Optical second harmonics (SH) has important applications in many fields, such as micro-imaging techniques and extending the wavelength band of laser light sources. Lithium niobate (LiNbO3) can achieve a high SH conver...
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Optical second harmonics (SH) has important applications in many fields, such as micro-imaging techniques and extending the wavelength band of laser light sources. Lithium niobate (LiNbO3) can achieve a high SH conversion efficiency by its large second-order nonlinear coefficient. Conventional LiNbO3 devices require long interaction lengths and meet phase matching requirements. Thin-film lithium niobium oxide enables better optical mode confinement and improves SH conversion efficiency. A distributed Bragg reflection trapezoidal grating SHconversion device based on quasi-bound states of continuous LiNbO3 thin films is designed. The device can generate narrow-band resonances with five high Q-factors over a broadband width of 500-800 nm. Based on the multistage expansion algorithm and the magnetic field map obtained by simulation, a suitable resonant mode is selected to obtain a higher SH generation efficiency. By rationally designing the structural parameters of the device as well as the incident light intensity, a high SH generation efficiency of up to 3.35 x 10-3 can be obtained. As a result, our devices are designed for high efficiency, low loss and multi-band SH generation devices.
For given two digraphs,we can construct a larger digraph through *** two digraphs that make up the join are called the factors of the *** this paper,we give a necessary and sufficient condition that the function on th...
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For given two digraphs,we can construct a larger digraph through *** two digraphs that make up the join are called the factors of the *** this paper,we give a necessary and sufficient condition that the function on the join determined by the discrete Morse functions on factors is a discrete Morse ***,we further prove the discrete Morse theory on join when the factors satisfy certain conditions.
In 2004, graphene was discovered by Novoselov and Geim. With the development of technology?twisted bilayer graphene (tBLG) has become a hot research topic. On the basis of predecessors, we further study the confined s...
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In 2004, graphene was discovered by Novoselov and Geim. With the development of technology?twisted bilayer graphene (tBLG) has become a hot research topic. On the basis of predecessors, we further study the confined spaces between twisted bilayer graphene. The interlayer spacing between them is expected to modify properties of atoms and molecules confined at the atomic interfaces. The effects of twist angle, interlayer spacing of the tBLG and temperature (20 K-70 K) on the equilibrium structure of argon cluster are systematically studied by means of molecular dynamics simulation with the tBLG being considered to be fixed. As the interlayer spacings of tBLGs with different twist angles increase at a fixed temperature 20 K, the equilibrium structures of the argon cluster transform from a monoatomic layer to multilayer structure. For different twist angles at the fixed interlayer spacing, the structures of the argon cluster gradually form periodic pattern (similar to moire pattern). The effects of temperature and non-equiliblium suddenly heating process on the structures of argon clusters between tBLGs are also studied by molecular dynamics simulation. Our results may provide a theoretical support for the preparation of new carbon-based intercalated composites and the application of graphene.
With the depletion of shallow metal mineral resources, deep mining has become more common. In the process of deep mining, heat hazards in mines seriously threaten the health of personnel and the safety of mining opera...
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With the depletion of shallow metal mineral resources, deep mining has become more common. In the process of deep mining, heat hazards in mines seriously threaten the health of personnel and the safety of mining operations. According to the flow and low-temperature characteristics of abundant water in Maoping Lead Zinc Mine, this paper proposes the direct use of the low-temperature water inflow of the mine as the cold source by which to conduct the heat exchange with a single spiral-tube heat exchanger for mine cooling. An experimental platform was built for the cooling system to allow us to explore the mechanism of the influence of the inlet air volume and air temperature and the inlet water temperature and flow on the cooling effect of the single spiral-tube heat exchanger. It was found that with the increase in the inlet air volume and inlet water temperature, the cooling efficiency of the heat exchanger decreased, while with the increase in the inlet air temperature, the cooling efficiency of the heat exchanger increased. Within the experimental range, 127.2 m(3)/h was found to be the optimum inlet air volume, and 33.0 degrees C was the most appropriate inlet air temperature;the water temperature of Maoping Coal Mine is about 20 degrees C throughout the year, and the industrial test site can reduce the wind temperature of 31.5 degrees C to 23.9 degrees C. The inlet water flow is positively related to the cooling effect. With the increase in the water flow, the outlet temperature of the air flow at each working point was continuously reduced, and the cooling effect of the heat exchanger was improved. The moisture content of the inlet air flow can be reduced by increasing the low-temperature inlet water flow. Through experiments, the feasibility of the cooling system that directly uses the mine's low-temperature water as the cold source was verified. A multiple linear regression analysis equation for the cooling system model is proposed, which provides a reference
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