We investigate the 2005 August 22 flare event（00：54 UT） exploiting hard X-ray（HXR） observations from the Reuven Ramaty High Energy Solar Spectroscopic Imager（RHESSI） and microwave（MW） observations from the No...We investigate the 2005 August 22 flare event（00：54 UT） exploiting hard X-ray（HXR） observations from the Reuven Ramaty High Energy Solar Spectroscopic Imager（RHESSI） and microwave（MW） observations from the Nobeyama Solar Radio Observatory. The HXR time profile exposes well-damped quasi-periodic pulsations with four sequential peaks, and the MW time profile follows the corresponding peaks.Based on this feature, we derive the time relationship of HXRs and MWs with multifrequency data from the Nobeyama Radio Polarimeter, and the spatially resolvable data from RHESSI and the Nobeyama Radioheliograph. We find that both frequency dependent delays in MWs and energy dependent delays in HXRs are significant.Furthermore, MW emissions from the south source are delayed with respect to those from the north source at both 17 GHz and 34 GHz, but no significant delays are found in HXR emissions from the different sources at the same energies. To better understand all these long time delays, we derive the electron fluxes of different energies by fitting the observed HXR spectra with a single power-law thick-target model, and speculate that these delays might be related to an extended acceleration process. We further compare the time profile of a MW spectral index derived from 17 and 34 GHz fluxes with the flux densities, and find that the spectral index shows a strong anticorrelation with the HXR fluxes.展开更多
Quantum communication is a groundbreaking technology that is driving the future of information transmission and communication technologies to a new paradigm.It relies on quantum entanglement to facilitate the transmis...Quantum communication is a groundbreaking technology that is driving the future of information transmission and communication technologies to a new paradigm.It relies on quantum entanglement to facilitate the transmission of quantum states between parties.Quantum repeaters are crucial for facilitating long-distance quantum communication.These quantum devices act as intermediaries between adjacent communication channel segments within a fragmented quantum network,allowing for entanglement swapping between the channel segments.This entanglement swapping process establishes entanglement links between the endpoints of adjacent segments,gradually creating a continuous entanglement connection over the entire length of the transmission channel.The established quantum link can be utilized for secure and efficient quantum communication between distant sender and receiver nodes.This study focuses on quantum entanglement purification,a protocol aimed at maintaining high fidelity entangled states above the operational threshold of the communication channel.This study investigates the optimal stage for executing the purification protocol and applies optimization schemes to evaluate various purification protocols.We use IBM Qiskit for circuit implementation and simulation.The results offer valuable insights into future approaches to implementing practical quantum repeaters and shed light on existing and anticipated challenges.展开更多
CubeSats have become versatile platforms for various space missions(e.g.,on-orbit servicing and debris removal)owing to their low cost and flexibility.Many space tasks involve proximity operations that require precise...CubeSats have become versatile platforms for various space missions(e.g.,on-orbit servicing and debris removal)owing to their low cost and flexibility.Many space tasks involve proximity operations that require precise guidance,navigation,and control(GNC)algorithms.Vision-based navigation is attracting interest for such operations.However,extreme lighting conditions in space challenge optical techniques.The on-ground validation of such navigation systems for orbital GNC becomes crucial to ensure their reliability during space operations.These systems undergo rigorous testing within their anticipated operational parameters,including the exploration of potential edge cases.The ability of GNC algorithms to function effectively under extreme space conditions that exceed anticipated scenarios is crucial,particularly in space missions where the scope of errors is negligible.This paper presents the ground validation of a GNC algorithm designed for autonomous satellite rendezvous by leveraging hardware-in-the-loop experiments.This study focuses on two key areas.First,the rationale underlying the augmentation of the robot workspace(six-degree-of-freedom UR10e robot+linear rail)is investigated to emulate relatively longer trajectories with complete position and orientation states.Second,the control algorithm is assessed in response to uncertain pose observations from a vision-based navigation system.The results indicate increased control costs with uncertain navigation and exemplify the importance of on-ground testing for system validation before launch,particularly in extreme cases that are typically difficult to assess using software-based testing.展开更多
基金Supported by the National Natural Science Foundation of China
文摘We investigate the 2005 August 22 flare event（00：54 UT） exploiting hard X-ray（HXR） observations from the Reuven Ramaty High Energy Solar Spectroscopic Imager（RHESSI） and microwave（MW） observations from the Nobeyama Solar Radio Observatory. The HXR time profile exposes well-damped quasi-periodic pulsations with four sequential peaks, and the MW time profile follows the corresponding peaks.Based on this feature, we derive the time relationship of HXRs and MWs with multifrequency data from the Nobeyama Radio Polarimeter, and the spatially resolvable data from RHESSI and the Nobeyama Radioheliograph. We find that both frequency dependent delays in MWs and energy dependent delays in HXRs are significant.Furthermore, MW emissions from the south source are delayed with respect to those from the north source at both 17 GHz and 34 GHz, but no significant delays are found in HXR emissions from the different sources at the same energies. To better understand all these long time delays, we derive the electron fluxes of different energies by fitting the observed HXR spectra with a single power-law thick-target model, and speculate that these delays might be related to an extended acceleration process. We further compare the time profile of a MW spectral index derived from 17 and 34 GHz fluxes with the flux densities, and find that the spectral index shows a strong anticorrelation with the HXR fluxes.
文摘Quantum communication is a groundbreaking technology that is driving the future of information transmission and communication technologies to a new paradigm.It relies on quantum entanglement to facilitate the transmission of quantum states between parties.Quantum repeaters are crucial for facilitating long-distance quantum communication.These quantum devices act as intermediaries between adjacent communication channel segments within a fragmented quantum network,allowing for entanglement swapping between the channel segments.This entanglement swapping process establishes entanglement links between the endpoints of adjacent segments,gradually creating a continuous entanglement connection over the entire length of the transmission channel.The established quantum link can be utilized for secure and efficient quantum communication between distant sender and receiver nodes.This study focuses on quantum entanglement purification,a protocol aimed at maintaining high fidelity entangled states above the operational threshold of the communication channel.This study investigates the optimal stage for executing the purification protocol and applies optimization schemes to evaluate various purification protocols.We use IBM Qiskit for circuit implementation and simulation.The results offer valuable insights into future approaches to implementing practical quantum repeaters and shed light on existing and anticipated challenges.
基金supported by the Luxembourg National Research Fund:INTER20/EUROSTARS/15254521/VBN/Olivares Mendez.The project,E115088-VBN,has received funding from the Eurostars-2 Joint Programme with cofunding from the European Union’s Horizon 2020 Research and Innovation Programme.
文摘CubeSats have become versatile platforms for various space missions(e.g.,on-orbit servicing and debris removal)owing to their low cost and flexibility.Many space tasks involve proximity operations that require precise guidance,navigation,and control(GNC)algorithms.Vision-based navigation is attracting interest for such operations.However,extreme lighting conditions in space challenge optical techniques.The on-ground validation of such navigation systems for orbital GNC becomes crucial to ensure their reliability during space operations.These systems undergo rigorous testing within their anticipated operational parameters,including the exploration of potential edge cases.The ability of GNC algorithms to function effectively under extreme space conditions that exceed anticipated scenarios is crucial,particularly in space missions where the scope of errors is negligible.This paper presents the ground validation of a GNC algorithm designed for autonomous satellite rendezvous by leveraging hardware-in-the-loop experiments.This study focuses on two key areas.First,the rationale underlying the augmentation of the robot workspace(six-degree-of-freedom UR10e robot+linear rail)is investigated to emulate relatively longer trajectories with complete position and orientation states.Second,the control algorithm is assessed in response to uncertain pose observations from a vision-based navigation system.The results indicate increased control costs with uncertain navigation and exemplify the importance of on-ground testing for system validation before launch,particularly in extreme cases that are typically difficult to assess using software-based testing.
