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Novel view synthesis using implicit neural functions such as Neural Radiance Field (NeRF) has achieved significant progress recently. However, it is very computationally expensive to train a NeRF due to the disordered frequency optimization. In this paper, we propose the Pyramid NeRF, which guides the NeRF training in a 'low-frequency first, high-frequency second' style using the image pyramids and could improve the training and inference speed at 15 × and 805 × , respectively. The high training efficiency is guaranteed by (i) organized frequency-guided optimization could improve the convergency speed and efficiently reduce the training iterations and (ii) progressive subdivision, which replaces a single large multi-layer perceptron (MLP) with thousands of tiny MLPs, could significantly decrease the execution time of running MLPs. Experiments on various synthetic and real scenes verify the high efficiency of the Pyramid NeRF. Meanwhile, the structure and perceptual similarities could be better recovered. [ABSTRACT FROM AUTHOR]

While reservoir dams have created significant social and economic benefits, dam failure caused by various reasons bring about great threats to the downstream areas. Many countries determine management investment according to the risk level of reservoir dams and the "as low as reasonably practicable" (ALARP) principle. However, life cannot be directly quantified in currency, and the traditional "cost-benefit" method cannot be effectively applied to reservoir dam management decisions. Hence, the life quality index (LQI) was introduced and improved to solve this problem based on the targeted analysis of the parameters of the life quality index, considering the fact that the per capita GDP changes over time. Without monetary quantification of life, an annual economic investment was determined to effectively control the risk level of the reservoir dam in a certain period of time in the future to ensure people's life safety and quality of life. The improved LQI method was applied to a small-scale reservoir in China. The results showed that (a) the annual investment in dam risk management calculated by the improved LQI method was 20.07% higher than that of the traditional LQI method; (b) the annual investment in dam management changed 24 times due to changes in warning time and public risk awareness; and (c) dam management investment should be used not only to ensure the safety of the structure but also to improve early warning capacity and public risk awareness. This study focuses on how to reasonably determine the management investment of reservoir dams when the dam risk is in the ALARP region, which can effectively promote the application of dam risk standards. [ABSTRACT FROM AUTHOR]