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【4k 硬核科普】130万 vs 96万:多少个地球能填满太阳?引出一个人类400年的难题!
李永乐老师· 2025-11-17 09:30
Core Argument - The video explores how many Earths can fit inside the Sun, initially calculating based on volume ratio (approximately 1300000) and then adjusting for sphere packing efficiency (approximately 960000) [1] - It delves into the mathematical problem of sphere packing, specifically the Kepler Conjecture, and its relevance to the initial question [1][2][3] Mathematical Concepts - The volume of a sphere is proportional to the cube of its radius (V=4πr³/3), leading to the initial volume ratio calculation [1] - The densest packing of spheres in 3D space utilizes approximately 74% of the space, a concept related to the Kepler Conjecture [1][2] - The Kepler Conjecture, concerning the densest packing of spheres, was proven using computer-assisted methods after centuries of attempts [1][2][3] Sphere Packing - Two common densest packing arrangements are Hexagonal Close Packing (HCP) and Face-Centered Cubic (FCC), both achieving approximately 7405% space utilization [2] - The video explains how to calculate the packing density within a Face-Centered Cubic (FCC) crystal lattice, arriving at approximately 74048% [2] - Boundary effects become significant in small containers or when the sphere radius is large, invalidating the 74% packing efficiency assumption [2][3] Higher Dimensions - Sphere packing efficiency decreases drastically as the number of dimensions increases, a phenomenon known as the "curse of dimensionality" [3] - Understanding high-dimensional spaces involves techniques like projection and "slicing" to visualize and analyze sphere packing [3]
特斯拉Ashok ICCV'25讲FSD与QA|952字压缩版/完整图文/完整视频
理想TOP2· 2025-10-23 15:33
Core Viewpoint - Tesla is shifting to a single, large end-to-end neural network that directly generates control actions from pixel and sensor data, eliminating explicit perception modules [1][34]. Group 1: Reasons for Transition to End-to-End Neural Networks - Integrating human values (like driving smoothness and risk assessment) into code is extremely challenging [3]. - Poor interface definitions between traditional perception, prediction, and planning can lead to information loss [4]. - The end-to-end approach is easier to scale for handling long-tail problems in the real world [5]. - It allows for homogeneous computation with deterministic latency, which is crucial for real-time systems [6]. Group 2: Challenges in Learning "Pixel to Control" - The primary challenges include the curse of dimensionality, interpretability and safety guarantees, and evaluation [7][8][9]. - The input context can be extensive, with a 30-second window potentially reaching 2 billion tokens [10][49]. - Tesla leverages its vast fleet data to extract valuable corner case data through complex, trigger-based data collection methods [11][51][56]. Group 3: Solutions to Challenges - For the curse of dimensionality, Tesla refines its extensive driving data to ensure the right correlations are captured [51][56]. - Interpretability is addressed by prompting the end-to-end model to predict various auxiliary outputs for debugging and safety assurance [12][60]. - Evaluation challenges are tackled by creating a neural network-based world simulator that can generate consistent video streams from multiple cameras [19][79]. Group 4: Future Developments - The next step involves the Cyber Cab, a next-generation vehicle designed specifically for robotaxi services, utilizing the same neural network technology [25][83]. - The technology developed for autonomous driving is also being adapted for humanoid robots, such as Optimus [26][86].
美军项目折戟,中国科学家却打破“魔咒”
Guan Cha Zhe Wang· 2025-07-24 03:51
Core Viewpoint - A revolutionary software design developed by a Chinese research team is set to overcome significant challenges in stealth aircraft development, enabling designers to increase design variables without raising computational load, thus addressing the "curse of dimensionality" in aerodynamics optimization [1][4]. Group 1: Software Innovation - The new platform allows for large-scale aerodynamic stealth optimization by enabling the addition of design variables while maintaining manageable computational complexity [1][4]. - The research team demonstrated the software's capabilities using the U.S. Navy's X47B stealth drone, achieving significant reductions in drag and radar cross-section (RCS) while improving total pressure recovery [1][3]. Group 2: Technical Details - The team improved 740 design variables, focusing on reducing flight resistance and radar detectability while ensuring engine thrust stability [3][4]. - A new geometric sensitivity calculation method was introduced, which decouples the cost of gradient calculations from the number of design variables, enhancing optimization efficiency [4]. Group 3: Industry Context - The U.S. is facing challenges with its Next Generation Air Dominance (NGAD) project, which may be delayed, while China is advancing its stealth aircraft capabilities [6]. - The new software could save significant time and resources for China's defense sector, providing critical support for the development of low-detectability aircraft amid rising global defense budgets [6][4].