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A statistical method for model extraction and model selection applied to the temperature scaling of the L–H transition

机译:一种统计方法,用于模型提取和模型选择,应用于L–H跃迁的温度换算

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摘要

Access to the H mode of confinement in tokamaks is characterized by an abrupt transition, which has been the subject of continuous investigation for decades. Various theoretical models have been developed and multi-machine databases of experimental data have been collected. In this paper, a new methodology is reviewed for the investigation of the scaling laws for the temperature threshold to access the H mode. The approach is based on symbolic regression via genetic programming and allows first the extraction of the most statistically reliable models from the available experimental data. Nonlinear fitting is then applied to the mathematical expressions found by symbolic regression; this second step permits to easily compare the quality of the data-driven scalings with the most widely accepted theoretical models. The application of a complete set of statistical indicators shows that the data-driven scaling laws are qualitatively better than the theoretical models. The main limitations of the theoretical models are that they are all expressed as power laws, which are too rigid to fit the available experimental data and to extrapolate to ITER. The proposed method is absolutely general and can be applied to the extraction or scaling law from any experimental database of sufficient statistical relevance.
机译:进入托卡马克禁闭区的H模式的特点是突然过渡,数十年来一直是不断研究的主题。已经开发了各种理论模型,并已收集了实验数据的多机数据库。在本文中,审查了一种新的方法,用于研究进入H模式的温度阈值的缩放定律。该方法基于通过遗传编程进行的符号回归,并且首先允许从可用的实验数据中提取统计上最可靠的模型。然后将非线性拟合应用于通过符号回归找到的数学表达式;第二步可以轻松地将数据驱动缩放的质量与最广泛接受的理论模型进行比较。一套完整的统计指标的应用表明,数据驱动的定标定律在质量上优于理论模型。理论模型的主要局限性在于它们都被表示为幂定律,这些定律过于僵化以至于无法拟合可用的实验数据并无法推断出ITER。所提出的方法是绝对通用的,并且可以应用于从具有足够统计相关性的任何实验数据库中提取或缩放定律。

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