•AlNiCoCuFeNi high-entropy alloy (HEA) was fabricated on Mg substrates using laser cladding.•No serious dilution of the HEA composition occurred in the top-layer of the coating.•The phenomenon of Cu ...rejection was analysed based on Gibbs free energy.•Solidification behaviour of the HEA was studied using the Kurz–Giovanola–Trivedi and the Gaümann models.
The AlCoCrCuFeNi high-entropy alloy (HEA) was fabricated on pure magnesium substrates by means of laser cladding using a direct blown powder method. The coating can be categorised into two layers, a top AlCoCrCuFeNi HEA layer and a lower composite layer that consists of some partially melted HEA powders in an Mg based matrix. A metallurgically bonded interface was obtained between the Mg substrate and the HEA coating, with epitaxial crystals formed at the melting boundary of the substrate. In the solidification of the HEA alloy, some Cu was rejected into the Mg melt, however, no serious dilution of the HEA composition occurred in the top layer of the coating. The phenomenon of Cu rejection was analysed based on Gibbs free energy. Moreover, the solidification behaviour of the HEA was studied using the Kurz–Giovanola–Trivedi and the Gaümann models with modifications for multi-component alloys.
•The analytical derivation of the moment enslavement scheme with good convergence.•Successful application to the 1D shear Alfvén wave in a broad range of β/me.•The development of the mixed ...particle-in-cell-particle-in-Fourier scheme in torus.•Simulations of toroid Alfvén eigenmodes using a widely studied ITPA case.
In this work, an implicit scheme for particle-in-cell/Fourier electromagnetic simulations is developed and applied to studies of Alfvén waves in one dimension and three dimensional tokamak plasmas. An analytical treatment is introduced to achieve efficient convergence of the iterative solution of the implicit field-particle system. First, its application to the one-dimensional uniform plasma demonstrates its applicability in a broad range of β/me values. Second, toroidicity induced Alfvén eigenmodes (TAE) are simulated in a three dimensional axisymmetric tokamak plasma, using the widely studied case defined by the International Tokamak Physics Activity (ITPA) Energetic Particle (EP) Topical Group. The real frequency and the growth (or damping) rate of the TAE with (or without) EPs agree with previous results reasonably well. The full f electromagnetic particle scheme established in this work provides a possible natural choice for EP transport studies where large profile variation and arbitrary particle distribution functions need to be treated in kinetic simulations.
Abstract The RNG k - ε turbulence model and mass transport cavitation model Zwart-Gerber-Belamri are used to simulate unsteady cavitating flows in a rotational hydrodynamic cavitation reactor (RHCR). ...The RHCR is mainly composed of rotor and stator. Unsteady cavitation flow field analyses in RHCR are focused mainly near the rotor surface. The numerical simulation results are in good agreement with the experimental data. The frequency of pressure fluctuations and streamline distribution are discussed by setting 10 monitoring points near the rotor surface. The numerical simulation results shows that the main frequency of pressure fluctuation inside RHCR is 24 f r and 72 f r ; the maximum amplitude of pressure fluctuations appears near the inlet, and its value about 3 times than the minimum. Moreover, the streamline distribution analyses demonstrate that the vortex appears near the rotor surface, and is generating, growth and disappearing with time. The shape, vortex center and intensity of the vortex near the inlet change drastically with time. This research provided a reference for the optimization design of RHCR.
The effects of corrosion product deposit on the subsequent anodic and cathodic reactions of X-70 steel in a near-neutral pH solution were investigated by localized electrochemical impedance ...spectroscopy (LEIS), scanning vibrating micro-electrode (SVME) and macroscopic EIS measurements as well as surface analysis technique. It is found that the deposit layer formed on the steel surface is porous, non-compact in nature. The presence of a corrosion product layer would enhance adsorption, but significantly inhibit absorption and permeation of hydrogen atoms into steel. It is due to the porous structure of the deposit that generates a spatial separation of cathodic and anodic reaction sites, resulting in an increased effective surface area for hydrogen adsorption and, simultaneously, a “blocking” effect on hydrogen absorption and permeation. The deposit enhances greatly anodic dissolution of the steel, which is attributed to the adsorption of the intermediate species and the resultant “self-catalytic” mechanism for corrosion of the steel in near-neutral pH solution. In the presence of corrosion product deposit on the pipeline steel surface, pipeline corrosion, especially pitting corrosion, is expected to be enhanced. Stress corrosion cracks could initiate from the corrosion pits that form under deposit. However, deposit does not contribute to hydrogen permeation, although the hydrogen evolution is enhanced.
Interest in parameterized time-frequency analysis for non-stationary signal processing is increasing steadily. An important advantage of such analysis is to provide highly concentrated time-frequency ...representation with signal-dependent resolution. In this paper, a general scheme, named as general parameterized time-frequency transform (GPTF transform), is proposed for carrying out parameterized time-frequency analysis. The GPTF transform is defined by applying generalized kernel based rotation operator and shift operator. It provides the availability of a single generalized time-frequency transform for applications on signals of different natures. Furthermore, by replacing kernel function, it facilitates the implementation of various parameterized time - frequency transforms from the same standpoint. The desirable properties and the dual definition in the frequency domain of GPTF transform are also described in this paper. One of the advantages of the GPTF transform is that the generalized kernel can be customized to characterize the time - frequency signature of non-stationary signal. As different kernel formulation has bias toward the signal to be analyzed, a proper kernel is vital to the GPTF. Thus, several potential kernels are provided and discussed in this paper to develop the desired parameterized time - frequency transforms. In real applications, it is desired to identify proper kernel with respect to the considered signal. This motivates us to propose an effective method to identify the kernel for the GPTF.
To investigate whether procalcitonin (PCT) can improve the performance of quick sequential organ failure assessment (SOFA) score in predicting sepsis mortality, we conducted a retrospective ...multicenter cohort study with independent validation in a prospectively collected cohort in 3 tertiary medical centers. Patients with presumed sepsis were included. Serum PCT levels were measured at admission. Quick SOFA score and systemic inflammatory response syndrome (SIRS) criteria were calculated for each patient. PCT levels were assigned into 0, 1, and 2 points for a serum level of <0.25, 0.25 to 2, and >2 ng/mL, and added to the quick sepsis-related organ failure assessment (qSOFA) score. The incremental value of PCT to qSOFA was then evaluated by logistic regression, receiver-operating characteristic (ROC) curve, and reclassification analysis.In all, 1318 patients with presumed severe infection were enrolled with a 30-day mortality of 13.5%. Serum level of PCT showed a high correlation with qSOFA score and 30-day inhospital mortality. The area under the ROC curve was 0.56 for SIRS criteria, 0.67 for qSOFA score, and 0.73 for qSOFA_PCT in predicting 30-day mortality. The risk prediction improvement was reflected by a net reclassification improvement of 35% (17%-52%). Incorporation of PCT into the qSOFA model could raise the sensitivity to 86.5% (95% confidence interval 80.6%-91.2%). In the validation cohort, qSOFA_PCT greatly improved the sensitivity to 90.9%.A simple modification of qSOFA score by adding the ordinal scale of PCT value to qSOFA could greatly improve the suboptimal sensitivity problem of qSOFA and may serve as a quick screening tool for early identification of sepsis.
Passivity of aluminum (Al) alloy 3003 in air and in aqueous solutions without and with chloride ions was characterized by electrochemical measurements, including cyclic polarization, electrochemical ...impedance spectroscopy (EIS), localized EIS and potential of zero charge, Mott–Schottky analysis and secondary ion mass spectroscopy (SIMS) technique. Stability, pitting susceptibility and repassivation ability of Al alloy 3003 under various film-forming conditions were determined. Results demonstrated that passive films formed on 3003 Al alloy in air and in Na
2SO
4 solution without and with NaCl addition show an n-type semiconductor in nature. The passive film formed in chloride-free solution is most stable, and that formed in chloride-containing solution is most unstable, with the film formed in air in between. Pitting of Al alloy 3003 passivated both in air and in aqueous solutions is inevitable in the presence of chloride ions. There is the strongest capability for the air-passivated Al alloy 3003 to repassivate, and the weakest repassivating capability for Al alloy 3003 passivated in chloride-containing solution. The resistance of the passivated Al alloy 3003 to pitting corrosion is dependent on the competitive effects of pitting (breakdown of passive film) and repassivation (repair of passive film). According to the differences between corrosion potential and potential of zero charge, passive film formed in air has the strongest capability to adsorb chloride ions, while the film formed in chloride-containing solution the least. Chloride ions causing pitting of passivated Al alloy 3003 in air and in chloride-free solution come from the test solution, while those resulting in pitting of passivated Al alloy 3003 in chloride-containing solution mainly exist in the film during film-forming stage.
A novel photocatalysis and gas sensing material was synthesized by decorating Au nanoparticles on tungsten trioxide nanorods. Tungsten trioxide nanorods were prepared through the ion-exchange method ...combined with hydrothermal treatment and further modified with Au nanoparticles (Au NPs). After Au NPs decorated on the surface of WO3 nanorods (WO3 NRs), the reducing gas (hydrogen, methanol, ethanol, etc.) sensing properties and the photocatalytic performance of rhodamine B (RhB) were all greatly improved. Au NP modified WO3 nanorods (Au NP@WO3 NRs) exhibit not only larger response (H2 50 ppm, recovery time lower than 10 s) and better selectivity (Ra/Rg = 6.6) for H2 gas detection than pure WO3 NRs but also high photocatalytic properties for the absolute degradation of RhB under simulated sunlight irradiation for 120 min.
The conventional time-frequency analysis (TFA) methods, including continuous wavelet transform, short-time Fourier transform, and Wigner-Ville distribution, have played important roles in analyzing ...nonstationary signals. However, they often show less capability in dealing with nonstationary signals with time-varying frequency due to the bad energy concentration in the time-frequency plane. On the other hand, by introducing an extra transform kernel that matches the instantaneous frequency of the signal, parameterized TFA methods show powerful ability in characterizing time-frequency patterns of nonstationary signals with time-varying frequency. In this paper, a novel time-frequency transform, called spline-kernelled chirplet transform (SCT), is proposed. By introducing a frequency-rotate operator and a frequency-shift operator constructed with spline kernel function, the SCT is particularly powerful for the strongly nonlinear frequency-modulated signals. In addition, an effective algorithm is developed to estimate the parameters of transform kernel in the SCT. The capabilities of the SCT and parameter estimation algorithm are validated by their applications for numerical signals and a set of vibration signal collected from a rotor test rig.
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