Deep learning approaches to recover the plasma current density profile from the safety factor based on Grad–Shafranov solutions across multiple tokamaks

Many magnetohydrodynamic stability analyses require generation of a set of equilibria with a fixed safety factor q-profile while varying other plasma parameters.A neural network(NN)-based approach is investigated that facilitates such a process.Both multilayer perceptron(MLP)-based NN and convolutional neural network(CNN)models are trained to map the q-profile to the plasma current density J-profile,and vice versa,while satisfying the Grad–Shafranov radial force balance constraint.When the initial target models are trained,using a database of semianalytically constructed numerical equilibria,an initial CNN with one convolutional layer is found to perform better than an initial MLP model.In particular,a trained initial CNN model can also predict the q-or J-profile for experimental tokamak equilibria.The performance of both initial target models is further improved by fine-tuning the training database,i.e.by adding realistic experimental equilibria with Gaussian noise.The fine-tuned target models,referred to as fine-tuned MLP and fine-tuned CNN,well reproduce the target q-or J-profile across multiple tokamak devices.As an important application,these NN-based equilibrium profile convertors can be utilized to provide a good initial guess for iterative equilibrium solvers,where the desired input quantity is the safety factor instead of the plasma current density.

Loss of energetic particles due to feedback control of resistive wall mode in HL-3

Effects of three-dimensional(3D)magnetic field perturbations due to feedback control of an unstable n=1(n is toroidal mode number)resistive wall mode(RWM)on the energetic particle(EP)losses are systematically investigated for the HL-3 tokamak.The MARS-F(Liu et al 2000 Phys.Plasmas 73681)code,facilitated by the test particle guiding center tracing module REORBIT,is utilized for the study.The RWM is found to generally produce no EP loss for cocurrent particles in HL-3.Assuming the same perturbation level at the sensor location for the close-loop system,feedback produces nearly the same loss of counter-current EPs compared to the open-loop case.Assuming however that the sensor signal is ten times smaller in the close-loop system than the open-loop counter part(reflecting the fact that the RWM is more stable with feedback),the counter-current EP loss is found significantly reduced in the former.Most of EP losses occur only for particles launched close to the plasma edge,while particles launched further away from the plasma boundary experience much less loss.The strike points of lost EPs on the HL-3 limiting surface become more scattered for particles launched closer to the plasma boundary.Taking into account the full gyro-orbit of particles while approaching the limiting surface,REORBIT finds slightly enhanced loss fraction.

Effect of ideal internal MHD instabilities on NBI fast ion redistribution in ITER 15 MA scenario

Transport of fast ions is a crucial issue during the operation of ITER.Redistribution of neutral beam injection(NBI)fast ions by the ideal internal magnetohydrodynamic(MHD)instabilities in ITER is studied utilizing the guiding-center code ORBIT(White R B and Chance M S 1984Phys.Fluids 272455).Effects of the perturbation amplitude A of the internal kink,the perturbation frequency f of the fishbone instability,and the toroidal mode number n of the internal kink are investigated,respectively,in this work.The n=1 internal kink mode can cause NBI fast ions transporting in real space from regions of 0<s≤0.32 to 0.32<s≤0.53,where s labels the normalized plasma radial coordinate.The transport of fast ions is greater as the perturbation amplitude increases.The maximum relative change of the number of fast ions approaches 5%when the perturbation amplitude rises to 500 G.A strong transport is generated between the regions of 0<s≤0.05 and 0.05<s≤0.12 in the presence of the fishbone instability.Higher frequency results in greater transport,and the number of fast ions in 0<s≤0.05 is reduced by 30%at the fishbone frequency of 100 k Hz.Perturbations with higher n will lead to the excursion of fast ion transport regions outward along the radial direction.The loss of fast ions,however,is not affected by the internal MHD perturbation.Strong transport from 0<s≤0.05 to 0.05<s≤0.12 does not influence the plasma heating power of ITER,since the NBI fast ions are still located in the plasma core.On the other hand,the influence of fast ion transport from 0<s≤0.32 to 0.32<s≤0.53 needs further study.

Comparison of clinical outcomes of Chinese men and women after coronary stenting for coronary artery disease:a multi-center retrospective analysis of 4,334 patients

The outcome differences between Chinese male and female patients within one-year follow-up after percutaneous coronary intervention（PCI） with stent remain unclear.The present study was aimed to compare clinical outcomes in such two populations.From May 1999 to December 2009,4,334 patients with acute myocardial infarction（MI）,unstable angina,stable angina,or silent ischemia,who underwent PCI,were registered at our centers.Among these,3,089 were men and 1,245 were women.We compared these groups with respect to the primary outcomes of MI and secondary outcomes including a composite of major adverse cardiac events（MACE） including cardiac death,MI,target lesion revascularization,target vessel revascularization（TVR）,stent thrombosis（ST）,definite ST and probable ST at one-year follow-up.Chinese male patients had a higher MACE rate（13%vs.10.7%,P =0.039）,mainly led by TVR（9.09%vs.6.98%,P=0.024） at one year,which was significantly different than female patients.Chinese male and female patients showed a significant difference on MACEs.However,there was no significant difference with respect to MI between these groups.

Modifying regeneration strategies classification to enhance the understanding of dominant species growth in fire-prone forest in Southwest China

Background:In fire-prone ecosystems,plant species having different post-fire regeneration strategies(PFRS)coexist at the local scale while showing different growth dynamics.To evaluate the effect of PFRS on species regeneration,we investigated the plant communities burned in different years in the central Yunnan Province,Southwest China.Several indicators describing plant growth and population importance were measured to compare the regeneration of four dominant tree species,including one facultative seeders(FS)and three obligate resprouters(OR).Partial correlation and mixed linear effect modeling were applied to disentangle the contribution of intrinsic and environmental factors to the interspecific variation in post-fire regeneration.Results:We identified two subtypes of plant growth strategy in the early post-fire stage for OR species;i.e.,number growth(ORþN)priority and height growth(ORþH)priority for sprouting stems.Generally,the FS and OR species varied in height growth rate with different temporal dynamics.The ORþN species occupied post-fire space horizontally with more resprouts and larger coverage than ORþH and FS species at the earlier stage.In contrast,the ORþH species generally had far less resprouts per clump,more variations in stem height and basal diameter.Factor analysis showed that the variation of post-fire plant regeneration was not effectively explained by environmental factors(R2<20%);however,the linear mixed models with the modified PFRS as a random effect substantially increased the explanation.Conclusions:The differentiated regeneration dynamics and growth priorities in the four dominant tree species indicated a critical dichotomy of habitat occupation strategy for the resprouter species during the early stage of post-fire forest restoration.Our study uncovered a trade-off between height versus number growth priority in the post-fire tree growth strategy and provides a novel perspective in understanding the living space occupying(niche partitioning)process and species coexistence in post-fire forest community assembly.

Effect of single-legged coil on 3D plasma boundary corrugation in EAST

A single-legged coil behind the lower divertor and covering a 120° toroidal angle is utilized in a recent EAST discharge, for the purpose of increasing the wetted area of the divertor surface by locally modifying the magnetic field near the X-point. The plasma response, in particular, the plasma boundary surface corrugation due to the single-legged coil current, is modeled by the updated MARS-F code, by computing the plasma displacement for all important toroidal harmonics(n?=?1, 2, 4 and 5) associated with the partial toroidal coverage by the coil. The plasma response produced by the single-legged coil is found to be non-local and is of the kinkpeeling type. For a reference EAST plasma with a lower single-null magnetic configuration, the plasma boundary corrugation near the X-point, produced by the upper single-legged coil, is about twice as large as that produced by the lower single-legged coil, despite the proximity of the latter to the X-point.

The Impact of Incentives on the Number of Suppliers

In the context of adulteration by suppliers,downstream firms need to choose between incentives and regulation to ensure product quality.Studies have shown that the adulteration behavior of suppliers increases with the degree of dispersion of suppliers,that is,the number of suppliers increases.Therefore,based on the assumption that the number of suppliers impacts quality uncertainty,this paper further introduces the number of suppliers into the incentive model to investigate the relationship between supply chain dispersion,that is,the number of suppliers,social integrity,and incentive strength.The study finds that the optimal number of suppliers depends on social integrity,regulatory cost,and incentive strength.There is a positive correlation between social integrity and the number of suppliers,while regulatory costs and incentive strength have a negative correlation with the number of suppliers.That means,the higher the social integrity,the lower the regulatory cost;and the lower the incentive intensity,the more optimal suppliers can be selected.