dynamic performance. Our method identifies physically plausible Young's moduli for various soft silicone elastomers and stiff acetal copolymers used in creation of our three different robotic fish tail designs. We show that our method is compatible with varying internal geometry of the actuators, such as the number of hollow cavities. Our framework allows high fidelity prediction of dynamic behavior for composite bi-morph bending structures in real hardware to millimeter-accuracy and within 3 percent error normalized to actuator length. We provide a differentiable and robust estimate of the thrust force using a neural network thrust predictor; this estimate allows for accurate modeling of our experimental setup measuring bollard pull. This work presents a prototypical hardware and simulation problem solved using our differentiable framework; the framework can be applied to higher dimensional parameter inference, learning control policies, and computational design due to its differentiable character.