Materials
Convergence and stability of Q-learning in Hierarchical Reinforcement Learning
Manenti, Massimiliano, Iannelli, Andrea
Decision-making architectures have played a central role for decades [1] both in engineering and other domains, e.g., guidance, navigation and control of Apollo missions [2], chemical plants [3], smart grids [4], unmanned aerial vehicles [5], recommender systems [6], and algorithms [7]. Moreover, architectures are ubiquitous in nature, e.g., diversity in the nervous system enables humans to have fast and accurate sensorimotor control [8]. Reinforcement Learning (RL) is a framework in which an agent learns to make sequential decisions through interaction with an environment in order to maximize cumulative reward [9]. Decision-making architectures have also been proposed and studied in RL. Hierarchical Reinforcement Learning (HRL) is a subfield of RL that deals with hierarchical structures for decision-making agents. Prospective advantages include improved long-term credit assignment, continual learning, interpretability, and the integration of preexisting policies [10], [11].
General Catalyst CEO Hemant Taneja on Aligning Profit With Purpose
Booth is a reporter at TIME. Hemant Taneja, CEO, General Catalyst speaks on stage during The Summit on U.S. Resilience hosted by General Catalyst Institute at The Salamander on Nov. 17, 2025 in Washington, DC. Hemant Taneja, CEO, General Catalyst speaks on stage during The Summit on U.S. Resilience hosted by General Catalyst Institute at The Salamander on Nov. 17, 2025 in Washington, DC. Booth is a reporter at TIME. Hemant Taneja, who leads one of the world's largest venture firms, believes doing good isn't just the right thing to do.
The Best Chef's Knives of 2025. We Tested Nearly Two Dozen to Find Our Favorites
The chef's knife is the workhorse of the kitchen. We sliced, diced, and minced to find the best for every home chef. A Close Second Chef's Knife (Made From High-Carbon Stainless Steel) Zwilling Four Star 8-Inch Chef's Knife Not all knives are created equal, and a chef's knife is given that name for a reason. Like the proverbial dog to man, a chef needs their knife. Arguably the most important multipurpose tool you can find in a kitchen, it's the chef's main weapon--it can slice, dice, and chop ingredients with speed and precision. A chef's knife generally has a super-sharp end point and a curved, sloping edge. This curve is what makes the chef knife stand out, as it's designed to work with the natural rocking motion for quick chopping that also allows for finer cuts. With technology like ovens with cameras inside and AI-enabled refrigerators, the chef's knife remains the simple tool necessary for any kitchen.
VersaPants: A Loose-Fitting Textile Capacitive Sensing System for Lower-Body Motion Capture
Kasap, Deniz, Najafi, Taraneh Aminosharieh, Thevenot, Jรฉrรดme Paul Rรฉmy, Dan, Jonathan, Albini, Stefano, Atienza, David
We present VersaPants, the first loose-fitting, textile-based capacitive sensing system for lower-body motion capture, built on the open-hardware VersaSens platform. By integrating conductive textile patches and a compact acquisition unit into a pair of pants, the system reconstructs lower-body pose without compromising comfort. Unlike IMU-based systems that require user-specific fitting or camera-based methods that compromise privacy, our approach operates without fitting adjustments and preserves user privacy. VersaPants is a custom-designed smart garment featuring 6 capacitive channels per leg. We employ a lightweight Transformer-based deep learning model that maps capacitance signals to joint angles, enabling embedded implementation on edge platforms. To test our system, we collected approximately 3.7 hours of motion data from 11 participants performing 16 daily and exercise-based movements. The model achieves a mean per-joint position error (MPJPE) of 11.96 cm and a mean per-joint angle error (MPJAE) of 12.3 degrees across the hip, knee, and ankle joints, indicating the model's ability to generalize to unseen users and movements. A comparative analysis of existing textile-based deep learning architectures reveals that our model achieves competitive reconstruction performance with up to 22 times fewer parameters and 18 times fewer FLOPs, enabling real-time inference at 42 FPS on a commercial smartwatch without quantization. These results position VersaPants as a promising step toward scalable, comfortable, and embedded motion-capture solutions for fitness, healthcare, and wellbeing applications.
Incorporating Self-Rewriting into Large Language Model Reasoning Reinforcement
Yao, Jiashu, Huang, Heyan, Zeng, Shuang, Luo, Chuwei, You, WangJie, Tang, Jie, Liu, Qingsong, Guo, Yuhang, Kang, Yangyang
Through reinforcement learning (RL) with outcome correctness rewards, large reasoning models (LRMs) with scaled inference computation have demonstrated substantial success on complex reasoning tasks. However, the one-sided reward, focused solely on final correctness, limits its ability to provide detailed supervision over internal reasoning process. This deficiency leads to suboptimal internal reasoning quality, manifesting as issues like over-thinking, under-thinking, redundant-thinking, and disordered-thinking. Inspired by the recent progress in LRM self-rewarding, we introduce self-rewriting framework, where a model rewrites its own reasoning texts, and subsequently learns from the rewritten reasoning to improve the internal thought process quality. For algorithm design, we propose a selective rewriting approach wherein only "simple" samples, defined by the model's consistent correctness, are rewritten, thereby preserving all original reward signals of GRPO. For practical implementation, we compile rewriting and vanilla generation within one single batch, maintaining the scalability of the RL algorithm and introducing only ~10% overhead. Extensive experiments on diverse tasks with different model sizes validate the effectiveness of self-rewriting. In terms of the accuracy-length tradeoff, the self-rewriting approach achieves improved accuracy (+0.6) with substantially shorter reasoning (-46%) even without explicit instructions in rewriting prompts to reduce reasoning length, outperforming existing strong baselines. In terms of internal reasoning quality, self-rewriting achieves significantly higher scores (+7.2) under the LLM-as-a-judge metric, successfully mitigating internal reasoning flaws.
Graph Diffusion Counterfactual Explanation
Bechtoldt, David, Bender, Sidney
Machine learning models that operate on graph-structured data, such as molecular graphs or social networks, often make accurate predictions but offer little insight into why certain predictions are made. Counterfactual explanations address this challenge by seeking the closest alternative scenario where the model's prediction would change. Although counterfactual explanations are extensively studied in tabular data and computer vision, the graph domain remains comparatively underexplored. Constructing graph counterfactuals is intrinsically difficult because graphs are discrete and non-euclidean objects. We introduce Graph Diffusion Counterfactual Explanation, a novel framework for generating counterfactual explanations on graph data, combining discrete diffusion models and classifier-free guidance. We empirically demonstrate that our method reliably generates in-distribution as well as minimally structurally different counterfactuals for both discrete classification targets and continuous properties.
Towards a Safer and Sustainable Manufacturing Process: Material classification in Laser Cutting Using Deep Learning
Salem, Mohamed Abdallah, Ashur, Hamdy Ahmed, Elshinnawy, Ahmed
Laser cutting is a widely adopted technology in material processing across various industries, but it generates a significant amount of dust, smoke, and aerosols during operation, posing a risk to both the environment and workers' health. Speckle sensing has emerged as a promising method to monitor the cutting process and identify material types in real-time. This paper proposes a material classification technique using a speckle pattern of the material's surface based on deep learning to monitor and control the laser cutting process. The proposed method involves training a convolutional neural network (CNN) on a dataset of laser speckle patterns to recognize distinct material types for safe and efficient cutting. Previous methods for material classification using speckle sensing may face issues when the color of the laser used to produce the speckle pattern is changed. Experiments conducted in this study demonstrate that the proposed method achieves high accuracy in material classification, even when the laser color is changed. The model achieved an accuracy of 98.30 % on the training set and 96.88% on the validation set. Furthermore, the model was evaluated on a set of 3000 new images for 30 different materials, achieving an F1-score of 0.9643. The proposed method provides a robust and accurate solution for material-aware laser cutting using speckle sensing.
Parameter-aware high-fidelity microstructure generation using stable diffusion
Phan, Hoang Cuong, Tran, Minh Tien, Lee, Chihun, Kim, Hoheok, Oh, Sehyeok, Kim, Dong-Kyu, Lee, Ho Won
Synthesizing realistic microstructure images conditioned on processing parameters is crucial for understanding process-structure relationships in materials design. However, this task remains challenging due to limited training micrographs and the continuous nature of processing variables. To overcome these challenges, we present a novel process-aware generative modeling approach based on Stable Diffusion 3.5 Large (SD3.5-Large), a state-of-the-art text-to-image diffusion model adapted for microstructure generation. Our method introduces numeric-aware embeddings that encode continuous variables (annealing temperature, time, and magnification) directly into the model's conditioning, enabling controlled image generation under specified process conditions and capturing process-driven microstructural variations. To address data scarcity and computational constraints, we fine-tune only a small fraction of the model's weights via DreamBooth and Low-Rank Adaptation (LoRA), efficiently transferring the pre-trained model to the materials domain. We validate realism using a semantic segmentation model based on a fine-tuned U-Net with a VGG16 encoder on 24 labeled micrographs. It achieves 97.1% accuracy and 85.7% mean IoU, outperforming previous methods. Quantitative analyses using physical descriptors and spatial statistics show strong agreement between synthetic and real microstructures. Specifically, two-point correlation and lineal-path errors remain below 2.1% and 0.6%, respectively. Our method represents the first adaptation of SD3.5-Large for process-aware microstructure generation, offering a scalable approach for data-driven materials design.
A Startup's Bid to Dim the Sun
The gloomy arguments in favor of solar geoengineering are compelling; so are the even gloomier counter-arguments. Stardust is the name of a small startup with enormous ambitions. The company, which is based in Israel and registered in Delaware, proposes to do nothing less than dim the sun. Its business plan is modelled on volcanoes. In a major eruption, millions of tons of sulfur dioxide get thrown up into the stratosphere.