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Copper's Surprising Melting Behavior Provides Insights for Future Fusion Power Plant Design

2 weeks 6 days ago
Phys.org reports: Future fusion power plants aim to recreate the heart of a star here on Earth to power our future energy needs. While the core fusion plasma will burn at hundreds of millions of degrees, the surrounding structural components must handle sudden, punishing heat loads that rival the extreme temperatures faced by spacecraft upon reentry into Earth's atmosphere. Copper and its alloys are primary candidates for handling these intense heat fluctuations, making it vital to understand exactly how the metal behaves when pushed to its melting point. Now, researchers at the Department of Energy's SLAC National Accelerator Laboratory and collaborators have captured a detailed, step-by-step look at copper atoms as they underwent extreme heating. Published in Nature Communications, the results revealed a key parameter that allowed copper's crystal lattice to melt steadily rather than collapse instantaneously, as earlier simulations predicted. "These results greatly improve the simulations we use to predict which materials have the best shot at surviving the extreme conditions of future fusion reaction chambers," said Mianzhen Mo, a SLAC staff scientist who led the research. "They also demonstrate the incredible, atomic-scale resolution imaging we can achieve at SLAC's electron camera...." Researchers use computer simulations, aided by AI and machine learning, to sift through innumerable combinations of elements and identify promising candidate materials for real-world testing. "Whether the copper melts slowly or suddenly collapses, by the time the researchers look, the sample resembles nothing more than a metallic brown puddle," the article points out. But SLAC's powerful electron camera captures atomic and molecular movements down to the femtosecond — a millionth of a billionth of a second — and revealed that at around 1,424 degreesC (2,595 degreesF) there was still gradual melting as the temperature rose beyond the superheating limit, with real-world conditions showing the atoms shifted and retained some order. "It's a straightforward solution," said Mianzhen Mo, a SLAC staff scientist who led the research. "But molecular dynamics simulations had been overlooking it for years. When you have complex simulations attempting to capture every aspect of reality, down to individual atoms, it takes real-world data to show you what's missing from the calculations."

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EditorDavid

X Open Sources Its Ranking and Filtering Algorithms

3 weeks ago
An anonymous reader shared this report from TechCrunch: X is significantly expanding its open source codebase, which includes the app's "For You" algorithm and its core ranking engine, and adding a feature that will let users see if their account or posts have been impacted by any of its ranking systems, the social network said on Thursday. The company is making the source code for the "For You" timeline, the default feed you see when you open the app, available on GitHub under the Apache v2 license. It's also expanding its previous efforts to open source parts of its codebase to add more detail, including the model configuration, filter, and core ranking system details. That means it includes the parameters used to weight different signals — key to understanding which posts are actually displayed. This also makes the codebase roughly 10 to 15 times larger than it was before. "You'll get the core ranking code that pulls posts and ranks them for any given user and assembles the feed," X's VP of Product Keith Coleman told TechCrunch in an interview ahead of the announcement. "You can see the systems that filter out potentially problematic, rule-violating content...And some of those systems, like the ranker and the score, you can even run yourself outside the company." "This is the kind of thing that I think people will be fairly shocked that we are releasing," he added. In addition to the repository, X is providing tools that will let users see for themselves if and how X's ranking systems have impacted their account or posts. A new transparency tool is rolling out to an "Under the Hood" page in the app's settings, which will let users who have posted 10 or more times over the past month download their aggregate stats as a JSON file. The file will show if any labels have been applied to their account or posts over the past calendar month. X's VP of Product told TechCrunch that X engineers will consider pull requests. "That would be amazing to have people submitting code that improves the algorithm...I mean, how cool would it be for the X algorithm to be not just visible to the public, but also, like, by the public?"

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EditorDavid