Haitao Wang's research while affiliated with Shanghai Jiao Tong University and other places

The conventional two-beam interferometry adopts only one expression about plasma density and thickness because only fringe shift is recognized from the recorded fringes. Therefore, the prior hypotheses that the plasma is thickness-uniform or circular symmetry have to be introduced to separate them, which limits the applied range and accuracy of the conventional method. This paper found that the laser beam will be deflected if the thickness changes, leading the recorded fringes to be defocused. As a result, a new expression relying on recognizing the defocus parameter of the recorded fringes is derived, and a pointwise separation algorithm to separate density and thickness is proposed based on the two expressions. Compared to the conventional algorithms, the new algorithm requires no hypotheses and thus has a wider applied range.

Design requirements of the structural features, the material properties, and the processing capabilities are hard to be satisfied in nanotechnologies simultaneously. In this paper, TiO 2 nanoparticles that are chemically reliable have been processed through the doctor blade method to realize a kind of field enhancement nanostructure, aiming to enhance the dielectric-barrier-discharge plasma actuation performance. It is found that the thrust enhancement rate could be approximately 72% at 13 kV and 8 kHz, compared to the controlled samples. In addition, a threshold phenomenon of the thrust enhancement effect was also found from the experiments, where the applied voltage and frequency lower than specific criteria could both lead to a decrease in the thrust generation and vice versa. It is suggested that the increase in the ionization frequency resulted from the field enhancement effect of the nanostructures is the leading mechanism for the extra thrust generation, which is inconsistent with the experimental examinations of the plasma characteristics and the plasma kinetic simulation. The results suggested that TiO 2 nanoparticles could be used to improve the actuation performance in harsh environments with sound substrate compatibility.

Conventional plasma absorbers are challenging to obtain high electron density and sizeable spatial scale for effective absorption while meeting the applied requirements of low profile and low power consumption. Although the frequency selective surface (FSS) has proved to realize a lower profile of plasma absorber with some empirical patterns adequately, the issue of the FSS design matching the dispersion distribution of complicated plasmas is still in suspense. A reverse prediction method referenced as the forecast and design Conditional Generative Adversarial Network (FD-CGAN) is proposed to generate a pixelated FSS between double-layer plasma periodic arrays. The reflection attenuation characteristics examined by experiments show that the addition of the FSS makes the coupling absorption effect surpass that of either pixelated FSS or plasma solely. Measurements in reconfigurable working modes and array arrangements demonstrate that the proposed configuration maximizes absorption effectiveness in the same profile, accompanied by the simulation. An interfacial void model is proposed to assist the design of the composite absorbing structure, together with an equivalent circuit for the hybrid absorber including periodic patterns with stochastic distribution characteristics, which analyze the absorption effect of the composite structure. The study provides a new approach for various microwave applications, including multilayer radar-absorbing structures, plasma-based stealth technology, and reconfigurable filters.

The transient plasma kinetic has been proved to be able to significantly improve the refrigerant efficiency of vacuum flash evaporation. Here we explore the flash evaporation cooling enhancement effect induced by a continuous glow discharge plasma, generally exists in vacuum, but the heat deposition is more severe than a transient plasma source. Several controlled groups with different discharge currents, which determine the thermal deposition rates, are subjected to an oscilloscope, CCD, and optical emission spectroscopy (OES) for diagnosis of plasma and Infrared Radiation (IR) thermography, vacuum gauge, and electronic balance for thermal and evaporative properties to reveal the influence of plasma characteristics on flash evaporation cooling. The characterization results of plasma show that the translational temperature increases with current while the rotational temperature and electron density are almost independent of current. Compared to plasma-free, the plasma generally leads to a significant increase in the maximum temperature drop (ΔTmax), but the effect increases with current from 0.95 to 3.07 mA and decreases at 3.87 mA. The behavior is attributed to the competition between the positive effect of evaporative cooling enhancement resulted from particle kinetic and the negative effect of joule heat itself. This has also led to that the system presents a best cooling enhancement efficiency defined by the increased ΔTmax per unit watt due to plasma, (ΔTmax(I)−ΔTmax(Plasma−free))/P, at the current of 2.01 mA for our cases. In conclusion, the continuous DC glow discharge plasma has been demonstrated to be useful to enhance flash evaporation cooling.

Researches in the plasma actuation are increasingly scrutinizing the methodology to enhance the thrust density for the application in the aerodynamic flow control. In this paper, a new method has been proposed and experimentally evaluated. This method is based on the deposition of nanoscaled structures on the electrode surface and the tuning of the applied voltages and frequency. It is found that the thrust enhancement rate resulted from the incorporation of the nanostructures could be approximately 78 \%, relative to the controlled group, under 14kV and 7kHz. However, a threshold effect has been founded across all of the tested samples, where lower applied voltage and frequency could lead to the decrease in the thrust generation. Capacitor charging effects are basically not sensitive to the introduction of the nanostructures in electrical characteristic. Other experimental features and electric filed simulation results also indicate the effectiveness of introducing nanoscaled structures into DBD plasma actuators, thus providing a new way to improve mechanical performance.

We reported a bandgap-tunable device with ternary plasma photonic crystals (PPCs), achieving tunable bandgap for controlling the propagation of free-space electromagnetic waves from 11.5 GHz to 14.5 GHz. The device is designed as a square crystal structure composing ternary PPCs arrays. Both simulation and experimental results indicate that the transmission of the electromagnetic waves can be controlled by changing the plasma frequency, dielectric constant, and structure spacing in the device, realizing the dynamic adjustment of photonic bandgap bandwidth and center frequency. In addition, the plasma frequency was measured, which is consistent with the simulation results. Our strategy can be applied to design a variety of devices, including reconfigurable antennas, plasma lenses, and military-developed stealth equipment.