In this paper, an overview of the magnetohydrodynamic instabilities induced by energetic electrons on HL-2A is given and some new phenomena with high-power electron cyclotron resonance heating (ECRH) are presented. A toroidal Alfvén eigenmode with frequency from 200 to 350 kHz is identified during powerful ECRH. In the lower frequency range from 10 to 35 kHz, which is in the beta-induced Alfvén eigenmode frequency range, the coexistence of multi-mode is found during the high-power ECRH for the first time. The spectra become wide when the power is sufficiently high. The frequencies of the modes increase with and are much lower than the Alfvén frequency. The relationship between the mode frequency and (7/4 + Te/Ti)1/2 (Ti)1/2 can be obtained by statistical data analysis. Between the two previous frequency ranges, a group of new modes with frequencies from 50 to 180 kHz is observed with high-power ECRH and neutral beam injection heating together. The modes have clear frequency chirping within several milliseconds or several tens of milliseconds, which are identified as energetic particle mode like instabilities. The new features of the fishbone instability excited by energetic electrons are identified. It is interesting to find the frequency jump phenomena in the high-power ECRH. The difference between the low and high frequencies increases with ECRH power. The frequency jumps between 8 and 15 kHz within about 25 ms periodically, when the power is 1.2 MW.
PurposePrefabricated construction concerns off-site production, multi-mode transportation and on-site installation of the prefabricated components, which are interdependent and dynamically interactive, so coordination among the multiple stages along the prefabricated component supply chain (PCSC) is indispensable. This study aims to solve the dynamic transportation planning problem for the PCSC by addressing the interdependency, dynamic interaction and coordination among the multiple stages and different objectives of the stakeholders.Design/methodology/approachThe PCSC is analyzed and then the formulation for the dynamic transportation planning problem is developed based on the just-in-time (JIT) strategy. The particle swarm optimization (PSO) algorithm is applied to solve the dynamic optimization problem.FindingsThe proposed dynamic transportation planning method for the PCSC regarding component supplier selection, transportation planning for means, routes and schedule, site layout planning and transportation plan adjustment is able to facilitate coordination among the multiple stages by addressing their interdependencies and dynamic interactions, as well as different economic objectives of the stakeholders such as suppliers or the contractor.Originality/valueThe study helps to achieve the advantages of prefabricated construction by prompting coordination among multiple stages of the PCSC by realizing different benefits of the stakeholders. In addition, it provides the stakeholders with the competitive bidding prices and the evaluation data for the bids quote. Meanwhile, it contributes to the domain knowledge of the PCSC management with regard to the viewpoint of coordination and integration of multiple stages rather than only one stage as well as the dynamic optimization model based on the JIT strategy and the PSO algorithm.
Summary To enhance the resilience of distribution systems and fight against extreme disasters, a novel planning‐attack‐reconfiguration optimization method is proposed in this paper. Firstly, according to the processes of prevention, defence, and restoration for a resilient distribution system through disruption, the novel resilience evaluation indicators are presented, which include the node degree of distributed generation (DG) bus, survival rate, and recovery ability. Secondly, a novel planning‐attack‐reconfiguration optimization model is developed to improve the resilience of distribution systems. In DG planning stage, the multi‐objective planning model is formulated, which includes the minimization of the total cost of investment and operation, and the maximization of the node degree of DG buses for critical loads. In the attack stage, a clear worst case of N‐k contingencies on the basis of generalized nodes is presented to reduce the computational complexity. Then, the post‐disaster network reconfiguration model is formulated to maximize the restoration rate of critical loads (RRCL). Finally, the proposed method is illustrated by the case study on PG&E 69‐bus distribution system. The simulation results indicate that all the RRCL can reach about 90% in the four multipoint fault scenarios. Meanwhile, other evaluation indicators are greatly improved. It is shown that the resilience of distribution systems can be dramatically enhanced by the proposed method.
Research on beta induced Alfvén eigenmodes (BAEs) driven by energetic ions has been carried out on the HL2A tokamak. The BAEs can be observed in the cases of q min being beyond or below unity. The mode frequencies are around 60-95 kHz. The radial mode structures have been detected by the multichannel microwave reflectometer and soft xray arrays. The results suggest that the BAEs are highly localized at the normalized radius of ρ = 0.07-0.26. Theoretical analyses based on the general fishbonelike dispersion relation and Alfvén mode code support the experimental measurements in both mode frequencies and locations. The BAEs are found to be excited more easily in low electron density discharges. The coexistence of BAEs and reversed shear Alfvén eigenmodes enables the estimation of q min directly from experiments.
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