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[en] This Ph. D. work is motivated by the possibility of monitoring the conditions of components of energy systems for their extended and safe use, under proper practice of operation and adequate policies of maintenance. The aim is to develop a Support Vector Regression (SVR)-based framework for predicting time series data under stationary/nonstationary environmental and operational conditions. Single SVR and SVR-based ensemble approaches are developed to tackle the prediction problem based on both small and large datasets. Strategies are proposed for adaptively updating the single SVR and SVR-based ensemble models in the existence of pattern drifts. Comparisons with other online learning approaches for kernel-based modelling are provided with reference to time series data from a critical component in Nuclear Power Plants (NPPs) provided by Electricite de France (EDF). The results show that the proposed approaches achieve comparable prediction results, considering the Mean Squared Error (MSE) and Mean Relative Error (MRE), in much less computation time. Furthermore, by analyzing the geometrical meaning of the Feature Vector Selection (FVS) method proposed in the literature, a novel geometrically interpretable kernel method, named Reduced Rank Kernel Ridge Regression-II (RRKRR-II), is proposed to describe the linear relations between a predicted value and the predicted values of the Feature Vectors (FVs) selected by FVS. Comparisons with several kernel methods on a number of public datasets prove the good prediction accuracy and the easy-of-tuning of the hyper-parameters of RRKRR-II. (author)
[en] Aquatic environments are increasingly under environmental stress due to ultraviolet (UV) radiation and potential inputs of nanoparticles with intense application of nanotechnology. In this study, we investigated the interaction between UV-B radiation and titanium nanoparticles (TiO2-NPs) in a model freshwater cladoceran Daphnia magna. UV-B toxicity to Daphnia magna was examined when the daphnids were exposed to a range of TiO2-NPs concentrations with an initial 5 or 10 min of 200 μW/cm2 UV-B radiation. In addition, UV-B toxicity was also examined in the presence of TiO2-NPs in the body of daphnids. Our results demonstrated that the daphnid mortality under UV-B radiation decreased significantly in the presence of TiO2-NPs both in the water and in the body, indicating that TiO2-NPs had some protective effects on D. magna against UV-B. Such protective effect was mainly caused by the blockage of UV-B by TiO2-NPs adsorption. UV-B produced reactive oxygen species (ROS) in the water and in the daphnids, which was not sufficient to cause mortality of daphnids over short periods of radiation. Previous studies focused on the effects of TiO2-NPs on the toxicity of total UV radiation, and did not attempt to differentiate the potential diverse roles of UV-A and UV-B. Our study indicated that TiO2-NPs may conversely protect the UV-B toxicity to daphnids. - Highlights: • Interaction between UVB radiation and TiO2-NPs was studied in Daphnia magna. • Daphnid mortality under UVB decreased in the presence of TiO2-NPs both in the water and in the body. • Reactive oxygen species produced by UVB was not sufficient to cause mortality of daphnids. • TiO2-NPs may protect the UVB toxicity to daphnids.
[en] This paper gives a general description of functions, usages and system configurations of the instruments and their major units or components of the radiation monitoring system, as well as the status and technical gap between domestic and foreign technologies. And then the paper also puts forward an idea on product R and D, i.e. combination of independent R and D and innovation, assimilation and re-innovation of foreign advanced technology at present situation in order to keep pace with the rapid development of nuclear power in China and achieve the goal of localization of nuclear power equipment. (authors)
[en] A computer code PROVER-II is developed for the propagation phase of a sodium vapor explosion. A new thermal fragmentation model is proposed that includes three kinds of timescales for modeling the instant fragmentation, spontaneous nucleation fragmentation, and normal boiling fragmentation. The pressure wave propagation in a sodium vapor explosion is analyzed and compared with that in a steam explosion. The energy conversion ratio of an in-vessel sodium vapor explosion is calculated by using hydrodynamic and thermal fragmentation mechanisms, and sensitivity analyses are carried out for some parameters. The initial thermal conditions for energetic fuel-coolant interactions in a sodium system are examined. Results show that the high saturation temperature of sodium results in a much lower pressure peak in a sodium vapor explosion compared to a steam explosion, and the mechanical energy release is limited by the mass of melt participating in the explosion during the core disruptive accident in liquid-metal-cooled fast breeder reactors
[en] A novel adaptive control method is proposed for controlling newly introduced uncertain unified system. The observer technique is applied to identify the unknown parameter of the unified system. Based on this observer, a simple controller is designed via extending equilibrium manifolds of the original system, which can stabilize the chaotic irregular states not only to arbitrary desired equilibrium-alike points but also to any target periodic orbits as designated online. Numerical simulations are provided to show the effectiveness of the proposed control method