用神经网络快速定位核泄漏源并量化不确定性,比传统方法快得多。
Rapid Parameter Inference with Uncertainty Quantification for a Radiological Plume Source Identification Problem
- 用分类神经网络划分区域预测源位置概率
- 贝叶斯神经网络通过权重采样生成参数后验分布
- 计算成本远低于马尔可夫链蒙特卡洛方法,适合应急响应
核事故或放射性装置爆炸后,快速定位污染源对应急响应和环境清理至关重要。在模拟瞬时释放放射性气溶胶后特定时间,利用下风向辐射传感器阵列的测量数据,结合平均风速信息,采用神经网络快速准确推断源释放参数。本文对比两种可量化不确定性的神经网络:分类神经网络将空间划分为若干区域,分别估计各区域包含真实源位置的概率;贝叶斯神经网络则赋予权重和偏置以分布,每次评估通过采样获得不同预测,训练后可构建释放参数的后验密度。结果与使用延迟拒绝自适应元蒙特卡洛算法(DRAM)得到的MCMC结果对比,贝叶斯神经网络在计算成本上显著更低,仅依赖神经网络评估开销,而非依赖传输与探测模型的高耗时计算。
原文摘要 · Abstract (English)
In the event of a nuclear accident, or the detonation of a radiological dispersal device, quickly locating the source of the accident or blast is important for emergency response and environmental decontamination. At a specified time after a simulated instantaneous release of an aerosolized radioactive contaminant, measurements are recorded downwind from an array of radiation sensors. Neural networks are employed to infer the source release parameters in an accurate and rapid manner using sensor and mean wind speed data. We consider two neural network constructions that quantify the uncertainty of the predicted values; a categorical classification neural network and a Bayesian neural network. With the categorical classification neural network, we partition the spatial domain and treat each partition as a separate class for which we estimate the probability that it contains the true source location. In a Bayesian neural network, the weights and biases have a distribution rather than a single optimal value. With each evaluation, these distributions are sampled, yielding a different prediction with each evaluation. The trained Bayesian neural network is thus evaluated to construct posterior densities for the release parameters. Results are compared to Markov chain Monte Carlo (MCMC) results found using the Delayed Rejection Adaptive Metropolis Algorithm. The Bayesian neural network approach is generally much cheaper computationally than the MCMC approach as it relies on the computational cost of the neural network evaluation to generate posterior densities as opposed to the MCMC approach which depends on the computational expense of the transport and radiation detection models.
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