目的探讨以问题为导向的教学法(problerm-based learning,PBL)、情景教学法联合放射学信息系统(radiography information system,RIS)在超声医学本科实习教学中的应用价值。方法选取2020年6月—2022年6月在重庆医科大学附属大学城医院...目的探讨以问题为导向的教学法(problerm-based learning,PBL)、情景教学法联合放射学信息系统(radiography information system,RIS)在超声医学本科实习教学中的应用价值。方法选取2020年6月—2022年6月在重庆医科大学附属大学城医院超声科实习的医学影像专业本科实习生48名为研究对象,随机分为观察组24名学生,对照组24名学生,察组采用PBL、情景教学法联合RIS进行教学,对照组采用传统教学法进行教学,对2组出科考核成绩(理论、操作技能)、问卷调查进行比较。结果观察组的出科成绩理论为(88.24±2.18)分,操作为(84.47±3.49)分,均高于对照组的出科成绩理论(74.48±2.32)分,操作(71.33±3.24)分,差异有统计学意义(P<0.001);观察组满意度为95.83%,对照组满意度为79.17%,差异有统计学意义(P<0.05);观察组83.33%的学生认为PBL教学法+情景教学+RIS激发了学习兴趣,87.50%的学生认为训练了临床思维能力,91.67%的学生认为培养了团队协作能力,83.33%的学生认为提高了沟通能力,而对照组54.17%学生认为传统教学激发了学习兴趣,54.17%的学生认为训练了临床思维能力,45.83%的学生认为培养了团队协作能力,50.00%的学生认为提高了沟通能力,观察组的学习兴趣、学习主动性、团队协作意识、人文关怀意识、沟通能力、理论知识掌握、技能操作熟练程度、临床思维能力方面均优于对照组,差异有统计学意义(P<0.05)。结论PBL、情景学法联合RIS在超声实习教学中不仅有助于提高学生的专业素养,还有助于提高学生的综合素质,能提高教学效果,提升学生对教学的满意度。展开更多
Cell-free(CF)multiple-input multiple-output(MIMO)is a promising technique to enable the vision of ubiquitous wireless connectivity for next-generation network communications.Compared to traditional co-located massive ...Cell-free(CF)multiple-input multiple-output(MIMO)is a promising technique to enable the vision of ubiquitous wireless connectivity for next-generation network communications.Compared to traditional co-located massive MIMO,CF MIMO allows geographically distributed access points(APs)to serve all users on the same time-frequency resource with spatial multiplexing techniques,resulting in better performance in terms of both spectral efficiency and coverage enhancement.However,the performance gain is achieved at the expense of deploying more APs with high cost and power consumption.To address this issue,the recently proposed reconfigurable intelligent surface(RIS)technique stands out with its unique advantages of low cost,low energy consumption and programmability.In this paper,we provide an overview of RIS-assisted CF MIMO and its interaction with advanced optimization designs and novel applications.Particularly,recent studies on typical performance metrics such as energy efficiency(EE)and spectral efficiency(SE)are surveyed.Besides,the application of RIS-assisted CF MIMO techniques in various future communication systems is also envisioned.Additionally,we briefly discuss the technical challenges and open problems for this area to inspire research direction and fully exploit its potential in meeting the demands of future wireless communication systems.展开更多
Wireless avionics intra-communications(WAIC)is an emergent research topic,since it can improve fuel efficiency and enhance aircraft safety significantly.However,there are numerous baffles in an aircraft,e.g.,seats and...Wireless avionics intra-communications(WAIC)is an emergent research topic,since it can improve fuel efficiency and enhance aircraft safety significantly.However,there are numerous baffles in an aircraft,e.g.,seats and cabin bulkheads,resulting in serious blockage and even destroying wireless communications.Thus,this paper focuses on the reconfigurable intelligent surface(RIS)deployment issue of RIS-assisted WAIC systems,to solve the blockage problem caused by baffles.We first propose the mirror-symmetric imaging principle for mathematically analyzing electromagnetic(EM)wave propagation in a metal cuboid,which is a typical structure of WAIC systems.Based on the mirror-symmetric imaging principle,the mathematical channel model in a metal cuboid is deduced in detail.In addition,we develop an objective function of RIS's location and deduce the optimal RIS deployment location based on the geometric center optimization lemma.A two-dimensional gravity center search algorithm is then presented.Simulation results show that the designed RIS deployment can greatly increase the received power and efficiently solve the blockage problem in the aircraft.展开更多
Rate-splitting multiple access(RSMA)can cope with a wide range of propagation conditions in multigroup multicast communications through rate splitting optimization.To breakthrough the grouprate limited bottleneck,reco...Rate-splitting multiple access(RSMA)can cope with a wide range of propagation conditions in multigroup multicast communications through rate splitting optimization.To breakthrough the grouprate limited bottleneck,reconfigurable intelligent surface(RIS)technique can be introduced to assist wireless communications through enhancing the channel quality.In RIS-aided RSMA multigroup multicasting,how to provide fair and high-quality multiuser service under power and spectrum constraints is essential.In this paper,we propose a max-min fair RIS-aided rate-splitting multiple access(MMF-RISRSMA)scheme for multigroup multicast communications,where the rate fairness is obtained by maximizing the minimum group-rate.In doing so,we jointly optimize the beamformers,the rate splitting vector at the transmitter,as well as the phase shifts at RIS.To solve it,we divide the original optimization problem into two subproblems and alternately optimize the variables.The beamforming and rate splitting optimization subproblem is solved by using the successive convex approximation technique.The phase shift optimization subproblem is solved through the penalty function method to achieve a rank-one locally optimal solution.Simulations demonstrate that the proposed MMF-RIS-RSMA scheme can obtain significant performance gain in terms of the minimum group-rate.展开更多
Over-the-air computation(AirComp)based federated learning(FL)has been a promising technique for distilling artificial intelligence(AI)at the network edge.However,the performance of AirComp-based FL is decided by the d...Over-the-air computation(AirComp)based federated learning(FL)has been a promising technique for distilling artificial intelligence(AI)at the network edge.However,the performance of AirComp-based FL is decided by the device with the lowest channel gain due to the signal alignment property.More importantly,most existing work focuses on a single-cell scenario,where inter-cell interference is ignored.To overcome these shortages,a reconfigurable intelligent surface(RIS)-assisted AirComp-based FL system is proposed for multi-cell networks,where a RIS is used for enhancing the poor user signal caused by channel fading,especially for the device at the cell edge,and reducing inter-cell interference.The convergence of FL in the proposed system is first analyzed and the optimality gap for FL is derived.To minimize the optimality gap,we formulate a joint uplink and downlink optimization problem.The formulated problem is then divided into two separable nonconvex subproblems.Following the successive convex approximation(SCA)method,we first approximate the nonconvex term to a linear form,and then alternately optimize the beamforming vector and phase-shift matrix for each cell.Simulation results demonstrate the advantages of deploying a RIS in multi-cell networks and our proposed system significantly improves the performance of FL.展开更多
文摘目的探讨以问题为导向的教学法(problerm-based learning,PBL)、情景教学法联合放射学信息系统(radiography information system,RIS)在超声医学本科实习教学中的应用价值。方法选取2020年6月—2022年6月在重庆医科大学附属大学城医院超声科实习的医学影像专业本科实习生48名为研究对象,随机分为观察组24名学生,对照组24名学生,察组采用PBL、情景教学法联合RIS进行教学,对照组采用传统教学法进行教学,对2组出科考核成绩(理论、操作技能)、问卷调查进行比较。结果观察组的出科成绩理论为(88.24±2.18)分,操作为(84.47±3.49)分,均高于对照组的出科成绩理论(74.48±2.32)分,操作(71.33±3.24)分,差异有统计学意义(P<0.001);观察组满意度为95.83%,对照组满意度为79.17%,差异有统计学意义(P<0.05);观察组83.33%的学生认为PBL教学法+情景教学+RIS激发了学习兴趣,87.50%的学生认为训练了临床思维能力,91.67%的学生认为培养了团队协作能力,83.33%的学生认为提高了沟通能力,而对照组54.17%学生认为传统教学激发了学习兴趣,54.17%的学生认为训练了临床思维能力,45.83%的学生认为培养了团队协作能力,50.00%的学生认为提高了沟通能力,观察组的学习兴趣、学习主动性、团队协作意识、人文关怀意识、沟通能力、理论知识掌握、技能操作熟练程度、临床思维能力方面均优于对照组,差异有统计学意义(P<0.05)。结论PBL、情景学法联合RIS在超声实习教学中不仅有助于提高学生的专业素养,还有助于提高学生的综合素质,能提高教学效果,提升学生对教学的满意度。
基金supported in part by ZTE Industry-University-Institute Co⁃operation Funds.
文摘Cell-free(CF)multiple-input multiple-output(MIMO)is a promising technique to enable the vision of ubiquitous wireless connectivity for next-generation network communications.Compared to traditional co-located massive MIMO,CF MIMO allows geographically distributed access points(APs)to serve all users on the same time-frequency resource with spatial multiplexing techniques,resulting in better performance in terms of both spectral efficiency and coverage enhancement.However,the performance gain is achieved at the expense of deploying more APs with high cost and power consumption.To address this issue,the recently proposed reconfigurable intelligent surface(RIS)technique stands out with its unique advantages of low cost,low energy consumption and programmability.In this paper,we provide an overview of RIS-assisted CF MIMO and its interaction with advanced optimization designs and novel applications.Particularly,recent studies on typical performance metrics such as energy efficiency(EE)and spectral efficiency(SE)are surveyed.Besides,the application of RIS-assisted CF MIMO techniques in various future communication systems is also envisioned.Additionally,we briefly discuss the technical challenges and open problems for this area to inspire research direction and fully exploit its potential in meeting the demands of future wireless communication systems.
基金supported by the National Natural Science Foundation of China under Grand No.62071148 and No.62171151partly by the Natural Science Foundation of Heilongjiang Province of China under Grand No.YQ2019F009partly by the Fundamental Research Funds for Central Universities under Grand No.HIT.OCEF.2021012。
文摘Wireless avionics intra-communications(WAIC)is an emergent research topic,since it can improve fuel efficiency and enhance aircraft safety significantly.However,there are numerous baffles in an aircraft,e.g.,seats and cabin bulkheads,resulting in serious blockage and even destroying wireless communications.Thus,this paper focuses on the reconfigurable intelligent surface(RIS)deployment issue of RIS-assisted WAIC systems,to solve the blockage problem caused by baffles.We first propose the mirror-symmetric imaging principle for mathematically analyzing electromagnetic(EM)wave propagation in a metal cuboid,which is a typical structure of WAIC systems.Based on the mirror-symmetric imaging principle,the mathematical channel model in a metal cuboid is deduced in detail.In addition,we develop an objective function of RIS's location and deduce the optimal RIS deployment location based on the geometric center optimization lemma.A two-dimensional gravity center search algorithm is then presented.Simulation results show that the designed RIS deployment can greatly increase the received power and efficiently solve the blockage problem in the aircraft.
基金supported in part by the Project of International Cooperation and Exchanges NSFC under Grant No.61860206005in part by the National Natural Science Foundation of China under Grant No.62201329,No.62171262in part by Shandong Provincial Natural Science Foundation under Grant ZR2021YQ47。
文摘Rate-splitting multiple access(RSMA)can cope with a wide range of propagation conditions in multigroup multicast communications through rate splitting optimization.To breakthrough the grouprate limited bottleneck,reconfigurable intelligent surface(RIS)technique can be introduced to assist wireless communications through enhancing the channel quality.In RIS-aided RSMA multigroup multicasting,how to provide fair and high-quality multiuser service under power and spectrum constraints is essential.In this paper,we propose a max-min fair RIS-aided rate-splitting multiple access(MMF-RISRSMA)scheme for multigroup multicast communications,where the rate fairness is obtained by maximizing the minimum group-rate.In doing so,we jointly optimize the beamformers,the rate splitting vector at the transmitter,as well as the phase shifts at RIS.To solve it,we divide the original optimization problem into two subproblems and alternately optimize the variables.The beamforming and rate splitting optimization subproblem is solved by using the successive convex approximation technique.The phase shift optimization subproblem is solved through the penalty function method to achieve a rank-one locally optimal solution.Simulations demonstrate that the proposed MMF-RIS-RSMA scheme can obtain significant performance gain in terms of the minimum group-rate.
文摘Over-the-air computation(AirComp)based federated learning(FL)has been a promising technique for distilling artificial intelligence(AI)at the network edge.However,the performance of AirComp-based FL is decided by the device with the lowest channel gain due to the signal alignment property.More importantly,most existing work focuses on a single-cell scenario,where inter-cell interference is ignored.To overcome these shortages,a reconfigurable intelligent surface(RIS)-assisted AirComp-based FL system is proposed for multi-cell networks,where a RIS is used for enhancing the poor user signal caused by channel fading,especially for the device at the cell edge,and reducing inter-cell interference.The convergence of FL in the proposed system is first analyzed and the optimality gap for FL is derived.To minimize the optimality gap,we formulate a joint uplink and downlink optimization problem.The formulated problem is then divided into two separable nonconvex subproblems.Following the successive convex approximation(SCA)method,we first approximate the nonconvex term to a linear form,and then alternately optimize the beamforming vector and phase-shift matrix for each cell.Simulation results demonstrate the advantages of deploying a RIS in multi-cell networks and our proposed system significantly improves the performance of FL.
