Journal of Inorganic Materials,Vol 32,No. 12
MgO-ZnO thermal control coatings were prepared on AZ31 Mg alloy using micro-arc oxidation (MAO) in the electrolyte containing Zn(H 2PO 4) 2. The influences of current density on the microstructure, composition, adhesive strength, and thermal control performances of MAO coatings were investigated, and the variation of solar absorptance ( αs) was examined at different ultraviolet irradiation time. The results show that the MAO coating is composed of MgO, ZnO and a few amorphous phases. With an increase of current density, the number of pores gradually decreases while the roughness increases. And the thickness, the adhesion and emittance ( ε) firstly increase and then decrease, the changing tendency of αs shows the opposite. When the current density is set at 9 A/dm 2, the MAO coating exhibits a stronger adhesive strength of 12.6 MPa, a higher ε of 0.872 and a lower αs of 0.363. Moreover, the ultraviolet irradiation test reveals that the αs increases followed by leveling off with increasing irradiation time. This process provides a technical support for fabricating the thermal control coating with excellent adhesion, low αs/ ε ratio, and good anti-ultraviolet irradiation capability.
Regrowth of CdTe Quantum Dots Induced by Circular Polarized Light and Its Effect on the Photoluminescence
Journal of Inorganic Materials,Vol 32,No. 12
The water soluble CdTe quantum dots were synthesized in aqueous solution using 3-mercaptopropionic acid as stabilizer reagent. The effects of non-polarized and circular polarized light modification on the structural and optical properties of quantum dots were investigated by photoluminescence spectroscope, ultraviolet visible absorption spectroscope, transmission electron microscope, and X-ray diffraction. It is revealed that the non-polarized light tends to oxidize the quantum dots, which brings about photo degradation of quantum dots and blue shift of photoluminescence. By contrast, the circular polarized light oxidizes the stabilizer reagent at the surface of CdTe quantum dots, which leads to regrowth of quantum dots and red shift of photoluminescence. Moreover, the photochemical reaction mechanism together with the bonding effect between stabilizer reagent and CdTe quantum dot was studied. The photoluminescence of CdTe quantum dot is associated with its surface states.
Taiwan Studies,No. 02
In the 1970s, Zbigniew Kazimierz Brzeziński made great efforts on Taiwan question for the normalization of Sino-U.S. relationship, including putting forward the timetable for the first time, implementing three principles of “severing its diplomatic relations with Taiwan, abrogating the mutual defense treaty between the U.S. and Taiwan and withdrawing all U.S. forces from Taiwan” and so on. Still, he felt great pressure from his colleague the Secretary of State Vance, the Pro-Taiwan congressmen and the “Taiwan Lobby” behind. From this case study, it could be concluded that the U.S. made its Taiwan policy not just out of its national interest but also out of the competition within the executive branch and the completion between the executive branch and the congress.
A Method to Identify the Second Reverse Traveling Wave Induced by Single-phase-to-ground Fault in Transmission Line
Proceedings of the CSEE,Vol 36,No. 08
Identification of the second traveling wave reflected from the fault point or the remote-end bus is the core of traveling wave based single-end fault location and distance protection with fault location. A method is proposed to identify the second reverse traveling wave based on the cross transmission phenomenon of modal traveling waves in the single-phase-to-ground fault of transmission line, which is independent of the configuration of buses at both ends. The method firstly utilizes the initial traveling wave and the second reverse traveling wave to locate the fault initially and determine the fault area. Then, the relevant characteristic traveling wave pair of the second reverse traveling wave is recognized according to the fault area. Finally, the polarity relation of second reverse traveling wave and its relevant characteristic traveling wave pair are used to identify the source of second reverse traveling wave. If the polarity of the second reverse traveling wave and the polarity of the relevant characteristic traveling wave pair is the same, the second reverse traveling wave is reflected from the fault point; otherwise, from the bus at the remote end. A large number of EMTP simulation cases are carried out, verifying the correctness and validity of the method.
Transactions of the Chinese Society of Agricultural Engineering,Vol 32,No. 13
In order to investigate the general rule of soil conditions and working parameters on power consumption of disc type ditcher, LS-DYNA software of which the transient dynamic finite element analysis using explicit time integration was employed to simulate the process of soil cutting in this paper, and MAT147 model was used as constitutive model to build soil model, then with given specific parameters, the characteristics of yellow loam in north China was simulated. Due to the complexity of construction for ditching part, the model was initially set up in Soildworks, then imported into LS-DYNA. In order to shorten the operation time, the secondary characteristics such as chamfer, fillet and connection, was omitted. Aiming to study the physical process of soil cutting, we stimulated the finite element model of soil cutting by using Smoothed Particle Hydrodynamics. The deformation of soil was generated when subjected to extrusion of blade. As the amount of deformation was big enough, the soil would be broken. According to the results of simulation, the relationship between power consumption and time of ditching part in soil cutting process was obtained. Any two blades mounted in disk were simultaneously used to assure cutting smoothness and steady. As such, the second blade has been inserted into soil before the first one departed from soil. The total power assumption included kinetic energy from rotational motion of ditching part and internal energy from interaction with soils. At the beginning of soil cutting, power consumption increased quickly, which was caused by a great deal of power consumption needed during the process of soil deformation and broken. According to the results of simulation, it was found that the cutting power consumed was from 0 to 24.2 kW during the time of 0 to 13 ms, and the consumption reached maximum 36.26 kW, when cutting motion arrived at the time of 26 ms. After that, the power consumption tended to be stable, indicating that the binding force tended to be less after the soil particle was destroyed. The cutting force was then maintained at steady state, so the power consumption subsequently changed slowly and maintained about 32.5 kW. Orthogonal simulation experiment was carried out with soil firmness, rotation speed of cutting wheel and ditching depth as experiment factors and with power consumption of rotary ditching part as assessment index. It can be concluded that soil firmness, rotation speed of cutting disk and ditching depth had a larger effect on power consumption. By range analysis method and variance analysis method, the importance index can be determined for power consumption, and the results were soil firmness, ditching depth, and rotation speed of cutting disk. The mathematical model of impact factor and performance index was then established using MATLAB software, the minimum power consumption was 32.5 kW when the parameters of soil firmness, rotary velocity and ditching depth were 120 N/cm 2, 225 r/min and 405 mm, respectively. Finally, the field test was conducted to verify the accuracy of simulation results and optional parameters. It has shown that the relative error between theoretical and testing values was 5.68%, showing that the simulated value was basically coincided with testing value, which proved that the modeling and simulating methods adopted met the content requirement. The results provide references for the product designers to select economic power consumption parameters and working conditions with different working parameters.