Systematic manipulation of nanocrystal shapes is prerequisite for revealing their shape-dependent physical and chemical properties. Here we successfully prepared a complex shape of Pt micro/nanocrystals: convex hexoctahedron (HOH) enclosed with 48 {15 5 3} high-index facets by electrochemical square-wave-potential (SWP) method. This shape is the last crystal single form that had not been achieved previously for face-centered-cubic (fcc) metals. We further realized the shape evolution of Pt nanocrystals with high-index facets from tetrahexahedron (THH) to the HOH, and finally to trapezohedron (TPH) by increasing either the upper (EU) or lower potential (EL). The shape evolution, accompanied by the decrease of low-coordinated kink atoms, can be correlated with the competitive interactions between preferentially oxidative dissolution of kink atoms at high EU and the redeposition of Pt atoms at the EL.
Electric vehicles are currently a key development target in the transportation field, and wireless charging technology applied to electric vehicles is at the forefront of development. Due to the gap between the transmitting and receiving coils of the wireless energy transmission system, it is inevitable that metal foreign objects will enter the charging magnetic field area, which not only reduces charging efficiency but also poses serious safety hazards. A foreign object detection scheme based on system self-excited oscillation circuit feature extraction is proposed in this article. A single rectangular detection coil is designed, with six random foreign object points set. The frequency and amplitude of the oscillation circuit current waveform are detected to determine whether there are metal foreign objects in this system, and the feasibility of the scheme is verified through simulation.
In the Indosinian and early Yanshanian orogenies, the buried hill structure rose because of compression and thrusting. After the Carboniferous and Permian had been peeled, the Ordovician was weathered and leached for a long time. The compressed and thrust high angle crevice, the weathered and leached interparticle aperture and solution cave are the main space for the reservoir. With the abasing of the stratum static load, the bulk of the core sample come into expansion. Because the compressibility factor of the rock skeleton is small, the interstitical pore space is larger. Therefore, the measure pressure of original porosity and interstitical ratio on the surface must be equal to downhole pressure. The static pressure of the reservoir bed is 45 MPa. Finally, the measured comprehensive voidage is 4.7%. They are divided into 4 level reservoir beds. Among them the Ⅰ and Ⅱ level beds are the strongest reservoirs for oil gas storage and production in the region. They can obtain smooth high capacity oil and gas.
In this article, we present an analysis of electric fields and derivative waveforms radiated from lightning return stroke in the presence of an attachment point above the ground. Return stroke initiated from the ground (RSG), return stroke initiated from an attachment point above the ground (RSAP), and return stroke initiated from the attachment point considering current reflection from the ground (RSAPR) were considered and compared. Both first and subsequent return strokes were included in the simulation. It is shown that the presence of the attachment point results in a noticeable initial sharp peak on the electric fields and the derivative waveform was characterized by larger positive peak and negative overshoot. Both the electric field and derivative waveforms in RSAPR were much similar and closer to the results from RSG due to the current reflection from the ground. The influences on the electric fields and derivative waveforms were also discussed, including velocity of upward and downward wave, the attachment point height, reflection coefficient from the ground, and wave velocity of the reflected wave. The simulated results were also compared to the measured fields.
This essay presents the DSP + FPGA structure based high-performance image processing system.It aims at solving the overtime-processing problem brought by the increasing complexity of images through the cache-structured image-processing driver.This system allows frame-dropping whenever the processing of images runs overtime and achieves one frame.The system simulation result shows in this way the diver achieves higher efficiency than traditional ping-pong mode when dealing with the overtime-processing of images.
Position detection is the most important part in electric vehicle (EV) wireless charging system. It is used for coupling mechanism alignment. Usually, most position detection used the visual method with camera. But it is expensive and complicated. In this paper, based on EC-WPT system of double T-LCL topology, the formula of relation between output voltage and position is derived, the simulation analysis is carried out when the coupling mechanism plate is in different positions, and the change of output voltage is detected, so as to obtain the curve of output voltage and the position of the plate, and obtained the relationship between plate position and output voltage.
In the modeling of wireless power transfer systems, traditional modeling approaches often result in high-order models. In order to obtain a simplified model that can explain the input-output relationship of the system, this paper focuses on the LCC-LCC resonant compensating wireless power transfer system and proposes a method for establishing a dynamic model based on phase control. The model is then reduced to a first-order model using Taylor series expansion. Through comparison, it is found that the accuracy of this first-order model is not significantly compromised.
To solve the problem of low transmission efficiency in the magnetic coupled resonant wireless power transfer (MCR-WPT) system, a parameter design method based on chaotic sparrow search algorithm is proposed to optimize the transmission efficiency of the system. The circuit model of the two-coil MCR-WPT system is established, and the relationships among output power, transmission efficiency, frequency, coupling coefficient and load resistance are derived. The influence of frequency, coupling coefficient and load resistance on the output power and transmission efficiency of the system is studied and analyzed by the control variable method. The sparrow search algorithm is improved by using chaotic reverse learning strategy, and the three parameters were optimized by the improved algorithm, and the system parameter values corresponding to the optimal solution are obtained. Simulation results show that the transmission efficiency of the optimized MCR-WPT system can reach up to 91%.
The development of the effect of air-sea interaction on tropical cyclones over the past several decades is reviewed.It is obvious that SST and sea spray can affect the intensity and moving path of a tropical cyclone,but when it comes to the degree of the impact,there remains disagreement.Meso-scale coupled air-sea modeling system is a good tool to study the impact of air-sea interaction on tropical cyclones.Some meso-scale coupled air-sea models are introduced in order to set up a coupled air-sea modeling system which is fit for China sea area to simulate and forecast tropical cyclones.
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