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The rich nontrivial topological phases rooted in the interplay between magnetism and topology in the layered antiferromagnet EuCd2As2 have captured vast attention, especially the ideal Weyl semimetal state realized in the spin-polarized ferromagnetic (FM) structure driven by a moderate external magnetic field. In this work, combining high-pressure magnetotransport measurements, structure chracterizations and first principles calculations, we find that application of pressure can also realize the ideal Weyl state in EuCd2As2 through driving the in-plane antiferromagnetic state across an intermediate in-plane FM state then into the out-of-plane FM state. Our high-pressure angle dispersive X-ray diffraction and X-ray absorption near-edge spectroscopy measurements excluded structure transition and/or change of Eu2+ valence state as the sources for the magnetic phase transitions. Alternatively, the apparently reduced axial ratio (c/a) and compressed Eu-layer space distance should play important roles. Our result provides an alternative way to realize the ideal Weyl semimetal state in EuCd2As2 and would be instructive for the exploration of exotic topological properties in such layered magnetic topological phase with strongly competing magnetic exchanges by using high pressure., Comment: main text 16 pages,4 figures and SI 8 pages, 4 figures

With the large-scale integration of wind power into the grid, a model that can accurately describe the randomness of wind farm output and the correlation between them is of great significance to be constructed. A joint distribution function of multiple wind plants output model based on Copula theory is constructed. By introducing correlation and fitting coefficient, the attribute recognition theory is put forward to select the optimal model based on entropy weight method. Finally, the validity of Copula modeling is verified by using the synchronized historical data of California coastal wind farms as a sample. The results show that t-copula can not only describe the correlation between the original variables well, but also fit the empirical distribution function of the original samples accurately.

The high temperature oxidation behavior of Fe–C (0.22%)–Mn (5.3%)–Al (2.5–3.2%)–Si (2.2%) low density steel was studied in the atmosphere of (2%O2 + Ar) by high temperature oxidation simulation tests. The samples were kept at 900 °C–1300 °C for 30 minutes and the morphology and the content distribution of oxide layer in the scale were characterized by scanning electron microscope combined with energy dispersive spectrometer. The results show that: when the holding temperature is below 1150 °C, the oxidized weight gain increases parabolically with time; when the temperature is maintained above 1200 °C, the oxidized weight gain increases linearly. Oxidation activation energy decreases with experimental temperature from 225.31 to 43.4 kJ/mol and due to formation of liquid oxidation products the value of Ea decreases sharply from 1100 °C.For all range of temperature the outer layer of the scale is FeOn–MnO oxide while the scale is mainly SiO2–Al2O3–FeOn–MnO near the matrix. Few variations could be observed for the morphology of scales when the heating temperature ranged from 900 °C to 1100 °C. When the heating temperature is over 1150 °C the liquid Fe2SiO4 and FeO–SiO2–MnO phases in the scale were newly formed, leading to the penetration of liquid oxide scale into the steel, which makes descaling difficult. Therefore, to facilitate the descaling operation before hot rolling, temperature should be controlled below 1150 °C in the reheating furnace.

The output voltage of small wind driven generator presented non-cyclical fluctuation affected by wind speed, which then leads to unstable accumulator charging voltage. In order to improve charging efficiency and prolong accumulator's service life, this paper designed a steady voltage circuit based on UC3842. It is mainly composed by rectifier filter circuit, Buck chopper circuit and post-processing circuit. With wind power variation, the duty ratio of PWM wave outputted by UC3842 is changing accordingly. Then, the circuit will output steady voltage to charge accumulators. This design is characterized by simple circuit, relatively low cost and convenient maintenance etc.

The aluminum-substituted α-Ni(OH) 2 was prepared by direct titration method in a buffer solution. The structure was analyzed by XRD, IR and TG. Its electrochemical properties as a positive electrode in Ni-metal hydride cell were examined by the charge–discharge experiments. The results indicate that the electrode performances of the aluminum-substituted α-Ni(OH) 2 are superior to general β-Ni(OH) 2 , especially, the specific capacity of discharge, the specific energy of discharge and the cycle life have been enhanced obviously.

Nanocrystalline composite oxide SrRuO 3 was synthesized by the reverse drop coprecipitation method. Pure SrRuO 3 and SrRuO 3 adsorbed on active carbon powder were used as negative electrode material in the fuel cell, the cell performances were examined by cyclic voltammetry. The experiments indicated that the new electrodes are better electrocatalysts for methanol oxidation. Moreover, the structure and morphology of nanocrystalline SrRuO 3 were characterized by XRD and TEM.

The precursors for synthesis of nanocrystalline composite oxides La1−xSrxFe1−yCoyO3 (x = 0.2, 0.4; y = 0.5, 0.6) were prepared using the polyethylene glycol and citrate methods. After the solid-phase reaction at 550°C for 2 h, the mean diameters of the nanocrystalline grains were about 15 nm. The results indicate that the effects of the solid-phase reaction depend on the distribution of various components in the precursor and the conditions of preparing them. The polyethylene glycol method is superior in many respects to the citrate method.