The self-lubricant wear-resistant NiCr/Cr3C2-10%WS2 coating and wear-resistant NiCr/Cr3C2 coating were obtained on Ti6Al4V by laser cladding. Microstructure of the coatings was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray energy dispersive spectrometer (EDS). The wear properties were evaluated using a ball-on-disc wear tester under dry sliding condition. The results show that the laser cladding NiCr/Cr3C2-10%WS2 composite coating has good friction-reducing and anti-wear capabilities at ambient.
Wavelet transform can characterize the local features of the signal in the time domain and frequency domain, enlarges and identifies the mutation signal of the structural response at different scales as a new signal analysis tools. In this paper, based on the structural deflection curve, propose a wavelet-based method to identify the beam structural damage. Use wavelet function to decompose the deflection curve of the structure after injury. Determine the existence of damage by the change and distribution of wavelet transform coefficients, determine the damage location, and simulate a cantilever bridge to verify this method.
The generation of runaway electrons (REs) is observed during the low-density helium ohmic plasma discharge in the Experimental Advanced Superconducting Tokamak (EAST). The growth rate of hard x-ray (HXR) is inversely proportional to the line-average density. Besides, the RE generation in helium plasma is higher than deuterium plasma at the same density, which is obtained by comparing the growth rate of HXR with the same discharge conditions. The potential reason is the higher electron temperature of helium plasma in the same current and electron density plateau. Furthermore, two Alfvén eigenmodes driven by REs have been observed. The frequency evolution of the mode is not fully satisfied with the Alfvén scaling and when extension of the Alfvén frequency is towards 0, the high frequency branch is ~50 kHz. The different spatial position of the two modes and the evolution of the helium concentration could be used to understand deviation between theoretical and experimental observation.
To study the influence of different quasi‐isentropic loading modes on the ignition and the detonation growth processes of PBXs, a one‐dimensional numerical model based on the DZK reaction rate model is presented, and then the parameters of DZK reaction rate model of PBXC03 can be experimental calibrated under the quasi‐isentropic loadings. Moreover, the ignition and detonation growth processes of PBXC03 under different quasi‐isentropic loading modes are simulated by using DYNA2D. It is found from the numerical results that both the increase of the peak pressure of shock front and the shock wave speed increase but the time to detonation decreases with the peak loading pressure, loading slope and curvature. It is also found that the explosive initiation process under the quasi‐isentropic loadings can be divided into two stages: one is the initial stage that manifests mainly as the catch‐up and convergence of the quasi‐isentropic waves and the formation of shock waves; the other is the stage of shock initiation, in which a shock wave with a certain intensity is formed and grows gradually into a stable detonation wave. In addition, a necessary condition is proposed to discriminate the feasibility of an quasi‐isentropic loading experimental calibration of the EOS parameters of a unreacted explosive, i. e., the sample's thickness must be smaller than the thickness of initial reaction.
Ohmic plasma currents of up to 17 kA with a discharge duration of 0.32 s have been obtained in the Kyushu University Experiment with Steady-State Spherical Tokamak (QUEST) with the help of electron cyclotron wave (ECW) and cancellation coils (CCs). The CCs, originally installed to create a field null in the plasma breakdown phase, are essential for producing plasma current in QUEST. Although the ohmic coil current is initially biased and then reduced completely to zero to induce the plasma current in 15-20 ms, we demonstrate that the flat top of the plasma current exceeding 20 ms is maintained by the vertical field after the ohmic current is switched off. This type of operation is quite favorable for extending pulsed operation to the steady state by electron Bernstein wave current drive (EBCD).
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