分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: Neural networks have provided powerful approaches to solve various scientific problems. Many of them are even difficult for human experts who are good at accessing the physical laws from experimental data. We investigate whether neural networks can assist us in exploring the fundamental laws of classical mechanics from data of planetary motion. Firstly, we predict the orbits of planets in the geocentric system using the gate recurrent unit, one of the common neural networks. We find that the precision of the prediction is obviously improved when the information of the Sun is included in the training set. This result implies that the Sun is particularly important in the geocentric system without any prior knowledge, which inspires us to gain Copernicus' heliocentric theory. Secondly, we turn to the heliocentric system and make successfully mutual predictions between the position and velocity of planets. We hold that the successful prediction is due to the existence of enough conserved quantities (such as conservations of mechanical energy and angular momentum) in the system. Our research provides a new way to explore the existence of conserved quantities in mechanics system based on neural networks.
分类: 物理学 >> 交叉学科物理及相关领域的科学与技术 提交时间: 2018-03-30
摘要: AgSbTe2 bulk sample is obtained by hot-pressing under different fabrication parameters, and their thermoelectric properties are investigated in the temperature range of 300-550K. The highest ZT=0.86 is achieved at 475K for the sample hot-pressed at 423K and 500MPa due to the lower thermal conductivity and higher power factor. The results indicate that the optimized thermoelectric properties can be obtained for AgSbTe2 compound at the sintering temperature of 423K under the pressure of 500MPa.
分类: 物理学 >> 交叉学科物理及相关领域的科学与技术 提交时间: 2018-03-30
摘要: Gd-doped compounds CuGa1-xGdxTe2 (0x0.02) incorporated with tellurium nanoparticles are synthesized by fusion method. Their thermoelectric properties are investigated in the temperature range of 300-800K. The results indicate that the synergistic effect of Gd-doping and Te incorporation remarkably enhances the thermoelectric performance of CuGaTe2. Specially, the thermal conductivity of the specimen CuGa0.98Gd0.02Te2/0.7vol.%Te reduces to 0.45 Wm-1K-1 at 684K, which is ~74% smaller than that of pure CuGaTe2 (=1.76 Wm-1K-1 at 684K) due to the incorporation of nanostructure Te. The thermoelectric figure of merit value (ZT) reaches 0.75 at 737K for the specimen CuGa0.99Gd0.01Te2/0.7vol.%Te, which is ~115% larger than that of pure CuGaTe2.
分类: 物理学 >> 交叉学科物理及相关领域的科学与技术 提交时间: 2018-03-30
摘要: CuGaTe2 based composites incorporated with graphite nanosheets(GNs) CuGaTe2/x G (G=GNs, 0x3.04 vol.%) were prepared, and the thermoelectric properties of the composites were studied from 300 to 875 K. The results show that the incorporation of GNs into the CuGaTe2 matrix can enhance the Seebeck coefficient and power factor over the whole temperature range investigated due to energy filtering effects, and the reduction of thermal conductivity below 750K owing to interface scattering. Although the resistivity increases, energy filtering significantly raises the Seebeck component, and the overall effect on power factor is positive. The sample with 2.28 vol.% GNs had the largest ZT value, reaching 0.93 at 873K, which is a ~21% improvement on pure CuGaTe2.