Mesh reflector antennas are the mainstream of large space-borne antennas,and the stretching of the truss achieves their deployment.Currently,the truss is commonly designed to be a single degree of freedom(DOF)deployab...Mesh reflector antennas are the mainstream of large space-borne antennas,and the stretching of the truss achieves their deployment.Currently,the truss is commonly designed to be a single degree of freedom(DOF)deployable mechanism with synchronization constraints.However,each deployable unit’s drive distribution and resistance load are uneven,and the forced synchronization constraints lead to the flexible deformation of rods and difficulties in the deployment scheme design.This paper introduces an asynchronous deployment scheme with a multi-DOF closed-chain deployable truss.The DOF of the truss is calculated,and the kinematic and dynamic models are established,considering the truss’s and cable net’s real-time coupling.An integrated solving algorithm for implicit differential-algebraic equations is proposed to solve the dynamic models.A prototype of a six-unit antenna was fabricated,and the experiment was carried out.The dynamic performances in synchronous and asynchronous deployment schemes are analyzed,and the results show that the cable resistance and truss kinetic energy impact under the asynchronous deployment scheme are minor,and the antenna is more straightforward to deploy.The work provides a new asynchronous deployment scheme and a universal antenna modeling method for dynamic design and performance improvement.展开更多
Mesh reflector antennas are widely used in space tasks owing to their light weight,high surface accuracy,and large folding ratio.They are stowed during launch and then fully deployed in orbit to form a mesh reflector ...Mesh reflector antennas are widely used in space tasks owing to their light weight,high surface accuracy,and large folding ratio.They are stowed during launch and then fully deployed in orbit to form a mesh reflector that transmits signals.Smooth deployment is essential for duty services;therefore,accurate and efficient dynamic modeling and analysis of the deployment process are essential.One major challenge is depicting time-varying resistance of the cable network and capturing the cable-truss coupling behavior during the deployment process.This paper proposes a general dynamic analysis methodology for cable-truss coupling.Considering the topological diversity and geometric nonlinearity,the cable network's equilibrium equation is derived,and an explicit expression of the time-varying tension of the boundary cables,which provides the main resistance in truss deployment,is obtained.The deployment dynamic model is established,which considers the coupling effect between the soft cables and deployable truss.The effects of the antenna's driving modes and parameters on the dynamic deployment performance were investigated.A scaled prototype was manufactured,and the deployment experiment was conducted to verify the accuracy of the proposed modeling method.The proposed methodology is suitable for general cable antennas with arbitrary topologies and parameters,providing theoretical guidance for the dynamic performance evaluation of antenna driving schemes.展开更多
Currently,distributed routing protocols are constrained by offering a single path between any pair of nodes,thereby limiting the potential throughput and overall network performance.This approach not only restricts th...Currently,distributed routing protocols are constrained by offering a single path between any pair of nodes,thereby limiting the potential throughput and overall network performance.This approach not only restricts the flow of data but also makes the network susceptible to failures in case the primary path is disrupted.In contrast,routing protocols that leverage multiple paths within the network offer a more resilient and efficient solution.Multipath routing,as a fundamental concept,surpasses the limitations of traditional shortest path first protocols.It not only redirects traffic to unused resources,effectively mitigating network congestion,but also ensures load balancing across the network.This optimization significantly improves network utilization and boosts the overall performance,making it a widely recognized efficient method for enhancing network reliability.To further strengthen network resilience against failures,we introduce a routing scheme known as Multiple Nodes with at least Two Choices(MNTC).This innovative approach aims to significantly enhance network availability by providing each node with at least two routing choices.By doing so,it not only reduces the dependency on a single path but also creates redundant paths that can be utilized in case of failures,thereby enhancing the overall resilience of the network.To ensure the optimal placement of nodes,we propose three incremental deployment algorithms.These algorithms carefully select the most suitable set of nodes for deployment,taking into account various factors such as node connectivity,traffic patterns,and network topology.By deployingMNTCon a carefully chosen set of nodes,we can significantly enhance network reliability without the need for a complete overhaul of the existing infrastructure.We have conducted extensive evaluations of MNTC in diverse topological spaces,demonstrating its effectiveness in maintaining high network availability with minimal path stretch.The results are impressive,showing that even when implemented on just 60%of nodes,our incremental deployment method significantly boosts network availability.This underscores the potential of MNTC in enhancing network resilience and performance,making it a viable solution for modern networks facing increasing demands and complexities.The algorithms OSPF,TBFH,DC and LFC perform fast rerouting based on strict conditions,while MNTC is not restricted by these conditions.In five real network topologies,the average network availability ofMNTCis improved by 14.68%,6.28%,4.76%and 2.84%,respectively,compared with OSPF,TBFH,DC and LFC.展开更多
针对传统柑橘种植抗灾能力弱、生产成本高、管理方式粗放,导致果品品质不稳定、病虫害频发的问题,文章提出了包含智能气象监测、水肥灌溉控制、视频监控及虫情监测功能的物联网(Internet of Things,IoT)设备空间布设方案,明确了组网搭...针对传统柑橘种植抗灾能力弱、生产成本高、管理方式粗放,导致果品品质不稳定、病虫害频发的问题,文章提出了包含智能气象监测、水肥灌溉控制、视频监控及虫情监测功能的物联网(Internet of Things,IoT)设备空间布设方案,明确了组网搭建、控制中心建设及运维管理的技术路线。实践表明,该方案依托实时监测数据实现果园精准管理,有效提高了水肥利用效率,显著降低了人工成本,同时提升了果品质量与果园管理效率,为智慧果园建设提供了参考。展开更多
目的:探讨新型帐篷医院系统手术模块展开与撤收的标准化操作方案。方法:从队员分工、操作顺序、操作技巧、注意事项等方面总结出一套手术模块展开与撤收的标准化操作方案并进行实施。记录方案实施前后各5次展开与撤收的操作时间、操作...目的:探讨新型帐篷医院系统手术模块展开与撤收的标准化操作方案。方法:从队员分工、操作顺序、操作技巧、注意事项等方面总结出一套手术模块展开与撤收的标准化操作方案并进行实施。记录方案实施前后各5次展开与撤收的操作时间、操作失误次数、装备损坏次数,并记录方案实施后队员操作结束后的即刻心率、个人最大心率百分比、主观体力感觉等级(rating of perceived exercise,RPE)评分。采用SPSS 26.0软件对数据进行统计分析。结果:实施标准化操作方案后,手术模块的展开、撤收时间分别为(58.23±8.513)min、(48.92±7.129)min,短于方案实施前[(85.15±11.430)min、(65.36±9.369)min],差异有统计学意义(P<0.05);方案实施后的操作失误次数、装备损坏次数均低于实施前;操作结束后队员的即刻心率为43~157次/min,平均为151.1次/min,个人最大心率百分比为75%~87%,平均为81.1%,RPE评分为14~17分,平均为15.3分,均属于中等作业强度。结论:标准化操作方案可实现手术模块的快速、高质量展开与撤收,能够满足实战及训练考核的需要,可在装备该新型帐篷医院系统手术模块的卫勤机构中推广应用。展开更多
Due to the long operation cycle of maritime transportation and frequent fluctuations of the bunker fuel price, the refueling expenditure of a chartered ship at different time or ports of call make significant differen...Due to the long operation cycle of maritime transportation and frequent fluctuations of the bunker fuel price, the refueling expenditure of a chartered ship at different time or ports of call make significant difference. From the perspective of shipping company, an optimal set of refueling schemes for a ship fleet operating on different voyage charter routes is an important decision. To address this issue, this paper presents an approach to optimize the refueling scheme and the ship deployment simultaneously with considering the trend of fuel price fluctuations. Firstly, an ARMA model is applied to forecast a time serials of the fuel prices. Then a mixed-integer nonlinear programming model is proposed to maximize total operating profit of the shipping company. Finally, a case study on a charter company with three bulk carriers and three voyage charter routes is conducted. The results show that the optimal solution saves the cost of 437,900 USD compared with the traditional refueling scheme, and verify the rationality and validity of the model.展开更多
To fully exploit the performance benefits of relay station (RS), in the two-hop cellular networks covering hotspots, when the number of RSs is predetermined, both RS deployment and frequency reuse scheme are jointly...To fully exploit the performance benefits of relay station (RS), in the two-hop cellular networks covering hotspots, when the number of RSs is predetermined, both RS deployment and frequency reuse scheme are jointly optimized for the purpose of maximizing the system capacity based on the constraints of system demand of capacity and the maximum number of outage demand nodes (MNDN). Further, considering the overhead of increasing RSs, it is desired to use minimum number of RSs. The joint RS deployment and frequency reuse scheme (JRDFR) problem is formulated into a mixed integer nonlinear programming, which is non-deterministic polynomial-time hard in general. A heuristic approach based on genetic algorithm is proposed to tackle the JRDFR problem. The computational experiment of the heuristic approach is achieved and optimized RS deployment and frequency reuse scheme is obtained. Finally, we discuss the impacts of MNDN and the number of RSs on the system performance.展开更多
基金supported by the National Key R&D Program of China(Grant No.2023YFB3407103)the National Natural Science Foundation of China(Grant Nos.52175242 and 52175027)Young Elite Scientists Sponsorship Program by China Association for Science and Technology(Grant No.2022QNRC001).
摘要Mesh reflector antennas are the mainstream of large space-borne antennas,and the stretching of the truss achieves their deployment.Currently,the truss is commonly designed to be a single degree of freedom(DOF)deployable mechanism with synchronization constraints.However,each deployable unit’s drive distribution and resistance load are uneven,and the forced synchronization constraints lead to the flexible deformation of rods and difficulties in the deployment scheme design.This paper introduces an asynchronous deployment scheme with a multi-DOF closed-chain deployable truss.The DOF of the truss is calculated,and the kinematic and dynamic models are established,considering the truss’s and cable net’s real-time coupling.An integrated solving algorithm for implicit differential-algebraic equations is proposed to solve the dynamic models.A prototype of a six-unit antenna was fabricated,and the experiment was carried out.The dynamic performances in synchronous and asynchronous deployment schemes are analyzed,and the results show that the cable resistance and truss kinetic energy impact under the asynchronous deployment scheme are minor,and the antenna is more straightforward to deploy.The work provides a new asynchronous deployment scheme and a universal antenna modeling method for dynamic design and performance improvement.
基金Supported by National Key R&D Program of China (Grant No.2023YFB3407103)National Natural Science Foundation of China (Grant Nos.52175242,52175027)Young Elite Scientists Sponsorship Program by CAST (Grant No.2022QNRC001)。
摘要Mesh reflector antennas are widely used in space tasks owing to their light weight,high surface accuracy,and large folding ratio.They are stowed during launch and then fully deployed in orbit to form a mesh reflector that transmits signals.Smooth deployment is essential for duty services;therefore,accurate and efficient dynamic modeling and analysis of the deployment process are essential.One major challenge is depicting time-varying resistance of the cable network and capturing the cable-truss coupling behavior during the deployment process.This paper proposes a general dynamic analysis methodology for cable-truss coupling.Considering the topological diversity and geometric nonlinearity,the cable network's equilibrium equation is derived,and an explicit expression of the time-varying tension of the boundary cables,which provides the main resistance in truss deployment,is obtained.The deployment dynamic model is established,which considers the coupling effect between the soft cables and deployable truss.The effects of the antenna's driving modes and parameters on the dynamic deployment performance were investigated.A scaled prototype was manufactured,and the deployment experiment was conducted to verify the accuracy of the proposed modeling method.The proposed methodology is suitable for general cable antennas with arbitrary topologies and parameters,providing theoretical guidance for the dynamic performance evaluation of antenna driving schemes.
基金supported by Fundamental Research Program of Shanxi Province(No.20210302123444)the Research Project at the College Level of China Institute of Labor Relations(No.23XYJS018)+2 种基金the ICH Digitalization and Multi-Source Information Fusion Fujian Provincial University Engineering Research Center 2022 Open Fund Project(G3-KF2207)the China University Industry University Research Innovation Fund(No.2021FNA02009)the Key R&D Program(International Science and Technology Cooperation Project)of Shanxi Province China(No.201903D421003).
摘要Currently,distributed routing protocols are constrained by offering a single path between any pair of nodes,thereby limiting the potential throughput and overall network performance.This approach not only restricts the flow of data but also makes the network susceptible to failures in case the primary path is disrupted.In contrast,routing protocols that leverage multiple paths within the network offer a more resilient and efficient solution.Multipath routing,as a fundamental concept,surpasses the limitations of traditional shortest path first protocols.It not only redirects traffic to unused resources,effectively mitigating network congestion,but also ensures load balancing across the network.This optimization significantly improves network utilization and boosts the overall performance,making it a widely recognized efficient method for enhancing network reliability.To further strengthen network resilience against failures,we introduce a routing scheme known as Multiple Nodes with at least Two Choices(MNTC).This innovative approach aims to significantly enhance network availability by providing each node with at least two routing choices.By doing so,it not only reduces the dependency on a single path but also creates redundant paths that can be utilized in case of failures,thereby enhancing the overall resilience of the network.To ensure the optimal placement of nodes,we propose three incremental deployment algorithms.These algorithms carefully select the most suitable set of nodes for deployment,taking into account various factors such as node connectivity,traffic patterns,and network topology.By deployingMNTCon a carefully chosen set of nodes,we can significantly enhance network reliability without the need for a complete overhaul of the existing infrastructure.We have conducted extensive evaluations of MNTC in diverse topological spaces,demonstrating its effectiveness in maintaining high network availability with minimal path stretch.The results are impressive,showing that even when implemented on just 60%of nodes,our incremental deployment method significantly boosts network availability.This underscores the potential of MNTC in enhancing network resilience and performance,making it a viable solution for modern networks facing increasing demands and complexities.The algorithms OSPF,TBFH,DC and LFC perform fast rerouting based on strict conditions,while MNTC is not restricted by these conditions.In five real network topologies,the average network availability ofMNTCis improved by 14.68%,6.28%,4.76%and 2.84%,respectively,compared with OSPF,TBFH,DC and LFC.
摘要针对传统柑橘种植抗灾能力弱、生产成本高、管理方式粗放,导致果品品质不稳定、病虫害频发的问题,文章提出了包含智能气象监测、水肥灌溉控制、视频监控及虫情监测功能的物联网(Internet of Things,IoT)设备空间布设方案,明确了组网搭建、控制中心建设及运维管理的技术路线。实践表明,该方案依托实时监测数据实现果园精准管理,有效提高了水肥利用效率,显著降低了人工成本,同时提升了果品质量与果园管理效率,为智慧果园建设提供了参考。
摘要目的:探讨新型帐篷医院系统手术模块展开与撤收的标准化操作方案。方法:从队员分工、操作顺序、操作技巧、注意事项等方面总结出一套手术模块展开与撤收的标准化操作方案并进行实施。记录方案实施前后各5次展开与撤收的操作时间、操作失误次数、装备损坏次数,并记录方案实施后队员操作结束后的即刻心率、个人最大心率百分比、主观体力感觉等级(rating of perceived exercise,RPE)评分。采用SPSS 26.0软件对数据进行统计分析。结果:实施标准化操作方案后,手术模块的展开、撤收时间分别为(58.23±8.513)min、(48.92±7.129)min,短于方案实施前[(85.15±11.430)min、(65.36±9.369)min],差异有统计学意义(P<0.05);方案实施后的操作失误次数、装备损坏次数均低于实施前;操作结束后队员的即刻心率为43~157次/min,平均为151.1次/min,个人最大心率百分比为75%~87%,平均为81.1%,RPE评分为14~17分,平均为15.3分,均属于中等作业强度。结论:标准化操作方案可实现手术模块的快速、高质量展开与撤收,能够满足实战及训练考核的需要,可在装备该新型帐篷医院系统手术模块的卫勤机构中推广应用。
基金Supported by the National Natural Science Foundation of China(71303026)China Postdoctoral Science Foundation(2015M580128)+2 种基金Liaoning Natural Science Foundation(2015020074)Higher Education Development Fund(for Collaborative Innovation Center)of Liaoning(20110116102)Teaching Reform Fund of Dalian Maritime University(2014Y18)
摘要Due to the long operation cycle of maritime transportation and frequent fluctuations of the bunker fuel price, the refueling expenditure of a chartered ship at different time or ports of call make significant difference. From the perspective of shipping company, an optimal set of refueling schemes for a ship fleet operating on different voyage charter routes is an important decision. To address this issue, this paper presents an approach to optimize the refueling scheme and the ship deployment simultaneously with considering the trend of fuel price fluctuations. Firstly, an ARMA model is applied to forecast a time serials of the fuel prices. Then a mixed-integer nonlinear programming model is proposed to maximize total operating profit of the shipping company. Finally, a case study on a charter company with three bulk carriers and three voyage charter routes is conducted. The results show that the optimal solution saves the cost of 437,900 USD compared with the traditional refueling scheme, and verify the rationality and validity of the model.
摘要To fully exploit the performance benefits of relay station (RS), in the two-hop cellular networks covering hotspots, when the number of RSs is predetermined, both RS deployment and frequency reuse scheme are jointly optimized for the purpose of maximizing the system capacity based on the constraints of system demand of capacity and the maximum number of outage demand nodes (MNDN). Further, considering the overhead of increasing RSs, it is desired to use minimum number of RSs. The joint RS deployment and frequency reuse scheme (JRDFR) problem is formulated into a mixed integer nonlinear programming, which is non-deterministic polynomial-time hard in general. A heuristic approach based on genetic algorithm is proposed to tackle the JRDFR problem. The computational experiment of the heuristic approach is achieved and optimized RS deployment and frequency reuse scheme is obtained. Finally, we discuss the impacts of MNDN and the number of RSs on the system performance.