Subjects: Other Disciplines >> Synthetic discipline submitted time 2023-03-28 Cooperative journals: 《中国科学院院刊》
Abstract： The key issues to achieve the “dual carbon” goals mainly involve three aspects: the structure of energy and power supply, the development of energy storage technology and the construction of new power system. Combined with the specific situation of China, this study analyzes and forecasts the power supply structure dominated by renewable energy; Considering the characteristics and development needs of renewable energy, the viewpoint and idea are put forward to develop physical energy storage, especially underground energy storage engineering, to meet the large-scale energy storage needs of power grid. On this basis, the overall idea is suggested for constructing wide area virtual power plant and future power system.
Subjects: Other Disciplines >> Synthetic discipline submitted time 2023-03-28 Cooperative journals: 《中国科学院院刊》
Abstract： Under the ‘carbon peak and carbon neutrality’ goal, the supply and demand of China’s power system will continue to grow in the next 40 years. Firstly, this study comprehensively analyzes China’s power grid system under the goal of carbon neutralization. In the future, wind power and solar power will gradually become the main power supply, which brings new tasks and challenges to the power grid to absorb the renewable energy. On this basis, the general idea and construction principles of building a new generation of power system are expounded. Then, the basic structure and form of the new generation of power system are analyzed. Due to the continuous expansion of long#2;distance transmission scale and the imbalance of resources and load in the future, thenew generation of power system still has the remarkable characteristics of reverse distribution between the power supply and the load. Therefore, its basic form is still composed of large power and effectively supplemented by distributed power system. In addition, the flexible regulation of resources in the power grid is very important for the safe operation of the power grid, the power market operation mechanism should guide multiple subjects to participate in the construction of the new generation of power system. Finally, the phased implementation strategy of building a new power system for carbon neutralization is proposed, which has an important guiding role on building the new power system and realizing carbon neutralization.
Subjects: Other Disciplines >> Synthetic discipline submitted time 2023-03-28 Cooperative journals: 《中国科学院院刊》
Abstract： China has a vast geographical area and abundant solar energy and wind energy resources, which are sufficient to meet the needs of China’s social production and life. After decades of development, solar photovoltaic power generation and wind power generation technologies have matured, the scale of industries and applications has developed rapidly, and power generation has continued to grow. It has become an important clean power source in the world. The cost of solar and wind power generation is rapidly declining, driven by technological advances and the expansion of the market, and in the foreseeable future solar photovoltaic and wind power generation will be technically and economically equivalent to conventional energy sources, that will promote energy transformation.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract： Micro-computed tomography is a new three-dimension high-resolution imaging device, which due to its X-ray brightness generated by a compact electron impact X-ray source. To achieve higher X-ray brightness, the size of the X-ray source should be as small as possible. However, the X-ray brightness is fundamentally limited by the maximum possible heat dissipation of the X-ray target. As an electron beam strikes a metallic target, the power density of target is increased with the decreasing of the spot size of electron beam, which results in the decre ase of the X-ray brightness by significant temperature elevation of the target surface. A practical solution for these requirements is the use of a multi-film target consisting of a thin-film target on a thicker substrate film. The substrate should be composed of a light material with high thermal conductivity to prevent absorption of the signal X-rays and to elevate the target temperature. In such a multi-film target, several factors as following must be considered to choose the materials and thicknesses of the multiple films: the highest power density of the target can sustain without performance degradations or damage, and the efficiency of the X-ray generation in the target material including any self absorption effects. The present work designed a basic structure of tungsten-aluminum transmission target, according to the theoretical model of the end-window transmission target for Micro-CT. The thicknesses of tungsten target surface and aluminum substrate are determined by the Geant4 simulation results and the Müller calculation model of temperature rise, respectively. According to the structure parameter of tungsten-aluminum transmission target of YXLON, the tungsten film with the thickness of 2, 5 and 8 μm are prepared on the aluminum substrate by the magnetron sputtering method. The density and evenness of tungsten film both are well by the SEM analysis. The performance of three kinds of target with different thicknesses is carried out on the X-ray tube of YXLON. The results show that the optimal thickness of tungsten film is 5 mm, and the X-ray emitting efficiency of tungsten-aluminum transmission target is the biggest, which the corresponding production power of Xray is the lowest. On this basis, the contrast experiments of X-ray emitting efficiency and X-ray imaging effect are carried out between the tungsten-aluminum transmission target of homemade and that of YXLON. The experimental results indicate that the X-ray emitting efficiency, the corresponding X-ray production power and the X-ray imaging effect of homemade target all are superior to that of YXLON, which could be satisfied the application requirements of high quality target for Micro-CT.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract： Directional solidification of Al-4.5Cu alloy refined by adding Al-5Ti-1B has been carried out to investigate the texture formation and grain boundary characteristic of the paramagnetic crystal under a high magnetic field. OM and EBSD were applied to analyze the microstructures solidified at different temperature gradients (G) and magnetic field intensities (B). The results show that at the temperature gradient of 27 K/cm, the orientations of fcc a-Al grains without magnetic field are random. However, as a high magnetic field is imposed, the easy magnetization axes〈310〉of the a-Al grains are aligned parallel to the direction of the magnetic field leading to〈310〉texture. Meanwhile, the ratio of coincidence site lattice (CSL) grain boundaries increases with the increment of magnetic field intensity and reaches its maximum value at 4 T, but decreases as the magnetic field enhances further. On the other hand, when the temperature gradient is elevated, columnar dendrite morphology is exhibited without magnetic field; while a 6 T high magnetic field is introduced, the columnar dendrites are broken and equiaxed grains of random orientations are obtained. The alignment behavior of the free crystals in melt could be attributed to the magnetic crystalline anisotropy of a-Al. Moreover, the influence of fluid flow on the texture formation and CSL grain boundary development under magnetic field is discussed. The absence of convection is benefit for grain reorientation and CSL boundary formation. The application of high static magnetic field will inhibit the macro-scale convection. However, the interaction between thermoelectric current and magnetic field will cause micro-scale fluid flow, i.e., thermoelectric magnetic convection (TEMC). The TEMC will give rise to perturbation near the solid-liquid interface leading to the appearance of freckles as well as the decreasing of the ratio of CSL boundary. Moreover, it is proposed that the formation of CSL boundary is associated with the rotation of the free grains in melt along specific crystallographic axes by magnetic torque.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract： Micro-computed tomography is a new three-dimension high-resolution imaging device, which due to its X-ray brightness generated by a compact electron impact X-ray source. To achieve higher X-ray brightness, the size of the X-ray source should be as small as possible. However, the X-ray brightness is fundamentally limited by the maximum possible heat dissipation of the X-ray target. As an electron beam strikes a metallic target, the power density of target is increased with the decreasing of the spot size of electron beam, which results in the decrease of the X-ray brightness by significant temperature elevation of the target surface. A practical solution for these requirements is the use of a multi-film target consisting of a thin-film target on a thicker substrate film. The substrate should be composed of a light material with high thermal conductivity to prevent absorption of the signal X-rays and to elevate the target temperature. In such a multi-film target, several factors as following must be considered to choose the materials and thicknesses of the multiple films: the highest power density of the target can sustain without performance degradations or damage, and the efficiency of the X-ray generation in the target material including any self absorption effects. The present work designed a basic structure of tungsten-aluminum transmission target, according to the theoretical model of the end-window transmission target for Micro-CT. The thicknesses of tungsten target surface and aluminum substrate are determined by the Geant4 simulation results and the Müller calculation model of temperature rise, respectively. According to the structure parameter of tungsten-aluminum transmission target of YXLON, the tungsten film with the thickness of 2, 5 and 8 μm are prepared on the aluminum substrate by the magnetron sputtering method. The density and evenness of tungsten film both are well by the SEM analysis. The performance of three kinds of target with different thicknesses is carried out on the X-ray tube of YXLON. The results show that the optimal thickness of tungsten film is 5 mm, and the X-ray emitting efficiency of tungsten-aluminum transmission target is the biggest, which the corresponding production power of Xray is the lowest. On this basis, the contrast experiments of X-ray emitting efficiency and X-ray imaging effect are carried out between the tungsten-aluminum transmission target of homemade and that of YXLON. The experimental results indicate that the X-ray emitting efficiency, the corresponding X-ray production power and the X-ray imaging effect of homemade target all are superior to that of YXLON, which could be satisfied the application requirements of high quality target for Micro-CT.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-18 Cooperative journals: 《材料研究学报》
Abstract： Si3N4 ceramics with preferential texture along a or b axis were shaped up by gel-casting in a magnetic field of 6T and then pressureless sintered. Effect of the sintering temperature and time on the texture formation of the Si3N4 ceramics was investigated. It was found that the phase transformation of α to β was completed for the Si3N4 ceramics prepared by the present process. With the increasing sintering temperature the texture formation of Si3N4 ceramics may be enhanced, i.e. of which the degree of texture increased from 0.40 at 1700℃ to 0.76 at 1800℃. The extension of sintering time at 1750℃ had few effect on texture development of Si3N4 ceramics.
Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics submitted time 2020-10-12
Abstract： This paper describes a research that studied the current characteristics of REBCO tapes in liquid nitrogen after heat treatment at different temperatures. The reason of the deterioration at high temperature is briefly introduced. The conclusion presented in this paper is instructive for the winding of superconducting coils and the fabrication of superconducting magnets. "
Peer Review Status:
Awaiting Review
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2017-03-22 Cooperative journals: 《工程热物理学报》
Abstract：本文基于平板微热管阵列技术，提出了一种太阳能空气集热、蓄热一体化装置，阐明了该装置的结构和工作原理。本装置以平板微热管阵列为关键热输送部件，采用52#石蜡作为相变储热材料，搭建了该一体化装置性能研究试验系统，对该装置蓄热器内部石蜡温度变化、蓄放热效率及蓄放热功率进行了实验研究和分析。结果表明：太阳能集热蓄热一体化装置可高效稳定运行，实测集/蓄、放热性能优良，测试工况下平均蓄/放热效率为59%/91.6%，平均蓄/放热功率为393W/344W。
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