The emission of anomalous X-ray pulsars(AXPs)and soft gamma-ray repeaters(SGRs)is believed to be powered by the dissipation of their strong magnetic fields,which coined the name“magnetar”.By combining timing and ene...The emission of anomalous X-ray pulsars(AXPs)and soft gamma-ray repeaters(SGRs)is believed to be powered by the dissipation of their strong magnetic fields,which coined the name“magnetar”.By combining timing and energy observational results,the magnetar model can be easily appreciated.From a timing perspective,the magnetic field strengths of AXPs and SGRs,which are calculated under the assumption of dipole radiation,are extremely strong.From an energy perspective,the X-ray/soft gamma-ray luminosities of AXPs and SGRs are larger than their rotational energy loss rates(i.e.,L_(x>E_(rot)).It is thus reasonable to assume that the high-energy radiation comes from magnetic energy decay,and the magnetar model has been extensively discussed(or accepted).However,we argue that:(ⅰ)Calculating magnetic fields by assuming that rotational energy loss is dominated by dipole radiation(i.e.,E_(rot)■E_(μ))may be controversial,and we suggest that the energies carried by outflowing particles should also be considered.(ⅱ)The fact that X-ray luminosity is greater than the rotational energy loss rate does not necessarily mean that the emission energy comes from the magnetic field decaying,which requires further observational testing.Furthermore,some observational facts conflict with the“magnetar”model,such as observations of anti-magnetars,high magnetic field pulsars,and radio and X-ray observations of AXPs/SGRs.Therefore,we propose a crusted strange star model as an alternative,which can explain many more observational facts of AXPs/SGRs.展开更多
针对多用户多目标通感服务的全空间覆盖问题,研究了有源同时传输和反射可重构智能表面(Simultaneously Transmitting and Reflecting Reconfigurable Intelligent Surface,STAR-RIS)辅助的通信感知一体化(Integrated Sensing and Commun...针对多用户多目标通感服务的全空间覆盖问题,研究了有源同时传输和反射可重构智能表面(Simultaneously Transmitting and Reflecting Reconfigurable Intelligent Surface,STAR-RIS)辅助的通信感知一体化(Integrated Sensing and Communication,ISAC)系统。不同于已有研究工作,本方案建模优化了有源STAR-RIS的幅度参数。在满足各通信用户的信干噪比、各感知目标的照射波束增益以及有源STAR-RIS的硬件约束等条件下,以系统总功率最小化为准则,建模ISAC基站发射波束赋形矢量和有源STAR-RIS相移/幅度等关键参数的联合优化设计问题。为快速解决该复杂的非凸联合优化设计问题,首先将其分解为ISAC基站发射波束赋形设计、有源STAR-RIS元件相移参数设计和幅度参数优化这3个子问题,然后采取块坐标下降策略,迭代求解获取最优解。仿真结果显示,相比于已有方案,本方案提出的联合优化设计算法有效降低了系统总功率30%,能取得复杂度和通信感知性能的良好折中。展开更多
The simultaneous transmitting and reflecting reconfigurable intelligent surface(STAR-RIS)can independently adjust surface’s reflection and transmission coefficients so as to enhance space coverage.For a multiple-inpu...The simultaneous transmitting and reflecting reconfigurable intelligent surface(STAR-RIS)can independently adjust surface’s reflection and transmission coefficients so as to enhance space coverage.For a multiple-input multiple-output(MIMO)communication system with a STAR-RIS,a base station(BS),an eavesdropper,and multiple users,the system security rate is studied.A joint design of the power allocation at the transmitter and phase shift matrices for reflection and transmission at the STAR-RIS is conducted,in order to maximize the worst achievable security data rate(ASDR).Since the problem is nonconvex and hence challenging,a particle swarm optimization(PSO)based algorithm is developed to tackle the problem.Both the cases of continuous and discrete phase shift matrices at the STAR-RIS are considered.Simulation results demonstrate the effectiveness of the proposed algorithm and shows the benefits of using STAR-RIS in MIMO mutliuser systems.展开更多
基金supported by the National Natural Science Foundation of China(12273008,12025303,12403046)the National SKA Program of China(2022SKA0130104)+3 种基金the Natural Science and Technology Foundation of Guizhou Province(QiankehejichuMS[2025]266,[2023]024,ZK[2022]304)the Foundation of Guizhou Provincial Education Department(KY(2020)003)the Academic New Seedling Fund Project of Guizhou Normal University([2022]B18)the Major Science and Technology Program of Xinjiang Uygur Autonomous Region(2022A03013-4).
文摘The emission of anomalous X-ray pulsars(AXPs)and soft gamma-ray repeaters(SGRs)is believed to be powered by the dissipation of their strong magnetic fields,which coined the name“magnetar”.By combining timing and energy observational results,the magnetar model can be easily appreciated.From a timing perspective,the magnetic field strengths of AXPs and SGRs,which are calculated under the assumption of dipole radiation,are extremely strong.From an energy perspective,the X-ray/soft gamma-ray luminosities of AXPs and SGRs are larger than their rotational energy loss rates(i.e.,L_(x>E_(rot)).It is thus reasonable to assume that the high-energy radiation comes from magnetic energy decay,and the magnetar model has been extensively discussed(or accepted).However,we argue that:(ⅰ)Calculating magnetic fields by assuming that rotational energy loss is dominated by dipole radiation(i.e.,E_(rot)■E_(μ))may be controversial,and we suggest that the energies carried by outflowing particles should also be considered.(ⅱ)The fact that X-ray luminosity is greater than the rotational energy loss rate does not necessarily mean that the emission energy comes from the magnetic field decaying,which requires further observational testing.Furthermore,some observational facts conflict with the“magnetar”model,such as observations of anti-magnetars,high magnetic field pulsars,and radio and X-ray observations of AXPs/SGRs.Therefore,we propose a crusted strange star model as an alternative,which can explain many more observational facts of AXPs/SGRs.
文摘针对多用户多目标通感服务的全空间覆盖问题,研究了有源同时传输和反射可重构智能表面(Simultaneously Transmitting and Reflecting Reconfigurable Intelligent Surface,STAR-RIS)辅助的通信感知一体化(Integrated Sensing and Communication,ISAC)系统。不同于已有研究工作,本方案建模优化了有源STAR-RIS的幅度参数。在满足各通信用户的信干噪比、各感知目标的照射波束增益以及有源STAR-RIS的硬件约束等条件下,以系统总功率最小化为准则,建模ISAC基站发射波束赋形矢量和有源STAR-RIS相移/幅度等关键参数的联合优化设计问题。为快速解决该复杂的非凸联合优化设计问题,首先将其分解为ISAC基站发射波束赋形设计、有源STAR-RIS元件相移参数设计和幅度参数优化这3个子问题,然后采取块坐标下降策略,迭代求解获取最优解。仿真结果显示,相比于已有方案,本方案提出的联合优化设计算法有效降低了系统总功率30%,能取得复杂度和通信感知性能的良好折中。
文摘The simultaneous transmitting and reflecting reconfigurable intelligent surface(STAR-RIS)can independently adjust surface’s reflection and transmission coefficients so as to enhance space coverage.For a multiple-input multiple-output(MIMO)communication system with a STAR-RIS,a base station(BS),an eavesdropper,and multiple users,the system security rate is studied.A joint design of the power allocation at the transmitter and phase shift matrices for reflection and transmission at the STAR-RIS is conducted,in order to maximize the worst achievable security data rate(ASDR).Since the problem is nonconvex and hence challenging,a particle swarm optimization(PSO)based algorithm is developed to tackle the problem.Both the cases of continuous and discrete phase shift matrices at the STAR-RIS are considered.Simulation results demonstrate the effectiveness of the proposed algorithm and shows the benefits of using STAR-RIS in MIMO mutliuser systems.
