The regional BeiDou Satellite System, or BDS2, broadcasts a differential correction as Equivalent Satellite Clock Correction to correct both orbit and satellite clock errors. For the global BDS, or BDS3, satellite orb...The regional BeiDou Satellite System, or BDS2, broadcasts a differential correction as Equivalent Satellite Clock Correction to correct both orbit and satellite clock errors. For the global BDS, or BDS3, satellite orbit and clock corrections conforming with RTCA standards will be broadcast to authorized users. The hybrid constellation and regional monitoring network pose challenges for the high precision separation of orbit and satellite clock corrections. Three correction models of kinematic,dynamic and Two-way Satellite Time Frequency Transfer(TWSTFT)-based dynamic were studied to estimate the satellite orbit and clock corrections. The correction accuracy of the three models is compared and analyzed based on the BDS observation data. Results show that the accuracies(root mean square, RMS) of dual-frequency real-time positioning for the three models are about 1.76 m, 1.78 m and 2.08 m respectively, which are comparable with the performance of WAAS and EGNOS. With dynamic corrections, the precision of Precise Point Positioning(PPP) experiments may reach about 23 cm after convergence.展开更多
Accident-tolerant fuels(ATF)have been extensively studied to reduce the production rate and total amount of heat and hydrogen generated from high-temperature steam oxidation during severe accidents.Chromium-coated zir...Accident-tolerant fuels(ATF)have been extensively studied to reduce the production rate and total amount of heat and hydrogen generated from high-temperature steam oxidation during severe accidents.Chromium-coated zirconium alloy cladding has become one of the most promising candidates for ATF because of its excellent corrosion and oxidation resistance.This paper provides a comprehensive overview of the research progress on oxidation behaviors and degradation mechanisms in chromium-coated zirconium alloy cladding under high-temperature conditions.Potential techniques to strengthen the oxidation resistance are highlighted and compared.Finally,challenges and opportunities for various future directions are addressed.展开更多
Tungsten(W),as a plasma-facing material,is subjected to high fluence plasma,resulting in both radiation damage and deuterium(D)retention.This study explores the blistering behavior and D supersaturated layers in both ...Tungsten(W),as a plasma-facing material,is subjected to high fluence plasma,resulting in both radiation damage and deuterium(D)retention.This study explores the blistering behavior and D supersaturated layers in both pre-damaged and undamaged W samples.To achieve a uniform damage profile similar to neutron irradiation,carbon(C)ions with multiple energies and angles were employed.The samples were further irradiated with low-energy D ions under two fluences at temperatures from~380 to 640 K.Using various experimental techniques,we found that pre-damaged W samples can effectively suppress the formation of blistering and lower the threshold temperature at which the surface remains free of blistering.We also observed the prominent D supersaturated peaks within the depth of 20 nm in both pre-damaged and undamaged W.Furthermore,a close correlation between blistering and the D supersaturation was investigated.The results suggest that neutron irradiation in the fusion reactors could increase the critical D concentration for blistering,while a greater depth of damage facilitated the inward diffusion of D,thereby reducing the D concentration gradient and alleviating surface blistering.展开更多
基金supported by the National Key Research Program of China as the“Collaborative Precision Positioning Project”(No.2016YFB0501900)the National Natural Science Foundation of China(Grant Nos.41674041,41574029 and 11203059)+2 种基金the Youth Innovation Promotion Association CAS(Grant No.2016242)Shanghai Science and Technology Committee Foundation(Grant No.16511103003)the Shanghai Key Laboratory of Space Navigation and Position Techniques(Grant No.12DZ2273300,ZZXT201701)
文摘The regional BeiDou Satellite System, or BDS2, broadcasts a differential correction as Equivalent Satellite Clock Correction to correct both orbit and satellite clock errors. For the global BDS, or BDS3, satellite orbit and clock corrections conforming with RTCA standards will be broadcast to authorized users. The hybrid constellation and regional monitoring network pose challenges for the high precision separation of orbit and satellite clock corrections. Three correction models of kinematic,dynamic and Two-way Satellite Time Frequency Transfer(TWSTFT)-based dynamic were studied to estimate the satellite orbit and clock corrections. The correction accuracy of the three models is compared and analyzed based on the BDS observation data. Results show that the accuracies(root mean square, RMS) of dual-frequency real-time positioning for the three models are about 1.76 m, 1.78 m and 2.08 m respectively, which are comparable with the performance of WAAS and EGNOS. With dynamic corrections, the precision of Precise Point Positioning(PPP) experiments may reach about 23 cm after convergence.
基金financially supported by the LingChuang Research Project of China National Nuclear Corporation(CNNC-LCKY-202242)。
文摘Accident-tolerant fuels(ATF)have been extensively studied to reduce the production rate and total amount of heat and hydrogen generated from high-temperature steam oxidation during severe accidents.Chromium-coated zirconium alloy cladding has become one of the most promising candidates for ATF because of its excellent corrosion and oxidation resistance.This paper provides a comprehensive overview of the research progress on oxidation behaviors and degradation mechanisms in chromium-coated zirconium alloy cladding under high-temperature conditions.Potential techniques to strengthen the oxidation resistance are highlighted and compared.Finally,challenges and opportunities for various future directions are addressed.
基金supported by the National Key R&D Program of China(Grant No.2017YFA0402503)。
文摘Tungsten(W),as a plasma-facing material,is subjected to high fluence plasma,resulting in both radiation damage and deuterium(D)retention.This study explores the blistering behavior and D supersaturated layers in both pre-damaged and undamaged W samples.To achieve a uniform damage profile similar to neutron irradiation,carbon(C)ions with multiple energies and angles were employed.The samples were further irradiated with low-energy D ions under two fluences at temperatures from~380 to 640 K.Using various experimental techniques,we found that pre-damaged W samples can effectively suppress the formation of blistering and lower the threshold temperature at which the surface remains free of blistering.We also observed the prominent D supersaturated peaks within the depth of 20 nm in both pre-damaged and undamaged W.Furthermore,a close correlation between blistering and the D supersaturation was investigated.The results suggest that neutron irradiation in the fusion reactors could increase the critical D concentration for blistering,while a greater depth of damage facilitated the inward diffusion of D,thereby reducing the D concentration gradient and alleviating surface blistering.
