文章结合数学知识由单摆模型迁移研究椭圆摆模型发现微幅椭圆摆做简谐运动,但决定其简谐运动角振幅的物理量不是中心摆角,而是由切向角和参数角共同决定,并得出定量关系式:b/a<1,由参数角决定,须参数角不大于5°,对应的最大中心...文章结合数学知识由单摆模型迁移研究椭圆摆模型发现微幅椭圆摆做简谐运动,但决定其简谐运动角振幅的物理量不是中心摆角,而是由切向角和参数角共同决定,并得出定量关系式:b/a<1,由参数角决定,须参数角不大于5°,对应的最大中心角为arctan(a/b tan 5°)>5°;b/a>1,由切向角决定,须切向角不大于5°,对应的最大中心角为arctan(a^(2)/b^(2) tan 5°)≈a^(2)/b^(2)·5°<5°,最大参数角为arctan(a/b·tan 5°)≈a/b·5°<5°。最后用数学软件绘制了周期与初始参数角的函数图象并进行了误差分析,有力地佐证了这一结论。展开更多
To solve the heat dissipation problem of electronic devices with high heat flux hotspots,a diamond microchannel heat sink consisting of 37 parallel triangular microchannels with channel lengths of 45 mm and hydraulic ...To solve the heat dissipation problem of electronic devices with high heat flux hotspots,a diamond microchannel heat sink consisting of 37 parallel triangular microchannels with channel lengths of 45 mm and hydraulic diameters of 280|im was designed.The flow boiling heat transfer characteristics of ammonia in the microchannels were investigated under high heat fluxes of 473.9-1000.4 W/cm^2.Saturated flow boiling experiments with saturation temperatures of 25℃,30℃,and 35℃ and mass fluxes of 98-1200 kg/m^2s were conducted,as well as subcooled flow boiling with inlet subcooling of 5℃ as a comparison.The temperature and pressure drop measurements were analyzed.The main conclusions below can be drawn.(1)At a given heat flux,the heat source temperature first decreased and then increased with the mass flux,and there existed an optimum mass flux to optimize the cooling performance of the heat sink.(2)The heat transfer performance under the saturated inlet condition was obviously better than that under the subcooled inlet condition.(3)A larger saturation temperature leaded to weakening of both the heat transfer capacity and the stability of the microchannel heat sink.Notably,with the high heat diffusion ability of the diamond substrate and the great heat transfer capacity of ammonia flow boiling in microchannels,the heat sink can achieve a heat removal capacity of up to 1000.4 W/cm^2.展开更多
On May 21,2023,the Macao Science Satellite-1B(MSS-1B),a low-inclination,low-latitude,and high-precision scientific exploration satellite for geomagnetic fields and space environments,was successfully launched.The sola...On May 21,2023,the Macao Science Satellite-1B(MSS-1B),a low-inclination,low-latitude,and high-precision scientific exploration satellite for geomagnetic fields and space environments,was successfully launched.The solar X-ray detector(SXD),one of the two major scientific payloads onboard the MSS-1B,has obtained a large amount of solar X-ray radiation data,which reveals the distribution law of the magnetic field in the low Earth orbit,as well as the coupling law of the Earth's magnetic field and the solar radiation and energy particle distributions.First,the overall design of the multi-detection-unit,broad-energy-range,small-volume,and low-power SXD was implemented to achieve the scientific objectives of the mission.Second,the technical indicators of the instrument were decomposed into various components,and the key technologies,such as collimator,processing circuit,thermal,and payload dataset designs,were reviewed.Third,the backgrounds,including electronic noise,cosmic diffuse X-ray background,and high-energy background in the Earth's radiation belts in and out of the field of view,were analyzed for the instrument.Then,the ground calibrations of the energy response,detection efficiency,and temperature-dependent peak drift of the SXD flight model were conducted.Finally,the in-orbit temperature,energy spectrum data,background,and solar flare process observation of the instrument in the in-orbit test stage are presented,verifying the instrument design,analysis,and ground calibration,providing a foundation for obtaining accurate solar X-ray radiation data,and achieving the scientific objectives of the satellite.展开更多
文摘文章结合数学知识由单摆模型迁移研究椭圆摆模型发现微幅椭圆摆做简谐运动,但决定其简谐运动角振幅的物理量不是中心摆角,而是由切向角和参数角共同决定,并得出定量关系式:b/a<1,由参数角决定,须参数角不大于5°,对应的最大中心角为arctan(a/b tan 5°)>5°;b/a>1,由切向角决定,须切向角不大于5°,对应的最大中心角为arctan(a^(2)/b^(2) tan 5°)≈a^(2)/b^(2)·5°<5°,最大参数角为arctan(a/b·tan 5°)≈a/b·5°<5°。最后用数学软件绘制了周期与初始参数角的函数图象并进行了误差分析,有力地佐证了这一结论。
文摘To solve the heat dissipation problem of electronic devices with high heat flux hotspots,a diamond microchannel heat sink consisting of 37 parallel triangular microchannels with channel lengths of 45 mm and hydraulic diameters of 280|im was designed.The flow boiling heat transfer characteristics of ammonia in the microchannels were investigated under high heat fluxes of 473.9-1000.4 W/cm^2.Saturated flow boiling experiments with saturation temperatures of 25℃,30℃,and 35℃ and mass fluxes of 98-1200 kg/m^2s were conducted,as well as subcooled flow boiling with inlet subcooling of 5℃ as a comparison.The temperature and pressure drop measurements were analyzed.The main conclusions below can be drawn.(1)At a given heat flux,the heat source temperature first decreased and then increased with the mass flux,and there existed an optimum mass flux to optimize the cooling performance of the heat sink.(2)The heat transfer performance under the saturated inlet condition was obviously better than that under the subcooled inlet condition.(3)A larger saturation temperature leaded to weakening of both the heat transfer capacity and the stability of the microchannel heat sink.Notably,with the high heat diffusion ability of the diamond substrate and the great heat transfer capacity of ammonia flow boiling in microchannels,the heat sink can achieve a heat removal capacity of up to 1000.4 W/cm^2.
基金supported by the National Natural Science Foundation of China(Grant No.42327802)the National Key R&D Program of China(Grant No.2022YFF0708100)。
文摘On May 21,2023,the Macao Science Satellite-1B(MSS-1B),a low-inclination,low-latitude,and high-precision scientific exploration satellite for geomagnetic fields and space environments,was successfully launched.The solar X-ray detector(SXD),one of the two major scientific payloads onboard the MSS-1B,has obtained a large amount of solar X-ray radiation data,which reveals the distribution law of the magnetic field in the low Earth orbit,as well as the coupling law of the Earth's magnetic field and the solar radiation and energy particle distributions.First,the overall design of the multi-detection-unit,broad-energy-range,small-volume,and low-power SXD was implemented to achieve the scientific objectives of the mission.Second,the technical indicators of the instrument were decomposed into various components,and the key technologies,such as collimator,processing circuit,thermal,and payload dataset designs,were reviewed.Third,the backgrounds,including electronic noise,cosmic diffuse X-ray background,and high-energy background in the Earth's radiation belts in and out of the field of view,were analyzed for the instrument.Then,the ground calibrations of the energy response,detection efficiency,and temperature-dependent peak drift of the SXD flight model were conducted.Finally,the in-orbit temperature,energy spectrum data,background,and solar flare process observation of the instrument in the in-orbit test stage are presented,verifying the instrument design,analysis,and ground calibration,providing a foundation for obtaining accurate solar X-ray radiation data,and achieving the scientific objectives of the satellite.
