Physical design of a new set of high poloidal mode number coils in the EAST tokamak

An external resonant magnetic perturbation (RMP) field, an effective method to mitigate or suppress the edge localized mode (ELM), has been planned to be applied on the ELM control issue in ITER. A new set of magnetic perturbation coils, named as high m coils, has been developed for the EAST tokamak. The magnetic perturbation field of the high m coils is localized in the midplane of the low field side (LFS), with a spectrum characteristic of high m and wide n, where m and n are the poloidal and toroidal mode numbers, respectively. The high m coils generates a strong localized perturbation field. Edge magnetic topology under the application of high m coils should have either a small or no stochastic region. With the combination of the high m coils and the current RMP coils, flexible working scenarios of the magnetic perturbation field are available, which is beneficial for ELM control exploration on EAST. Numerical simulations have been carried out to characterize the high m coil system, including the magnetic spectrum and magnetic topology, which shows a great flexibility of magnetic perturbation variation as a tool to investigate the interaction between ELM and external magnetic perturbation.

An Assimilation Simulation Approach to Suspended Sediment Concentration in Inland Lakes Using Hybrid Perturbation Generation Method

Suspended sediments, as one of the most important factors affecting the water environment of inland lakes, are closely related to the various pollutants migration and interaction. Thus, the simulation and prediction of suspended sediment concentration is important. Existing studies show that the prediction accuracy of suspended sediment concentration can be effective predicted based on assimilation methods coupled with hydrodynamic models. However, in the process of assimilation of hydrological simulation, the existing perturbation generation methods consider that the perturbation error is a random Gaussian distribution, which does not consider the spatial variation characteristics of errors. In this paper, a new method to generate the perturbation field for assimilation simulation was proposed. This method uses hybrid error to generate perturbation field for assimilation simulation instead of using random error. The proposed approach was validated through its application to assimilation simulation of suspended sediment concentration of Taihu Lake in China, and five assimilation experiments was conducted. The proposed method was compared with existing methods for perturbation field generation. After three days and 72 time steps of assimilation simulation based on hybrid perturbation generation, we found that the proposed assimilation method provided results that were more consistent with buoy-measured data. The accuracy of the two assimilation methods based on hybrid perturbation is improved. Compared with the assimilation method based on random perturbation, the mean values of RMSE(root mean square error) decreased from 9.56 to 8.70 and from 9.55 to 8.68, respectively. The results show that the proposed hybrid perturbation generation method has higher simulation accuracy than other methods. This study shows that the method is effective and provides a new idea for the assimilation simulation of suspended sediment concentration in inland lakes.

Analysis of Heat Transfer in Particle Velocity Sensor with Three-Wire Configuration

Particle velocity sensor (PVS) plays an important role in determining the type and location of a sound source. In this presentation, analytical model of heat transfer in PVS with a three-wire (SHS) configuration was first presented. By comparing with the thermal diffusion motion, the forced convection exerts a smaller influence on the temperature distribution. Thus, variation in forced convection could induce the formation of a thermal perturbation field. The overall temperature distribution model of a PVS is made up of a steady temperature field and a thermal perturbation field. With the derived model, PVS with SHS configuration has smaller thermal noise and higher signal-to-noise ratio in comparision with a two-wire (SS) configuration under the same conditions. Optimized parameters of structure design and heating power could be obtained via the analysis model. Also, this model gives optimal output performance and frequency-dependent characteristic curve. Numerical results are found to be in good agreement with the analytical solutions and experimental data, which verify the correctness of analytical model and numerical method. The study provides a basis for a theoretical and numerical analysis.

Increased speech contrast induced by sensorimotor adaptation to a non-uniform auditory perturbation

When auditory feedback is perturbed in a consistent way, speakers learn to adjust their speech to compensate, a process known as sensorimotor adaptation. While this paradigm has been highly informative in understanding speech sensorimotor control, its ability to induce behaviorally-relevant changes in speech that affect communication effectiveness remains unclear. Here, we examine human speakers’ ability to compensate for a non-uniform perturbation field which reduces vowel distinctiveness by shifting all vowels toward the center of vowel space. Speakers adapted to this non-uniform shift, learning to produce corner vowels with increased vowel space area and vowel contrast to partially overcome the apparent centralization. The increase in vowel contrast occurred without a concomitant increase in duration and persisted after the feedback shift was removed, including after a 10-minute silent period. These findings establish the validity of a sensorimotor adaptation paradigm to increase vowel contrast, an outcome that has the potential to enhance intelligibility.

One Inclusion in the Infinite Peristatic Matrix

A basic problem of of micromechanics is analysis of one inclusion in the infinite matrix subjected to a homogeneous remote loading. A heterogeneous medium with the bond-based peri-dynamic properties (see Silling, J. Mech. Phys. Solids 2000; 48:175–209) of constituents is considered. At first a volumetric boundary conditions are set up at the external boundary of a final domain obtained from the original infinite domain by truncation. An alternative sort of truncation method is periodisation method when a unite cell (UC) size is increased while the inclusion size is fixed. In the second approach, the displacement field is decomposed as linear displacement corresponding to the homogeneous loading of the infinite homogeneous medium and a perturbation field introduced by one inclusion. This perturbation field is found by the Green function technique as well as by the iteration method for entirely infinite sample with an initial approximation given by a driving term which has a compact support. The methods are demonstrated by numerical examples for 1D case. A convergence of numerical results for the peristatic composite bar to the corresponding exact evaluation for the local elastic theory are shown.