The iterative Monte Carlo(MC)code EMC3-EIRENE is frequently used for plasma edge simulations in 3 D applications.So far,a quantitative evaluation of the numerical quality of the code results remains an open issue.In t...The iterative Monte Carlo(MC)code EMC3-EIRENE is frequently used for plasma edge simulations in 3 D applications.So far,a quantitative evaluation of the numerical quality of the code results remains an open issue.In this paper,we demonstrate a framework for the practical assessment of accuracy and convergence with EMC3-EIRENE.Moreover,we provide a first accuracy analysis with EMC3-EIRENE for a DIII-D divertor edge plasma case.First,we introduce post-processing averaging to efficiently reduce the variance of the statistical error.Then,we estimate the deterministic error contributions based on their theoretical reduction rates by comparing solutions with a different grid resolution,time step,or number of MC particles per iteration.Finally,using parameterized expressions for the error and the computational time,suitable numerical parameters are determined to achieve faster and/or more accurate results.We found that simulations can be more than twice as fast without losing accuracy by making use of post-processing averaging and choosing optimal parameters.In addition,we conclude that the discretization error is the dominant error contribution for the case selected in this paper,which demonstrates the importance of constructing an adequate mesh.展开更多
With the proliferation of the Internet of Things(IoT),various services are emerging with totally different features and requirements,which cannot be supported by the current fifth generation of mobile cellular network...With the proliferation of the Internet of Things(IoT),various services are emerging with totally different features and requirements,which cannot be supported by the current fifth generation of mobile cellular networks(5G).The future sixth generation of mobile cellular networks(6G)is expected to have the capability to support new and unknown services with changing requirements.Hence,in addition to enhancing its capability by 10–100 times compared with 5G,6G should also be intelligent and open to adapt to the ever-changing services in the IoT,which requires a convergence of Communication,Computing and Caching(3C).Based on the analysis of the requirements of new services for 6G,this paper identifies key enabling technologies for an intelligent and open 6G network,all featured with 3C convergence.These technologies cover fundamental and emerging topics,including 3C-based spectrum management,radio channel construction,delay-aware transmission,wireless distributed computing,and network self-evolution.From the detailed analysis of these 3C-based technologies presented in this paper,we can see that although they are promising to enable an intelligent and open 6G,more efforts are needed to realize the expected 6G network.展开更多
In meandering rivers, the flow pattern is highly complex, with specific characteristics at bends that are not observed along straight paths. A numerical model can be effectively used to predict such flow fields. Since...In meandering rivers, the flow pattern is highly complex, with specific characteristics at bends that are not observed along straight paths. A numerical model can be effectively used to predict such flow fields. Since river bends are not uniform-some are divergent and others convergent-in this study, after the SSIIM 3-D model was calibrated using the result of measurements along a uniform 180° bend with a width of 0.6 m, a similar but convergent 180v bend, 0.6 m to 0.45 m wide, was simulated using the SSI1M 3-D numerical model. Flow characteristics of the convergent 180° bend, including lengthwise and vertical velocity profiles, primary and secondary flows, lengthwise and widtbwise slopes of the water surface, and the helical flow strength, were compared with those of the uniform 180° bend. The verification results of the model show that the numerical model can effectively simulate the flow field in the uniform bend. In addition, this research indicates that, in a convergent channel, the maximum velocity path at a plane near the water surface crosses the channel＇s centerline at about a 30° to 40° cross-section, while in the uniform bend, this occurs at about the 50° cross-section. The varying range of the water surface elevation is wider in the convergent channel than in the uniform one, and the strength of the helical flow is generally greater in the uniform channel than in the convergent one. Also, unlike the uniform bend, the convergent bend exhibits no rotational cell against the main direction of secondary flow rotation at the 135° cross-section.展开更多
The action of the wind field and the influence of topography can cause divergence or convergence of surface current. The existence of the divergence-convergence effect is proved and the dynamical significance of the d...The action of the wind field and the influence of topography can cause divergence or convergence of surface current. The existence of the divergence-convergence effect is proved and the dynamical significance of the divergent or convergent state and its link with many marine phenomena are pointed out. Divergence fields of surface current in the Bohai Sea in winter and summer are obtained by numerical modelling describing the divergence-convergence character of seasonally wind-driven current. The relation between the effect and seasonal marine phenomena is discussed. Study on the divergence-convergence effect of surface current (DCESC)can be an indirect method for testing the calculated results.展开更多
全新世事件3是1997年由Bond等提出的、指的是发生在4.2 ka BP左右的冷事件。此后,冰心、海洋沉积物、湖泊沉积物、石笋和泥炭等各种地质载体被广泛用于全新世事件3的研究当中。此次事件在全球范围内普遍存在,在北半球中、低纬度大部分...全新世事件3是1997年由Bond等提出的、指的是发生在4.2 ka BP左右的冷事件。此后,冰心、海洋沉积物、湖泊沉积物、石笋和泥炭等各种地质载体被广泛用于全新世事件3的研究当中。此次事件在全球范围内普遍存在,在北半球中、低纬度大部分地区以冷干的气候条件为主,而在北半球高纬度地区和南半球部分地区则以冷湿的气候条件为主。同时,这次冷干或者冷湿的气候波动对于当时世界范围内的古文化变迁产生了重要的影响,是造成非洲尼罗河流域古埃及文明、两河流域美索不达米亚古阿卡德帝国、印度河流域哈拉帕文明以及中国新石器文化的衰落的主要原因。而全新世事件3的主要成因很可能是当时太阳活动减弱,一方面导致北大西洋表层浮冰增加,表层海水温度降低,减弱了温盐循环,使海陆温差减小,季风减弱;另一方面使热带幅合带南移,在北半球中、低纬度大部分地区形成干旱降温事件。展开更多
基金sponsored by Flanders Innovation and Entrepreneurship(IWT.141064)a travel grant(V4.128.18N)from Research Foundation—Flanders(FWO)+2 种基金supported by the Research Foundation Flanders(FWO)under project grant G078316Nfunded by the Research Foundation—Flanders(FWO)the Flemish Government—department EWI。
文摘The iterative Monte Carlo(MC)code EMC3-EIRENE is frequently used for plasma edge simulations in 3 D applications.So far,a quantitative evaluation of the numerical quality of the code results remains an open issue.In this paper,we demonstrate a framework for the practical assessment of accuracy and convergence with EMC3-EIRENE.Moreover,we provide a first accuracy analysis with EMC3-EIRENE for a DIII-D divertor edge plasma case.First,we introduce post-processing averaging to efficiently reduce the variance of the statistical error.Then,we estimate the deterministic error contributions based on their theoretical reduction rates by comparing solutions with a different grid resolution,time step,or number of MC particles per iteration.Finally,using parameterized expressions for the error and the computational time,suitable numerical parameters are determined to achieve faster and/or more accurate results.We found that simulations can be more than twice as fast without losing accuracy by making use of post-processing averaging and choosing optimal parameters.In addition,we conclude that the discretization error is the dominant error contribution for the case selected in this paper,which demonstrates the importance of constructing an adequate mesh.
基金This work is supported by the National Natural Science Youth Fund of China granted by No.61901452 and Innovative Project of ICT/CAS granted by No.20196110
文摘With the proliferation of the Internet of Things(IoT),various services are emerging with totally different features and requirements,which cannot be supported by the current fifth generation of mobile cellular networks(5G).The future sixth generation of mobile cellular networks(6G)is expected to have the capability to support new and unknown services with changing requirements.Hence,in addition to enhancing its capability by 10–100 times compared with 5G,6G should also be intelligent and open to adapt to the ever-changing services in the IoT,which requires a convergence of Communication,Computing and Caching(3C).Based on the analysis of the requirements of new services for 6G,this paper identifies key enabling technologies for an intelligent and open 6G network,all featured with 3C convergence.These technologies cover fundamental and emerging topics,including 3C-based spectrum management,radio channel construction,delay-aware transmission,wireless distributed computing,and network self-evolution.From the detailed analysis of these 3C-based technologies presented in this paper,we can see that although they are promising to enable an intelligent and open 6G,more efforts are needed to realize the expected 6G network.
文摘In meandering rivers, the flow pattern is highly complex, with specific characteristics at bends that are not observed along straight paths. A numerical model can be effectively used to predict such flow fields. Since river bends are not uniform-some are divergent and others convergent-in this study, after the SSIIM 3-D model was calibrated using the result of measurements along a uniform 180° bend with a width of 0.6 m, a similar but convergent 180v bend, 0.6 m to 0.45 m wide, was simulated using the SSI1M 3-D numerical model. Flow characteristics of the convergent 180° bend, including lengthwise and vertical velocity profiles, primary and secondary flows, lengthwise and widtbwise slopes of the water surface, and the helical flow strength, were compared with those of the uniform 180° bend. The verification results of the model show that the numerical model can effectively simulate the flow field in the uniform bend. In addition, this research indicates that, in a convergent channel, the maximum velocity path at a plane near the water surface crosses the channel＇s centerline at about a 30° to 40° cross-section, while in the uniform bend, this occurs at about the 50° cross-section. The varying range of the water surface elevation is wider in the convergent channel than in the uniform one, and the strength of the helical flow is generally greater in the uniform channel than in the convergent one. Also, unlike the uniform bend, the convergent bend exhibits no rotational cell against the main direction of secondary flow rotation at the 135° cross-section.
基金Contribution No.2110 from the Institute of Oceanology,Academia SinicaProject supported by the National Natural Science Foundation of China
文摘The action of the wind field and the influence of topography can cause divergence or convergence of surface current. The existence of the divergence-convergence effect is proved and the dynamical significance of the divergent or convergent state and its link with many marine phenomena are pointed out. Divergence fields of surface current in the Bohai Sea in winter and summer are obtained by numerical modelling describing the divergence-convergence character of seasonally wind-driven current. The relation between the effect and seasonal marine phenomena is discussed. Study on the divergence-convergence effect of surface current (DCESC)can be an indirect method for testing the calculated results.
文摘全新世事件3是1997年由Bond等提出的、指的是发生在4.2 ka BP左右的冷事件。此后,冰心、海洋沉积物、湖泊沉积物、石笋和泥炭等各种地质载体被广泛用于全新世事件3的研究当中。此次事件在全球范围内普遍存在,在北半球中、低纬度大部分地区以冷干的气候条件为主,而在北半球高纬度地区和南半球部分地区则以冷湿的气候条件为主。同时,这次冷干或者冷湿的气候波动对于当时世界范围内的古文化变迁产生了重要的影响,是造成非洲尼罗河流域古埃及文明、两河流域美索不达米亚古阿卡德帝国、印度河流域哈拉帕文明以及中国新石器文化的衰落的主要原因。而全新世事件3的主要成因很可能是当时太阳活动减弱,一方面导致北大西洋表层浮冰增加,表层海水温度降低,减弱了温盐循环,使海陆温差减小,季风减弱;另一方面使热带幅合带南移,在北半球中、低纬度大部分地区形成干旱降温事件。
