Three-Dimensional(3D)swirling flow structures,generated by a counter-rotating dualstage swirler in a confined chamber with a confinement ratio of 1.53,were experimentally investigated at Re=2.3×10^(5)using Tomogr...Three-Dimensional(3D)swirling flow structures,generated by a counter-rotating dualstage swirler in a confined chamber with a confinement ratio of 1.53,were experimentally investigated at Re=2.3×10^(5)using Tomographic Particle Image Velocimetry(Tomo-PIV)and planar Particle Image Velocimetry(PIV).Based on the analysis of the 3D time-averaged swirling flow structures and 3D Proper Orthogonal Decomposition(POD)of the Tomo-PIV data,typical coherent flow structures,including the Corner Recirculation Zone(CRZ),Central Recirculation Zone(CTRZ),and Lip Recirculation Zone(LRZ),were extracted.The counter-rotating dual-stage swirler with a Venturi flare generates the independence process of vortex breakdown from the main stage and pilot stage,leading to the formation of an LRZ and a smaller CTRZ near the nozzle outlet.The confinement squeezes the CRZ to the corner and causes a reverse rotation flow to limit the shape of the CTRZ.A large-scale flow structure caused by the main stage features an explosive breakup,flapping,and Precessing Vortex Core(PVC).The explosive breakup mode dominates the swirling flow structures owing to the expansion and construction of the main jet,whereas the flapping mode is related to the wake perturbation.Confinement limits the expansion of PVC and causes it to contract after the impacting area.展开更多
The tremendous performance gain of heterogeneous networks(Het Nets) is at the cost of complicated resource allocation. Considering information security, the resource allocation for Het Nets becomes much more challengi...The tremendous performance gain of heterogeneous networks(Het Nets) is at the cost of complicated resource allocation. Considering information security, the resource allocation for Het Nets becomes much more challenging and this is the focus of this paper. In this paper, the eavesdropper is hidden from the macro base stations. To relax the unpractical assumption on the channel state information on eavesdropper, a localization based algorithm is first given. Then a joint resource allocation algorithm is proposed in our work, which simultaneously considers physical layer security, cross-tier interference and joint optimization of power and subcarriers under fairness requirements. It is revealed in our work that the considered optimization problem can be efficiently solved relying on convex optimization theory and the Lagrangian dual decomposition method is exploited to solve the considered problem effectively. Moreover, in each iteration the closed-form optimal resource allocation solutions can be obtained based on the Karush-Kuhn-Tucker(KKT) conditions. Finally, the simulation results are given to show the performance advantages of the proposed algorithm.展开更多
The SDR-to-HDR translation technique can convert the abundant standard-dynamic-range (SDR) media resources to high-dynamic-range (HDR) ones, which can represent high-contrast scenes, providing more realistic visual ex...The SDR-to-HDR translation technique can convert the abundant standard-dynamic-range (SDR) media resources to high-dynamic-range (HDR) ones, which can represent high-contrast scenes, providing more realistic visual experiences. While recent vision Transformers have achieved promising performance in many low-level vision tasks, there are few works attempting to leverage Transformers for SDR-to-HDR translation. In this paper, we are among the first to investigate the performance of Transformers for SDR-to-HDR translation. We find that directly using the self-attention mechanism may involve artifacts in the results due to the inappropriate way to model long-range dependencies between the low-frequency and high-frequency components. Taking this into account, we advance the self-attention mechanism and present a dual frequency attention (DFA), which leverages the self-attention mechanism to separately encode the low-frequency structural information and high-frequency detail information. Based on the proposed DFA, we further design a multi-scale feature fusion network, named dual frequency Transformer (DFT), for efficient SDR-to-HDR translation. Extensive experiments on the HDRTV1K dataset demonstrate that our DFT can achieve better quantitative and qualitative performance than the recent state-of-the-art methods. The code of our DFT is made publicly available at https://github.com/CS-GangXu/DFT.展开更多
As the penetration ratio of wind power in active distribution networks continues to increase,the system exhibits some characteristics such as randomness and volatility.Fast and accurate short-term wind power predictio...As the penetration ratio of wind power in active distribution networks continues to increase,the system exhibits some characteristics such as randomness and volatility.Fast and accurate short-term wind power prediction is essential for algorithms like scheduling and optimization control.Based on the spatio-temporal features of Numerical Weather Prediction(NWP)data,it proposes the WVMD_DSN(Whale Optimization Algorithm,Variational Mode Decomposition,Dual Stream Network)model.The model first applies Pearson correlation coefficient(PCC)to choose some NWP features with strong correlation to wind power to form the feature set.Then,it decomposes the feature set using Variational Mode Decomposition(VMD)to eliminate the nonstationarity and obtains Intrinsic Mode Functions(IMFs).Here Whale Optimization Algorithm(WOA)is applied to optimise the key parameters of VMD,namely the number of mode components K and penalty factor a.Finally,incorporating attention mechanism(AM),Squeeze-Excitation Network(SENet),and Bidirectional Gated Recurrent Unit(BiGRU),it constructs the dual-stream network(DSN)for short-term wind power prediction.Comparative experiments demonstrate that the WVMD_DSN model outperforms existing baseline algorithms and exhibits good generalization performance.The relevant code is available at https://github.com/ruanyuyuan/Wind-power-forecast.git(accessed on 20 August 2024).展开更多
软件定义网络(Software Defined Network,SDN)和网络功能虚拟化(Network Function Virtualization,NFV)已经成为新一代网络体系结构的新范式。SDN和NFV可以有效地提高部署和管理服务功能链(Service Function Chains,SFCs)的灵活性。文...软件定义网络(Software Defined Network,SDN)和网络功能虚拟化(Network Function Virtualization,NFV)已经成为新一代网络体系结构的新范式。SDN和NFV可以有效地提高部署和管理服务功能链(Service Function Chains,SFCs)的灵活性。文中融合SDN和NFV,并应用到网络切片的资源优化中,为未来的5G三大业务场景实现定制服务的有效部署,提出了一种基于SDN和NFV的网络切片资源优化算法。首先针对5G uRLLC,eMBB,mMTC三大应用场景的不同业务需求,将底层的物理节点按照功能类型划分为三个虚拟子网的节点集合。然后根据不同应用场景的不同服务功能链的要求,分别对每一类的网络切片进行建模,形成混合整数线性规划的基于SDN和NFV的网络切片的数学模型,并提出了基于拉格朗日对偶分解的算法,将网络切片的数学模型转换为节点和链路的子问题,再对分解的子问题进行映射方案的求解。仿真结果表明,与以往算法相比,文中提出的算法在资源利用率、接受率、平均执行时间方面具有更好性能。展开更多
This paper studies the resource allocation for a multi-user two-way amplify-and-forward （AF） relay network over orthogonal frequency-division multiplexing （OFDM） technology, where all users communicate with their ...This paper studies the resource allocation for a multi-user two-way amplify-and-forward （AF） relay network over orthogonal frequency-division multiplexing （OFDM） technology, where all users communicate with their pre-assigned partners. Using convex optimization techniques, an optimal solution to minimize the total transmit power while satisfy each user-pair＇s data rate requirements is proposed. We divide the resource allocation problem into two subproblems： （1） power optimization within user-pair and relay in each subcarrier. （2） optimal subcarrier allocation and sum power assignment among N parallel OFDM subcarriers. Closed-form expressions of the power among user-pair and relay can be obtained in subproblem （1）, and so the proposed algorithm decreases the variable dimensionality of the objective function to reduce the complexity of this optimization problem. To solve it, a three-step suboptimal approach is proposed to assign the resources to user-pairs： Firstly, decompose each user-pair into two sub user-pairs which have one-way and two-way relaying transmission modes. Secondly, allocate the subcarriers to the new mode user-pairs and assign the transmit power to each carrier. Thirdly, distribute the assigned power to three nodes allocated in the subcarrier. Simulation results demonstrate the significant power is saved with the proposed solutions, as compared to a fixed subcarrier allocation.展开更多
基金supported by the National Natural Science Foundation of China(Nos.12232002,12072017,12002199,and 11721202)。
文摘Three-Dimensional(3D)swirling flow structures,generated by a counter-rotating dualstage swirler in a confined chamber with a confinement ratio of 1.53,were experimentally investigated at Re=2.3×10^(5)using Tomographic Particle Image Velocimetry(Tomo-PIV)and planar Particle Image Velocimetry(PIV).Based on the analysis of the 3D time-averaged swirling flow structures and 3D Proper Orthogonal Decomposition(POD)of the Tomo-PIV data,typical coherent flow structures,including the Corner Recirculation Zone(CRZ),Central Recirculation Zone(CTRZ),and Lip Recirculation Zone(LRZ),were extracted.The counter-rotating dual-stage swirler with a Venturi flare generates the independence process of vortex breakdown from the main stage and pilot stage,leading to the formation of an LRZ and a smaller CTRZ near the nozzle outlet.The confinement squeezes the CRZ to the corner and causes a reverse rotation flow to limit the shape of the CTRZ.A large-scale flow structure caused by the main stage features an explosive breakup,flapping,and Precessing Vortex Core(PVC).The explosive breakup mode dominates the swirling flow structures owing to the expansion and construction of the main jet,whereas the flapping mode is related to the wake perturbation.Confinement limits the expansion of PVC and causes it to contract after the impacting area.
基金supported by the National Natural Science Foundation of China under Grant No.61371075the 863 project SS2015AA011306
文摘The tremendous performance gain of heterogeneous networks(Het Nets) is at the cost of complicated resource allocation. Considering information security, the resource allocation for Het Nets becomes much more challenging and this is the focus of this paper. In this paper, the eavesdropper is hidden from the macro base stations. To relax the unpractical assumption on the channel state information on eavesdropper, a localization based algorithm is first given. Then a joint resource allocation algorithm is proposed in our work, which simultaneously considers physical layer security, cross-tier interference and joint optimization of power and subcarriers under fairness requirements. It is revealed in our work that the considered optimization problem can be efficiently solved relying on convex optimization theory and the Lagrangian dual decomposition method is exploited to solve the considered problem effectively. Moreover, in each iteration the closed-form optimal resource allocation solutions can be obtained based on the Karush-Kuhn-Tucker(KKT) conditions. Finally, the simulation results are given to show the performance advantages of the proposed algorithm.
基金supported by National Natural Science Foundation of China(Nos.61922046 and 62276145)the National Key Research and Development Program of China(No.2018AAA0100400)Fundamental Research Funds for Central Universities,China(No.63223049).
文摘The SDR-to-HDR translation technique can convert the abundant standard-dynamic-range (SDR) media resources to high-dynamic-range (HDR) ones, which can represent high-contrast scenes, providing more realistic visual experiences. While recent vision Transformers have achieved promising performance in many low-level vision tasks, there are few works attempting to leverage Transformers for SDR-to-HDR translation. In this paper, we are among the first to investigate the performance of Transformers for SDR-to-HDR translation. We find that directly using the self-attention mechanism may involve artifacts in the results due to the inappropriate way to model long-range dependencies between the low-frequency and high-frequency components. Taking this into account, we advance the self-attention mechanism and present a dual frequency attention (DFA), which leverages the self-attention mechanism to separately encode the low-frequency structural information and high-frequency detail information. Based on the proposed DFA, we further design a multi-scale feature fusion network, named dual frequency Transformer (DFT), for efficient SDR-to-HDR translation. Extensive experiments on the HDRTV1K dataset demonstrate that our DFT can achieve better quantitative and qualitative performance than the recent state-of-the-art methods. The code of our DFT is made publicly available at https://github.com/CS-GangXu/DFT.
基金the Science and Technology Project of State Grid Corporation of China under Grant 5400-202117142A-0-0-00the National Natural Science Foundation of China under Grant 62372242.
文摘As the penetration ratio of wind power in active distribution networks continues to increase,the system exhibits some characteristics such as randomness and volatility.Fast and accurate short-term wind power prediction is essential for algorithms like scheduling and optimization control.Based on the spatio-temporal features of Numerical Weather Prediction(NWP)data,it proposes the WVMD_DSN(Whale Optimization Algorithm,Variational Mode Decomposition,Dual Stream Network)model.The model first applies Pearson correlation coefficient(PCC)to choose some NWP features with strong correlation to wind power to form the feature set.Then,it decomposes the feature set using Variational Mode Decomposition(VMD)to eliminate the nonstationarity and obtains Intrinsic Mode Functions(IMFs).Here Whale Optimization Algorithm(WOA)is applied to optimise the key parameters of VMD,namely the number of mode components K and penalty factor a.Finally,incorporating attention mechanism(AM),Squeeze-Excitation Network(SENet),and Bidirectional Gated Recurrent Unit(BiGRU),it constructs the dual-stream network(DSN)for short-term wind power prediction.Comparative experiments demonstrate that the WVMD_DSN model outperforms existing baseline algorithms and exhibits good generalization performance.The relevant code is available at https://github.com/ruanyuyuan/Wind-power-forecast.git(accessed on 20 August 2024).
文摘软件定义网络(Software Defined Network,SDN)和网络功能虚拟化(Network Function Virtualization,NFV)已经成为新一代网络体系结构的新范式。SDN和NFV可以有效地提高部署和管理服务功能链(Service Function Chains,SFCs)的灵活性。文中融合SDN和NFV,并应用到网络切片的资源优化中,为未来的5G三大业务场景实现定制服务的有效部署,提出了一种基于SDN和NFV的网络切片资源优化算法。首先针对5G uRLLC,eMBB,mMTC三大应用场景的不同业务需求,将底层的物理节点按照功能类型划分为三个虚拟子网的节点集合。然后根据不同应用场景的不同服务功能链的要求,分别对每一类的网络切片进行建模,形成混合整数线性规划的基于SDN和NFV的网络切片的数学模型,并提出了基于拉格朗日对偶分解的算法,将网络切片的数学模型转换为节点和链路的子问题,再对分解的子问题进行映射方案的求解。仿真结果表明,与以往算法相比,文中提出的算法在资源利用率、接受率、平均执行时间方面具有更好性能。
基金supported by the National Natural Science Foundation of China (6035003,60572149)
文摘This paper studies the resource allocation for a multi-user two-way amplify-and-forward （AF） relay network over orthogonal frequency-division multiplexing （OFDM） technology, where all users communicate with their pre-assigned partners. Using convex optimization techniques, an optimal solution to minimize the total transmit power while satisfy each user-pair＇s data rate requirements is proposed. We divide the resource allocation problem into two subproblems： （1） power optimization within user-pair and relay in each subcarrier. （2） optimal subcarrier allocation and sum power assignment among N parallel OFDM subcarriers. Closed-form expressions of the power among user-pair and relay can be obtained in subproblem （1）, and so the proposed algorithm decreases the variable dimensionality of the objective function to reduce the complexity of this optimization problem. To solve it, a three-step suboptimal approach is proposed to assign the resources to user-pairs： Firstly, decompose each user-pair into two sub user-pairs which have one-way and two-way relaying transmission modes. Secondly, allocate the subcarriers to the new mode user-pairs and assign the transmit power to each carrier. Thirdly, distribute the assigned power to three nodes allocated in the subcarrier. Simulation results demonstrate the significant power is saved with the proposed solutions, as compared to a fixed subcarrier allocation.
