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A new method of power feedback control for the lower hybrid wave (LHW) systems on the experimental advanced superconducting tokamak (EAST) is presented. Different methods are applied to control the power of two LHW systems with different frequency at 2.45 GHz and at 4.6 GHz, respectively. The old method is applied to control the 4.6 GHz LHW power through the exciter of klystrons, and the new one is used to control the 2.45 GHz LHW power through the high voltage power supply (HVPS) system. The new method has been applied in EAST and successfully assisted the development of relevant experiments such as loop voltage control, q profile control.

Biodiesel is a very promising alternative fuel in internal combustion engines. Fragmentation of the fuel injection has a fundamental influence on engine performance. The influence factors for the spray breakup process, including near nozzle fields, are still unclear. In this study, the primary of fuel sprays occurring with turbulence perturbation is devoted to simulation. The evolutionary processes of biodiesel fuels atomization affected by turbulence are investigated in present models. A validated single-phase fully developed turbulent flow is generated first to store time-varying outlet velocity database. Then, the database is mapped as the two-phase model inlet velocities boundary. A modified VOF (Volume of Fluid) coupled with DNS (direct numerical simulation) method is applied to study the evolution of fuel spray. It is found that wavy surface, ligaments, and droplets with various scales and shapes turn up gradually in jet evolution process. Meanwhile, after being sheared, distorted and stretched, different ligaments separation patterns are captured. Larger Reynolds number and higher gas densities accelerate the jet break-up process. Higher injection velocities and lower power-law indexes (n 1) fuel jet. What’s more, similar breakup patterns are detected in shear-thinning fluid (n

As the best substitute for antibiotics, antimicrobial peptides (AMPs) have important research significance. Due to the high cost and difficulty of experimental methods for identifying AMPs, more and more researches are focused on using computational methods to solve this problem. Most of the existing calculation methods can identify AMPs through the sequence itself, but there is still room for improvement in recognition accuracy, and there is a problem that the constructed model cannot be universal in each dataset. The pre-training strategy has been applied to many tasks in natural language processing (NLP) and has achieved gratifying results. It also has great application prospects in the field of AMP recognition and prediction. In this paper, we apply the pre-training strategy to the model training of AMP classifiers and propose a novel recognition algorithm. Our model is constructed based on the BERT model, pre-trained with the protein data from UniProt, and then fine-tuned and evaluated on six AMP datasets with large differences. Our model is superior to the existing methods and achieves the goal of accurate identification of datasets with small sample size. We try different word segmentation methods for peptide chains and prove the influence of pre-training steps and balancing datasets on the recognition effect. We find that pre-training on a large number of diverse AMP data, followed by fine-tuning on new data, is beneficial for capturing both new data’s specific features and common features between AMP sequences. Finally, we construct a new AMP dataset, on which we train a general AMP recognition model.

As one of the important parameters for lower hybrid wave (LHW) systems with 24 4.6 GHz/250 kW continuous-wave klystron amplifiers, the microwave power needs to be accurately acquired in real time for the experimental advanced superconducting tokamak (EAST) experiment. A new 4.6 GHz/250 kW directional coupler was developed for power measurements in an LHW system. The design principle and characteristic parameters of the coupler are discussed based on transmission line theory and the system requirements. The calculations and simulations indicate that the measurement error of the incident power is less than 5% when the isolation is greater than 25 dB. The directional coupler was also applied to the 4.6 GHz LHW system. The results show that the device can meet the requirements of LHW system operations. Comprehensive Research Facility for Fusion Technology(CRAFT)is being built. This work is beneficial to the design of power measurement system for LHW system.

A 324 MHz 200 kW waveguide-to-coaxial adaptor has been designed and fabricated for a microwave coupler in a radio frequency quadrupole system. Optimization of the adaptor is performed by the numerical study and experimental test. High-power measurements show that the reflection coefficient of the adaptor is less than −30 dB at the RFQ operating frequency, and there is no breakdown in the 228 kW pulse test. The measurement results are consistent with the simulation results, indicating that the adaptor has good high-power transmission performance. This work provides theoretical and experimental bases for a rectangular-to-coaxial adaptor design, especially in high-power steady-state operation.

Microwave plasma reactor is often of particular interest due to their wide range of industrial applications, especially in high-end manufacturing. However, there exist problems of unstable plasma and small discharge area in conventional microwave reactors at 2.45 GHz. An edge tapered 915 MHz/TM021 microwave reactor evolved from reactors at 2.45 GHz is presented to improve the strength, area, and uniformity of microwave field for plasma applications. An electromagnetic model of a microwave reactor with the new coupling antenna composed of a tapered platform and a coaxial inner conductor is simulated. The simulation results show that the electric field strength in the new reactor with a size optimized coupling structure is more concentrated compared to similar reactors. A 2D axisymmetric hydrogen plasma discharge model based on self-consistent fluid simulation of this new reactor is presented. The obtained results show that this kind of model can lead to a better understanding of the physical processes occurring in these kinds of microwave reactors.

A novel technique for coupling enhancement of coaxial antenna fed TM 021 resonant cavity is proposed in this paper. An inverted frustum section is inserted between the coaxial waveguide and the resonant cavity to improve coupling. The inverted frustum section acts as an impedance matching device that increases the coupling from waveguide to resonant cavity. The proposed structure has been simulated using Ansoft HFSS. The effect of various design parameters of the antenna on return loss characteristics is studied.

A C band Teflon water load is designed for the 4.6 GHz lower hybrid current drive (LHCD) system in the experimental advanced superconducting tokamak (EAST) to absorb the high power microwave reflected from the circulator, Teflon is used to substitute traditional ceramics to isolate the air and the water, which is cheaper and easier to processed. The simulation result carried out by CST microwave studio shows that the return loss reaches -64 dB at 4.6 GHz, and the power loss density was fitted by Origin software to calculate the thermal distribution of the Teflon and the water. Besides, the thermal analysis carried out by ANSYS indicates that this water load can work under 5 kW CW, with the maximum temperature of Teflon less than 71 °C, and the maximum thermal deformation and stress are no more than 0.14 mm and 3.2 MPa.

The launcher of the 4.6 GHz lower hybrid current drive (LHCD) system for the Experimental Advanced Superconducting Tokamak (EAST) consists of 24 antenna modules, each composed of an array of 3 (row) × 8 (column) waveguides. In order to verify the radio frequency (RF) design and the feasibility of the manufacturing process, a mock-up of the module has been fabricated and measured. The measured return losses of all three input waveguides are less than −25 dB at a frequency of 4.6 GHz. The transmission coefficients from the input waveguide to the output waveguides are −9.13 ± 0.2 dB and the insertion loss is 0.104 dB. These good results mean that the design method of the antenna module can be used for the new 4.6 GHz launcher on EAST. The detailed design of the multi-junction antenna module and its initial test result are described in this paper.