To design a propeller for ship power plant,the interaction between ship hull and propeller must be taken into account.The main concern is to apply the wake effect of ship stern on the propeller performance.In this pap...To design a propeller for ship power plant,the interaction between ship hull and propeller must be taken into account.The main concern is to apply the wake effect of ship stern on the propeller performance.In this paper,a coupled BEM(Boundary Element Method)/RANS(Renolds-Averaged Navier−Stokes)solver is used to simulate propeller behind the hull in the self-propulsion test.The motivation of this work is to develop a practical tool to design marine propulsion system without suffering long computational time.An unsteady boundary element method which is also known as panel method is chosen to estimate the propeller forces.Propeller wakes are treated using a time marching wake alignment method.Also,a RANS code coupled with VoF equation is developed to consider the ship motions and wake field effects in the problem.A coupling algorithm is developed to interchange ship wake field to the potential flow solver and propeller thrust to the RANS code.Based on the difference between hull resistance and the propeller thrust,a PI controller is developed to compute the propeller RPM in every time step.Verification of the solver is carried out using the towing tank test report of a 50 m oceanography research vessel.Wake factor and trust deduction coefficient are estimated numerically.Also,the wake rollup pattern of the propeller in open water is compared with the propeller in real wake field.展开更多
随着信息技术的迅猛发展和人们对高速、低时延网络需求的不断增长,5G网络正成为实现智能化社会的关键基础设施。5G网络的低时延业务对于实现实时数据传输、物联网、虚拟现实的应用具有重要意义。基于此,介绍5G网络低时延业务对网络架构...随着信息技术的迅猛发展和人们对高速、低时延网络需求的不断增长,5G网络正成为实现智能化社会的关键基础设施。5G网络的低时延业务对于实现实时数据传输、物联网、虚拟现实的应用具有重要意义。基于此,介绍5G网络低时延业务对网络架构的要求,分析无线接入网IP化(internet protocol radio access network, IP RAN)组网技术,并对IP RAN组网架构中的关键技术加以研究,以期为相关人员提供参考。展开更多
The Service-based Architecture(SBA) is one of the key innovations of 5G architecture that leverage modularized, self-contained and independent services to provide flexible and cloud-native 5G network. In this paper, S...The Service-based Architecture(SBA) is one of the key innovations of 5G architecture that leverage modularized, self-contained and independent services to provide flexible and cloud-native 5G network. In this paper, SBA for Space-Air-Ground Integrated Network(SAGIN) is investigated to enable the 5G integration deployment. This paper proposes a novel Holistic Service-based Architecture(H-SBA)for SAGIN of 5G-Advanced and beyond, i.e., 6G. The H-SBA introduces the concept of end-to-end servicebased architecture design. The "Network Function Service", introduced in 5G SBA, is extended from Control Plane to User Plane, from core network to access network. Based on H-SBA, the new generation of protocol design is proposed, which proposes to use IETF QUIC and SRv6 to substitute 5G HTTP/2.0 and GTP-U. Testing results show that new protocols can achieve low latency and high throughput, making them promising candidate for H-SBA.展开更多
To accommodate the diversified emerging use cases in 5G,radio access networks(RAN)is required to be more flexible,open,and versatile.It is evolving towards cloudification,intelligence and openness.By embedding computi...To accommodate the diversified emerging use cases in 5G,radio access networks(RAN)is required to be more flexible,open,and versatile.It is evolving towards cloudification,intelligence and openness.By embedding computing capabilities within RAN,it helps to transform RAN into a natural cost effective radio edge computing platform,offering great opportunity to further enhance RAN agility for diversified services and improve users’quality of experience(Qo E).In this article,a logical architecture enabling deep convergence of communication and computing in RAN is proposed based on O-RAN.The scenarios and potential benefits of sharing RAN computing resources are first analyzed.Then,the requirements,design principles and logical architecture are introduced.Involved key technologies are also discussed,including heterogeneous computing infrastructure,unified computing and communication task modeling,joint communication and computing orchestration and RAN computing data routing.Followed by that,a VR use case is studied to illustrate the superiority of the joint communication and computing optimization.Finally,challenges and future trends are highlighted to provide some insights on the potential future work for researchers in this field.展开更多
The transition from middle-income to high-income stage is fraught with risks of growth divergence. Economic transition is clouded by the following possibilities: (1)falling share of industrial seetor through indust...The transition from middle-income to high-income stage is fraught with risks of growth divergence. Economic transition is clouded by the following possibilities: (1)falling share of industrial seetor through industrial depression and weakening growth momentum caused by the large urbanization costs; (2) the subordination of service sector as a result of nearly irreversibly industrial professional, which falters the process of service sector transition and upgrading," (3) inefficient knowledge production allocation and human capital upgrade due to the absence of incentivized compensation of knowledge consumption. We suggest that a country should reshape its efficiency model by upgrading knowledge factor and human capital as the pre-requisite. Given the dilemmas of transition, China should take the faetorization trend of service sector and reshape efficiency model through institutional reform, ensuring that service sector will develop in tandem with industrial sector.展开更多
Requirements of software systems tend to change over time. The speed of this tendency depends on the application domain the software system under consideration belongs to. If we consider novel contexts such as pervasi...Requirements of software systems tend to change over time. The speed of this tendency depends on the application domain the software system under consideration belongs to. If we consider novel contexts such as pervasive systems and systems supporting dynamic B2B interaction, requirements change so fast that the research community is studying how to build systems that are able to self-adapt on the fly to some of these changes. When this happens, the system does not need to undergo through a new development cycle thus increasing its availability and, to a certain extent, its robustness. So far, the research in the area of self-adaptive systems has been focusing on the definition of the mechanisms for supporting self-adaptation. We argue that what is missing now is a structured and robust design process associated to these mechanisms. This design process should include a Requirement Engineering (RE) phase that somewhat differs from the traditional one. However, the identification of requirements for adaptation requires a good knowledge of the context in which the system will be executed. In this work, we consider the modeling of such context as part of the RE phase and we particularly focus on Service-Based Applications (SBAs). We argue that RE activities should be supported at run-time to handle context changes and to support adaptation for SBAs. We survey the state of the art for what concerns the elicitation, modeling, and analysis of requirements and will highlight some issues and challenges in order to support adaptation for SBAs.展开更多
文摘To design a propeller for ship power plant,the interaction between ship hull and propeller must be taken into account.The main concern is to apply the wake effect of ship stern on the propeller performance.In this paper,a coupled BEM(Boundary Element Method)/RANS(Renolds-Averaged Navier−Stokes)solver is used to simulate propeller behind the hull in the self-propulsion test.The motivation of this work is to develop a practical tool to design marine propulsion system without suffering long computational time.An unsteady boundary element method which is also known as panel method is chosen to estimate the propeller forces.Propeller wakes are treated using a time marching wake alignment method.Also,a RANS code coupled with VoF equation is developed to consider the ship motions and wake field effects in the problem.A coupling algorithm is developed to interchange ship wake field to the potential flow solver and propeller thrust to the RANS code.Based on the difference between hull resistance and the propeller thrust,a PI controller is developed to compute the propeller RPM in every time step.Verification of the solver is carried out using the towing tank test report of a 50 m oceanography research vessel.Wake factor and trust deduction coefficient are estimated numerically.Also,the wake rollup pattern of the propeller in open water is compared with the propeller in real wake field.
文摘随着信息技术的迅猛发展和人们对高速、低时延网络需求的不断增长,5G网络正成为实现智能化社会的关键基础设施。5G网络的低时延业务对于实现实时数据传输、物联网、虚拟现实的应用具有重要意义。基于此,介绍5G网络低时延业务对网络架构的要求,分析无线接入网IP化(internet protocol radio access network, IP RAN)组网技术,并对IP RAN组网架构中的关键技术加以研究,以期为相关人员提供参考。
基金funded by Tsinghua University-China Mobile Communications Group Co., Ltd. Joint Institute。
文摘The Service-based Architecture(SBA) is one of the key innovations of 5G architecture that leverage modularized, self-contained and independent services to provide flexible and cloud-native 5G network. In this paper, SBA for Space-Air-Ground Integrated Network(SAGIN) is investigated to enable the 5G integration deployment. This paper proposes a novel Holistic Service-based Architecture(H-SBA)for SAGIN of 5G-Advanced and beyond, i.e., 6G. The H-SBA introduces the concept of end-to-end servicebased architecture design. The "Network Function Service", introduced in 5G SBA, is extended from Control Plane to User Plane, from core network to access network. Based on H-SBA, the new generation of protocol design is proposed, which proposes to use IETF QUIC and SRv6 to substitute 5G HTTP/2.0 and GTP-U. Testing results show that new protocols can achieve low latency and high throughput, making them promising candidate for H-SBA.
基金jointly supported by the Beijing University of Posts and Telecommunications-China Mobile Research Institute Joint Innovation Centerthe National Key Research and Development Program of China under Grant 2021YFB2900200the National Natural Science Foundation of China under Grant 62201073 and 61925101。
文摘To accommodate the diversified emerging use cases in 5G,radio access networks(RAN)is required to be more flexible,open,and versatile.It is evolving towards cloudification,intelligence and openness.By embedding computing capabilities within RAN,it helps to transform RAN into a natural cost effective radio edge computing platform,offering great opportunity to further enhance RAN agility for diversified services and improve users’quality of experience(Qo E).In this article,a logical architecture enabling deep convergence of communication and computing in RAN is proposed based on O-RAN.The scenarios and potential benefits of sharing RAN computing resources are first analyzed.Then,the requirements,design principles and logical architecture are introduced.Involved key technologies are also discussed,including heterogeneous computing infrastructure,unified computing and communication task modeling,joint communication and computing orchestration and RAN computing data routing.Followed by that,a VR use case is studied to illustrate the superiority of the joint communication and computing optimization.Finally,challenges and future trends are highlighted to provide some insights on the potential future work for researchers in this field.
基金sponsored by major tendering projects of National Social Sciences Foundation "Study on Accelerating Economic Adjustment and Coordinated Development"(Grant No.12&ZD084) and "Study on Contribution of Consumption to Economic Growth under Shifting Demand Structure"(Grant No.15ZDC011)projects of National Social Sciences Foundation "Study on China's Structural Growth Deceleration,Transition Risks and Efficiency Improvement Path"(Grant No.14AJL006) and "Study on the Scale,Spatial Clustering and Management Model of Chinese Cities"(Grant No.15ZDC011)
文摘The transition from middle-income to high-income stage is fraught with risks of growth divergence. Economic transition is clouded by the following possibilities: (1)falling share of industrial seetor through industrial depression and weakening growth momentum caused by the large urbanization costs; (2) the subordination of service sector as a result of nearly irreversibly industrial professional, which falters the process of service sector transition and upgrading," (3) inefficient knowledge production allocation and human capital upgrade due to the absence of incentivized compensation of knowledge consumption. We suggest that a country should reshape its efficiency model by upgrading knowledge factor and human capital as the pre-requisite. Given the dilemmas of transition, China should take the faetorization trend of service sector and reshape efficiency model through institutional reform, ensuring that service sector will develop in tandem with industrial sector.
文摘Requirements of software systems tend to change over time. The speed of this tendency depends on the application domain the software system under consideration belongs to. If we consider novel contexts such as pervasive systems and systems supporting dynamic B2B interaction, requirements change so fast that the research community is studying how to build systems that are able to self-adapt on the fly to some of these changes. When this happens, the system does not need to undergo through a new development cycle thus increasing its availability and, to a certain extent, its robustness. So far, the research in the area of self-adaptive systems has been focusing on the definition of the mechanisms for supporting self-adaptation. We argue that what is missing now is a structured and robust design process associated to these mechanisms. This design process should include a Requirement Engineering (RE) phase that somewhat differs from the traditional one. However, the identification of requirements for adaptation requires a good knowledge of the context in which the system will be executed. In this work, we consider the modeling of such context as part of the RE phase and we particularly focus on Service-Based Applications (SBAs). We argue that RE activities should be supported at run-time to handle context changes and to support adaptation for SBAs. We survey the state of the art for what concerns the elicitation, modeling, and analysis of requirements and will highlight some issues and challenges in order to support adaptation for SBAs.