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[en] Lithium tantalite (LiTaO) is an excellent single crystal, only a few studies focused on polycrystalline LiTaO ceramics, because it is difficult to sintering densification in fabrication process by common sintering. In this paper, LiTaO composite ceramics with added 3 wt% MnO were obtained by hot-pressing sintering at different temperatures from 1200 to 1350 °C. The sinterability, microstructure and dielectric properties of LiTaO ceramics fabricated at sintering temperatures were investigated. The relative density of the LiTaO ceramics was significantly enhanced as the sintering temperature increases first and then decreased. The LiTaO ceramics achieved the highest relative density (98.6%) and shown homogeneous microstructure when sintered at 1300 °C. The LiTaO and manganese oxide phases were observed in the MnO/LiTaO ceramics fabricated at different sintering temperatures. The dielectric properties of MnO/LiTaO ceramics were significantly influenced by the sintering temperatures. The study of dielectric properties revealed that the specimen had excellent dielectric properties when sintering temperature was 1300 °C and the dielectric constant was 78, as it tends to stay invariable at room temperature.
[en] Mg2-xAgxNi (x=0.05, 0.1, 0.5) prepared by hydriding combustion synthesis were investigated by means of pressure-composition isotherms, X-ray diffraction and scanning electron microscopy. The results showed that the maximum hydrogen absorption capacity of Mg1.95Ag0.05Ni is 3.49 mass% and of Mg1.9Ag0.1Ni 3.43 mass% at 553 K, just after synthesis without any activation; their desorption capacities are 3.31 mass% and 3.18 mass%, respectively. The XRD results explain that it is reasonable to add a little Ag in Mg2Ni and the kinetics of the Mg2-xAgxNi (x=0.05, 0.1) hydrogen storage alloy can be improved. The relationships between the equilibrium plateau pressure and temperature for Mg1.9Ag0.1Ni were log P(0.1 MPa)=-2827/T+5.677 (523 K ≤ T ≤ 573 K) for hydriding and log P(0.1 MPa)=-3581/T+6.818 (523 K ≤ T ≤ 573 K) for dehydriding. That of Mg1.95Ag0.05Ni were log P(0.1 MPa)=-2725/T+5.354 (523 K ≤ T ≤ 573 K) for hydriding and log P(0.1 MPa)=-3444/T+6.538 (523 ≤ T ≤ 573 K) for dehydriding
[en] Anti-synchronization between different hyperchaotic systems is presented using Lorenz and Liu systems. When the parameters of two systems are known, one can use active synchronization. When the parameters are unknown or uncertain, the adaptive synchronization is applied. The simulation results verify the effectiveness of the proposed two schemes for anti-synchronization between different hyperchaotic systems
[en] Using the mapping method based on q-deformed hyperbolic functions, the exact solutions of generalized Breor-Kaup equations are obtained. Based on the solutions, two coherent structures, periodic-branch kink and non-propagating kink, have been obtained. Moreover, one solitonal interaction form, two line solitons interaction on the kink background, has been found
[en] The entanglement dynamics of system, where atoms A and B interact with single mode cavity fields a and b respectively, is studied. The interaction between atom A and cavity a may be described by using the typical Jaynes–Cummings model, while that between the atom B and cavity b filled with a Kerr medium is of a two-photon process. For a certain initial atom entanglement state, there is an entanglement sudden death effect between the two atoms. The Kerr medium in the cavity b can effectively prevent the undesirable entanglement sudden death from occurring. Also, from the viewpoint of the population dynamics, we discuss why the Kerr medium can do so. (general)
[en] In this study, laponite was tested as a mud-making material for drilling fluids. Laponite is a synthetic smectite clay with a structure and composition closely resembling the natural clay mineral hectorite. Commercially available laponite was characterized by X-ray diffractometry, scanning electron microscopy and infrared spectrometry. Its dispersibility, salt resistance and high-temperature resistance were evaluated. The results showed that laponite possessed superior cation exchange capacity (140.4 mmol/100 g) with interlayer cations of Na+ and Li+. Laponite could easily be dispersed in water to yield increased viscosity with no influence from hydration time or temperature. On the other hand, laponite dispersions displayed an excellent heat resistance, with invariant apparent viscosity at high temperatures. For instance, the apparent viscosity of the 2 wt% laponite dispersion underwent changes between 22 and 24 mPa s after hot rolling at 180–240 °C for 16 h. Compared to existing mud-making materials, laponite exhibited better mud-making properties. Furthermore, laponite revealed good compatibility with other additives, and the water-based drilling fluids prepared with laponite as mud-making material showed an excellent stability at elevated temperatures and superior performance–cost ratios. Overall, these findings indicated that laponite had an excellent dispersibility at high temperatures and hence would have promising applications as high-temperature mud-making material for preparing water-based drilling fluids designed for ultra-high-temperature environments.
[en] The characteristic of bubble growth is visually observed in a narrow rectangular channel using high speed camera. The experiment was conducted over the following range of conditions: pressure, 0.55 MPa; mean liquid velocity, 300∼500 kg/(m"2 · s); heat flux, 86.4∼225.7 kW/m"2; and inlet subcooling, 25.5∼45.5 K. Experimental results show that the bubble diameter is just about 0.15 mm under higher system pressure and the period during which bubbles attaching to the nucleate site is very short. The bubbles keep growing when slide along the heating wall rather than lifting off the surface, and the bubbles rarely collapse in the observation window. When the mass flux is high, the bubble diameter increases with increasing the heat flux, but when the mass flux is low, the variation trend of bubble diameters expresses no obvious law. The bubble diameter decreases with increasing the inlet subcooling. At high inlet subcooling, the bubble diameter decreases with increasing the mass flux, however at lower mass flux, the mass flux has less effect on bubble diameters. (authors)
[en] The bubble coalescence in narrow rectangular channel during subcooled boiling was studied by experiment. The channel size was 2 mm × 40 mm × 700 mm and the experiment parameters were as following: The inlet absolute pressure P_i_n = 0. 55 MPa, the inlet subcooling Δt_i_n = 31℃, the mass flux G = 516 kg/(m"2 · s) and the average velocity ν = 0.52 m/s. The high speed camera was used to photograph the bubbles and the speed was set as 5000 frame per second. The bubble coalescence process was divided into four stages: The approaching stage, the coalescence stage, the adjustment stage and the steady stage. After coalescence, the bubble velocity would increase and then decrease, and finally approach steady. The ellipsoid and sphere bubble shapes would alternate to appear. Along with the shape changing, the angle and the axis length would change also. Finally, a new small bubble may be induced during the coalescence process. (authors)