The first wall of the fusion reactor is a plasma-facing component and is a key link to maintain the integrity of structure during thermal shock induced by plasma disruptions. Be and W/Cu functionally graded materials ...The first wall of the fusion reactor is a plasma-facing component and is a key link to maintain the integrity of structure during thermal shock induced by plasma disruptions. Be and W/Cu functionally graded materials are two kinds of important plas- ma-facing materials （PFM） of first wall in fusion reactor currently. Previous researches seldom comparatively evaluated the normal servicing and heat shock resistance performance of first walls with those two kinds of PFMs. And also there lacks cou- pled thermal/mechanical analysis on the heat shock process in consideration of multiple thermal/mechanical phenomena, such as material melting, solidification, evaporation, etc., which is significant to further understand the heat shock damage mecha- nism of the first wall with different PFMs. With the aim of learning more detailed mechanical mechanism of thermal shock damage and then improving the thermal shock resistance performance of different first wall designs, the coupled ther- mal/mechanical response of two typical ITER-like first walls with PFM of Be and functionally graded W-Cu respectively un- der the heat shock of 1 2 GW/m2 are computed by the finite element method. Special considerations of elastic-plastic defor- mation, material melting, and solidification are included in numerical models and methods. The mechanical response behaviors of different structures and materials under the normal servicing operation as well as plasma disruption conditions are analyzed and investigated comparatively. The results reveal that heat is mainly deposited on the PFM layer in thc high energy shock pulse induced by plasma disruptions, resulting in complex thermal stress change as well as mechanical itTeversible damage of thermal elastic and plastic expansion, contraction and yielding. Compared with the first wall with Be PFM, which mitigates the damages from heat shock at most only in the PFM layer with cost of whole PFM layer plastic yielding, the first wall with graded W-Cu PFM is demonstrated to be possessed both of higher heat shock resistance performance and normal servicing performance, provided its material gradient and cooling capacity are well optimized under practical loading conditions.展开更多
Synchronization behavior of an ensemble of unidirectionally coupled neurons with a constant input is investigated. Chemical synapses are considered for coupling. Each neuron is also considered to be exposed to a self-...Synchronization behavior of an ensemble of unidirectionally coupled neurons with a constant input is investigated. Chemical synapses are considered for coupling. Each neuron is also considered to be exposed to a self-delayed feedback. The synchronization phenomenon is analyzed by the error dynamics of the response trajectories of the system. The effect of various model parameters e.g. coupling strength, feedback gain and time delay, on synchronization is also investigated and a measure of synchrony is computed in each cases. It is shown that the synchronization is not only achieved by increasing the coupling strength, the system also required to have a suitable feedback gain and time delay for synchrony. Robustness of the parameters for synchrony is verified for larger systems.展开更多
基金supported by the National Magnetic Confinement Fusion Science Program of China(Grant Nos.2015GB121007&2013GB113004)
文摘The first wall of the fusion reactor is a plasma-facing component and is a key link to maintain the integrity of structure during thermal shock induced by plasma disruptions. Be and W/Cu functionally graded materials are two kinds of important plas- ma-facing materials （PFM） of first wall in fusion reactor currently. Previous researches seldom comparatively evaluated the normal servicing and heat shock resistance performance of first walls with those two kinds of PFMs. And also there lacks cou- pled thermal/mechanical analysis on the heat shock process in consideration of multiple thermal/mechanical phenomena, such as material melting, solidification, evaporation, etc., which is significant to further understand the heat shock damage mecha- nism of the first wall with different PFMs. With the aim of learning more detailed mechanical mechanism of thermal shock damage and then improving the thermal shock resistance performance of different first wall designs, the coupled ther- mal/mechanical response of two typical ITER-like first walls with PFM of Be and functionally graded W-Cu respectively un- der the heat shock of 1 2 GW/m2 are computed by the finite element method. Special considerations of elastic-plastic defor- mation, material melting, and solidification are included in numerical models and methods. The mechanical response behaviors of different structures and materials under the normal servicing operation as well as plasma disruption conditions are analyzed and investigated comparatively. The results reveal that heat is mainly deposited on the PFM layer in thc high energy shock pulse induced by plasma disruptions, resulting in complex thermal stress change as well as mechanical itTeversible damage of thermal elastic and plastic expansion, contraction and yielding. Compared with the first wall with Be PFM, which mitigates the damages from heat shock at most only in the PFM layer with cost of whole PFM layer plastic yielding, the first wall with graded W-Cu PFM is demonstrated to be possessed both of higher heat shock resistance performance and normal servicing performance, provided its material gradient and cooling capacity are well optimized under practical loading conditions.
文摘Synchronization behavior of an ensemble of unidirectionally coupled neurons with a constant input is investigated. Chemical synapses are considered for coupling. Each neuron is also considered to be exposed to a self-delayed feedback. The synchronization phenomenon is analyzed by the error dynamics of the response trajectories of the system. The effect of various model parameters e.g. coupling strength, feedback gain and time delay, on synchronization is also investigated and a measure of synchrony is computed in each cases. It is shown that the synchronization is not only achieved by increasing the coupling strength, the system also required to have a suitable feedback gain and time delay for synchrony. Robustness of the parameters for synchrony is verified for larger systems.
