[en] This paper deals with the TiN coating of a new low alloy high speed steel W3Mo2Cr4VSi. According to transmission electron microscopy and X-ray diffraction investigations, the TiN coating can be divided into two layers: the main-body layer and the transition layer. The main-body layer consists of columnar TiN which is vertical to the substrate surface, with fine-grained TiN and small amounts of ε-Ti₂N between some columns. The transition layer is composed of equiaxed grains of TiN, ε-Ti₂N and α-Fe. The orientation relationship between the columnar TiN and the ε-Ti₂N grains in the main-body layer was found to be (101)_Ti2N parallel (200)_TiN and [111]_Ti2N parallel [011]_TiN. It was shown that the amount of α-Fe in the transition layer decreased with increasing silicon content to this steel. A compressive residual stress between 180 and 200 N mm^-2 exists in the coating. (orig.)

[en] It is demonstrated that Smale-horseshoe chaos exists in the time evolution of the one-dimensional Bose—Einstein condensate driven by time-periodic harmonic or inverted-harmonic potential. A formally exact solution of the time-dependent Gross—Pitaevskii equation is constructed, which describes the matter shock waves with chaotic or periodic amplitudes and phases

[en] Driven by the goal of studying the temperature changes in the nozzle and equipment cabin of solid rocket motor during the whole process of ignition starting, working, cooling and decompression, this paper uses the fluid dynamics software which uses the RNG k-ε turbulence model to simulate the mixing of the fuel and oxidant and the Sutherland law to describe the viscosity of gas and air, and the controlling equation is the two-dimensional axisymmetric viscous compressible URANS equation. In this paper, the temperature field of the nozzle and equipment cabin in the working process of solid rocket motor during 0 ∼ 60s is numerically simulated, and the ground experiment is carried out. The results show that (1) the numerical simulation results are in good agreement with the ground test results, and the absolute value of the maximum error appears at the time of 60s, which is 5.9k. indicating that the numerical calculation method and heat source equivalent method established in this paper are suitable for the temperature field simulation of composite structure nozzle and equipment cabin, (2) the unsmooth surface of the nozzle formed by high temperature ablation makes the flow situation in the divergent section of the nozzle complex and affects the heat transfer coefficient of the wall contacting with the equipment cabin, (3) due to the insulation design of the equipment cabin, only a small part of the heat is transferred to the equipment cabin. During the whole working process of solid rocket motor, the temperature field of equipment cabin increases sharply at both ends and gently in the middle. (paper)

[en] We propose and realize a new optical state selection method on a cesium atomic fountain clock by applying a two-laser 3–3′ optical pumping configuration to spin polarize atoms. The atoms are prepared in |F = 3, m_F = 0〉 clock state with optical pumping directly after being launched up, followed by a pushing beam to push away the atoms remaining in the |F = 4〉 state. With a state selection efficiency exceeding 92%, this optical method can substitute the traditional microwave state selection, and helps to develop a more compact physical package. A Ramsey fringe has been achieved with this optical state selection method, and a contrast of 90% is obtained with a full width half maximum of 0.92 Hz. The short-term frequency stability of 6.8 × 10⁻¹⁴ (τ/s)^−1/2 is acquired. In addition, the number of detected atoms is increased by a factor of 1.7 with the optical state selection. (paper)

[en] TiO₂ films, showing superhydrophilic behavior, are prepared by electron beam evaporation. Atomic force microscopy and the contact angle measurement were performed to characterize the morphology and wetting behavior of the TiO₂ films. Most studies attribute the wetting behavior of TiO₂ surfaces to their physical characteristics rather than surface chemistry. These physical characteristics include surface morphology, roughness, and agglomerate size. We arrange these parameters in order of effectiveness. Surface morphologies are demonstrated to be the most important. TiO₂ films with particular morphologies show superhydrophilic behavior without external stimuli, and these thin films also show stable anti-contamination properties during cyclical wetting and drying. (cross-disciplinary physics and related areas of science and technology)

[en] Highlights: • α-Fe₂O₃ is highly efficient to transform PAHs without light irradiation. • Oxygen vacancy concentration affects the PAHs degradation rate. • Oxygen vacancy contributes to the exposure of Fe(III) and provides active sites. • Catalytic efficiency is dependent on the synergistic effects of Fe(III) and O vacancies. The abiotic transformation of polycyclic aromatic hydrocarbons (PAHs) is significantly impacted by soil components, especially inorganic redox species like iron oxides. In this study, the catalytic activities of three types of iron oxides in PAHs degradation without light irradiation were evaluated using a combination of experimental techniques. The results showed that α-Fe₂O₃ possessed the highest transformation rate for anthracene (ANT), with a reaction rate constant (K_obs) up to 0.28 d⁻¹, followed by Fe₃O₄ (K_obs = 0.06 d⁻¹) and α-FeOOH (K_obs = 0.06 d⁻¹). X-ray photoelectron spectroscopy (XPS) characterization suggested that α-Fe₂O₃ had the highest oxygen vacancy concentration, which was conducive to the adsorption of O₂ by α-Fe₂O₃, providing sufficient adsorbed oxygen species. Oxygen vacancy contributed to the exposure of Fe(III), and accordingly, more active sites were created that were responsible for ANT degradation. According to these results, two possible pathways for the degradation of PAHs on iron oxides can be concluded: (1) direct oxidation by Fe(III) and (2) oxidation by the O₂^{• −} generated onto oxygen vacancies. This study provides significant insights into the environmental fate of PAHs on iron oxides, and raises the possibility that iron oxides may be used as catalytic materials in the remediation PAHs-contaminated soil.