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1 Primary & Middle School Mathematics1–9 年级在线 2 High School Mathematics10–12 年级在线 3 University Mathematics — Year 1本科一年级在线 4 University Mathematics — Year 2本科二年级在线 5 University Mathematics — Year 3本科三年级在线

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1 Markets I: The Ecosystem and Exchange-Traded Markets市场在线 2 Markets II: Rates, FX and Credit市场在线 3 Markets III: Commodities, Energy and Crypto市场在线 4 Quantitative Methods方法在线 5 Derivatives and Volatility衍生品在线 6 Rates, Credit, XVA and Risk利率、信用与风险在线 7 Research Craft: Predictors, Backtests, Measurement, Portfolios研究在线 8 Strategies I: Equities and Futures策略在线 9 Strategies II: Volatility, Relative Value, Macro and the Bank Desks策略在线 10 Microstructure and Execution交易执行在线 11 Market Making and High-Frequency Trading做市在线 12 Machine Learning for Markets机器学习在线 13 Low-Latency Software技术在线 14 Networks, Hardware and Trading Infrastructure技术在线 15 Research, Data and Risk Platforms技术在线 16 The Desk and the Firm公司运营在线 17 The Industry: Firms, Roles and Careers职业发展在线 18 Interviews I: Maths, Probability and Speed职业发展在线 19 Interviews II: Markets, Trading Games and the Final Round职业发展在线 20 Interviews III: Code职业发展在线

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Earth and Space Sciences · 术语表

什么是 Fission-track dating, track annealing？

又称： fission-track dating · track annealing

Definition 13.8 University Earth and Space Sciences — Year 3 · 第 13 章 — Advanced Geochronology

Fission-track dating dates a mineral by the density of the tracks left in it by the spontaneous fission of uranium-238, compared with its uranium content. Track annealing is the shortening and disappearance of the tracks by repair of the crystal when it is heated.

Schematic. (a) Spontaneous fission tracks, revealed by etching on a polished apatite grain, are counted per unit area. (b) An alpha particle travels about 20\, µ m: those emitted within that distance of the surface (outside the dashed line) may leave the grain, so a small grain keeps less of its helium. — Schematic. (a) Spontaneous fission tracks, revealed by etching on a polished apatite grain, are counted per unit area. (b) An alpha particle travels about $20\,\text{µ}\mathrm{m}$ : those emitted within that distance of the surface (outside the dashed line) may leave the grain, so a small grain keeps less of its helium.

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