相较于常用的跟网型变流器,构网型变流器(gridforming voltage source converter,GFM-VSC)凭借其优异的主动支撑能力和弱电网适应能力,能够显著提高电力电子化的新型电力系统的稳定性,目前在系统中接入构网型变流器已成为主流的研究趋...相较于常用的跟网型变流器,构网型变流器(gridforming voltage source converter,GFM-VSC)凭借其优异的主动支撑能力和弱电网适应能力,能够显著提高电力电子化的新型电力系统的稳定性,目前在系统中接入构网型变流器已成为主流的研究趋势。为支撑构网型变流器的大规模接入,亟需对其开展稳定性分析研究。为此提出了一种基于支路能量的GFM-VSC并网系统暂态同步稳定性定量判别指标。首先,考虑GFM-VSC中各控制环节各参数对暂态能量的影响,基于构网型特性规律构建了GFM-VSC并网系统支路能量函数,分析系统故障后处于稳定和失稳2种工况下的支路能量分布特性,并据此构建了GFM-VSC并网系统暂态同步稳定性定量判别指标。最后,通过仿真分析验证了该稳定性判别指标的有效性。展开更多
Convolutional neural networks （CNNs） have been applied in state-of-the-art visual tracking tasks to represent the target. However, most existing algorithms treat visual tracking as an object-specific task. Therefore...Convolutional neural networks （CNNs） have been applied in state-of-the-art visual tracking tasks to represent the target. However, most existing algorithms treat visual tracking as an object-specific task. Therefore, the model needs to be retrained for different test video sequences. We propose a branch-activated multi-domain convolutional neural network （BAMDCNN）. In contrast to most existing trackers based on CNNs which require frequent online training, BAMDCNN only needs offine training and online fine-tuning. Specifically, BAMDCNN exploits category-specific features that are more robust against variations. To allow for learning category-specific information, we introduce a group algorithm and a branch activation method. Experimental results on challenging benchmark show that the proposed algorithm outperforms other state-of-the-art methods. What＇s more, compared with CNN based trackers, BAMDCNN increases tracking speed.展开更多
Roots play an important role in stabilizing and strengthening soil. This article aims to study the mechanical properties of the interface between soil and roots with branches, using the pullout test method in the labo...Roots play an important role in stabilizing and strengthening soil. This article aims to study the mechanical properties of the interface between soil and roots with branches, using the pullout test method in the laboratory. The mechanical properties of the soil-root with branches interface is determined through the pullout-force and root-slippage curve （F-S curve）. The results of investigating 24 Pinus tabulaeformis single roots and 55 P. tabulaeformis roots with branches demonstrated three kinds of pullout test failures： breakage failure on branching root, breakage failure on branching node, and pullout failure. The branch angle had a remarkable effect on the failure mode of the roots with branches： the maximum pullout force increased with the sum of the branch diameters and the branch angle. The peak slippage and the initial force had a positive correlation with the sum of the branch diameter. The sig- nificance test of correlation between branch angle and the initial force, however, showed they had no correlation. Branch angle and branch root diameter affect the anchorage properties between root system and soil. Therefore, it is important to investigate the anchorage mechanics of the roots with branches to understand the mechanism of root reinforcement and anchorage.展开更多
In this paper, a branch-and-bound method for solving multi-dimensional quadratic 0-1 knapsack problems was studied. The method was based on the Lagrangian relaxation and the surrogate constraint technique for finding ...In this paper, a branch-and-bound method for solving multi-dimensional quadratic 0-1 knapsack problems was studied. The method was based on the Lagrangian relaxation and the surrogate constraint technique for finding feasible solutions. The Lagrangian relaxations were solved with the maximum-flow algorithm and the Lagrangian bounds was determined with the outer approximation method. Computational results show the efficiency of the proposed method for multi-dimensional quadratic 0-1 knapsack problems.展开更多
In this paper, a new branch-and-bound algorithm based on the Lagrangian dual relaxation and continuous relaxation is proposed for discrete multi-factor portfolio selection model with roundlot restriction in financial ...In this paper, a new branch-and-bound algorithm based on the Lagrangian dual relaxation and continuous relaxation is proposed for discrete multi-factor portfolio selection model with roundlot restriction in financial optimization. This discrete portfolio model is of integer quadratic programming problems. The separable structure of the model is investigated by using Lagrangian relaxation and dual search. Computational results show that the algorithm is capable of solving real-world portfolio problems with data from US stock market and randomly generated test problems with up to 120 securities.展开更多
One of the basic parameters in forest management planning is detailed knowledge of growing stock,information collected by forest inventory.Sampling methods must be accurate,inexpensive,and be easy to implement in the ...One of the basic parameters in forest management planning is detailed knowledge of growing stock,information collected by forest inventory.Sampling methods must be accurate,inexpensive,and be easy to implement in the field.This study presents a new sampling method called branching transect for use in the Iranian Zagros forests and similar forests.Features of the new method include greater accuracy,easy implementation in nature,simplicity of statistical calculations,and low cost.In this method,transect is used,which includes some subtransects(side branches).The length of the main transect,side branches,number of trees measured in each side branch,and the number of sub-branches in this method are changeable based on homogeneity,heterogeneity,and density of a forest.In this study,based on the density and heterogeneity of the forest area studied,20-m transects with four and eight side branches were used.Sampling plots(Transects)in four inventory networks(100 m×100 m,100 m×150 m,150 m×150 m and 100 m×200 m)were implemented in the GIS environment.The results of this sampling method were compared to the results of total inventory(100%count)in terms of accuracy,precision(t-test),and inventory error percentage.Branching transect results were statistially similar to total inventory counts in all cases.The results show that this method of estimating density and canopy per hectare can be used in Zagros forests and similar forests.展开更多
The dendrite growth process was simulated with the phase field model coupling with the fluctuation.The effect of fluctuation intensity on the dendrite morphology and that of the thermal fluctuation together with the p...The dendrite growth process was simulated with the phase field model coupling with the fluctuation.The effect of fluctuation intensity on the dendrite morphology and that of the thermal fluctuation together with the phase field fluctuation on the forming of side branches were investigated.The results indicate that with the decrease of thermal fluctuation amplitude,the furcation of dendrite tip also decreases,transverse dendrites become stronger,longitudinal dendrites become degenerated,Doublon structure disappears,and a quite symmetrical dendrite structure appears finally.Thermal fluctuation can result in the unsteadiness of dendrites side branches,and it is also the main reason for forming side branches.The phase field fluctuation has a little contribution to the side branches,and it is usually ignored in calculation.When the thermal fluctuation amplitude(F_u) is appropriate,the thermal noise can result in the side branches,but cannot change the steady behavior of the dendrites tip.展开更多
This paper constructs a new kind of block based bivariate blending rational interpolation via symmetric branched continued fractions. The construction process may be outlined as follows. The first step is to divide th...This paper constructs a new kind of block based bivariate blending rational interpolation via symmetric branched continued fractions. The construction process may be outlined as follows. The first step is to divide the original set of support points into some subsets (blocks). Then construct each block by using symmetric branched continued fraction. Finally assemble these blocks by Newton’s method to shape the whole interpolation scheme. Our new method offers many flexible bivariate blending rational interpolation schemes which include the classical bivariate Newton’s polynomial interpolation and symmetric branched continued fraction interpolation as its special cases. The block based bivariate blending rational interpolation is in fact a kind of tradeoff between the purely linear interpolation and the purely nonlinear interpolation. Finally, numerical examples are given to show the effectiveness of the proposed method.展开更多
This paper proposes a hybrid decoupled power flow method for balanced power distribution systems with distributed generation sources. The method formulates the power flow equations in active power and reactive power d...This paper proposes a hybrid decoupled power flow method for balanced power distribution systems with distributed generation sources. The method formulates the power flow equations in active power and reactive power decoupled form with polar coordinates. Second-order terms are included in the active power mismatch iteration, and constant Jacobian and Hessian matrices are used. A hybrid direct and indirect solution technique is used to achieve efficiency and robustness of the algorithm. Active power correction is solved by means of a sparse lower triangular and upper triangular （LU） decomposition algorithm with partial pivoting, and the reactive power correction is solved by means of restarted generalized minimal residual algorithm with an incomplete LU pre-conditioner. Typical distribution generation models and distribution load models are included. The impact of zero-impedance branches is explicitly modeled through reconfiguring of the adjacent branches with impedances. Numerical examples on a sample distribution system with widespread photovoltaic installations are given to demonstrate the effectiveness of the proposed method.展开更多
文摘相较于常用的跟网型变流器,构网型变流器(gridforming voltage source converter,GFM-VSC)凭借其优异的主动支撑能力和弱电网适应能力,能够显著提高电力电子化的新型电力系统的稳定性,目前在系统中接入构网型变流器已成为主流的研究趋势。为支撑构网型变流器的大规模接入,亟需对其开展稳定性分析研究。为此提出了一种基于支路能量的GFM-VSC并网系统暂态同步稳定性定量判别指标。首先,考虑GFM-VSC中各控制环节各参数对暂态能量的影响,基于构网型特性规律构建了GFM-VSC并网系统支路能量函数,分析系统故障后处于稳定和失稳2种工况下的支路能量分布特性,并据此构建了GFM-VSC并网系统暂态同步稳定性定量判别指标。最后,通过仿真分析验证了该稳定性判别指标的有效性。
基金the Innovation Action Plan Foundation of Shanghai(No.16511101200)
文摘Convolutional neural networks （CNNs） have been applied in state-of-the-art visual tracking tasks to represent the target. However, most existing algorithms treat visual tracking as an object-specific task. Therefore, the model needs to be retrained for different test video sequences. We propose a branch-activated multi-domain convolutional neural network （BAMDCNN）. In contrast to most existing trackers based on CNNs which require frequent online training, BAMDCNN only needs offine training and online fine-tuning. Specifically, BAMDCNN exploits category-specific features that are more robust against variations. To allow for learning category-specific information, we introduce a group algorithm and a branch activation method. Experimental results on challenging benchmark show that the proposed algorithm outperforms other state-of-the-art methods. What＇s more, compared with CNN based trackers, BAMDCNN increases tracking speed.
基金financially supported by the Fundamental Research Funds for the Central Universities(No.YX2010-20)the National Natural Science Foundation of China(No.31570708,No.30901162)the Open Projects Foundation of Key Laboratory of Soil and Water Conservation&Desertification Combat(Beijing Forestry University),Ministry of Education of China(No.201002)
文摘Roots play an important role in stabilizing and strengthening soil. This article aims to study the mechanical properties of the interface between soil and roots with branches, using the pullout test method in the laboratory. The mechanical properties of the soil-root with branches interface is determined through the pullout-force and root-slippage curve （F-S curve）. The results of investigating 24 Pinus tabulaeformis single roots and 55 P. tabulaeformis roots with branches demonstrated three kinds of pullout test failures： breakage failure on branching root, breakage failure on branching node, and pullout failure. The branch angle had a remarkable effect on the failure mode of the roots with branches： the maximum pullout force increased with the sum of the branch diameters and the branch angle. The peak slippage and the initial force had a positive correlation with the sum of the branch diameter. The sig- nificance test of correlation between branch angle and the initial force, however, showed they had no correlation. Branch angle and branch root diameter affect the anchorage properties between root system and soil. Therefore, it is important to investigate the anchorage mechanics of the roots with branches to understand the mechanism of root reinforcement and anchorage.
基金Project supported by the National Natural Science Foundation of China （Grant No.10571116）
文摘In this paper, a branch-and-bound method for solving multi-dimensional quadratic 0-1 knapsack problems was studied. The method was based on the Lagrangian relaxation and the surrogate constraint technique for finding feasible solutions. The Lagrangian relaxations were solved with the maximum-flow algorithm and the Lagrangian bounds was determined with the outer approximation method. Computational results show the efficiency of the proposed method for multi-dimensional quadratic 0-1 knapsack problems.
基金Project supported by the National Natural Science Foundation of China （Grant Nos.70518001. 70671064）
文摘In this paper, a new branch-and-bound algorithm based on the Lagrangian dual relaxation and continuous relaxation is proposed for discrete multi-factor portfolio selection model with roundlot restriction in financial optimization. This discrete portfolio model is of integer quadratic programming problems. The separable structure of the model is investigated by using Lagrangian relaxation and dual search. Computational results show that the algorithm is capable of solving real-world portfolio problems with data from US stock market and randomly generated test problems with up to 120 securities.
文摘One of the basic parameters in forest management planning is detailed knowledge of growing stock,information collected by forest inventory.Sampling methods must be accurate,inexpensive,and be easy to implement in the field.This study presents a new sampling method called branching transect for use in the Iranian Zagros forests and similar forests.Features of the new method include greater accuracy,easy implementation in nature,simplicity of statistical calculations,and low cost.In this method,transect is used,which includes some subtransects(side branches).The length of the main transect,side branches,number of trees measured in each side branch,and the number of sub-branches in this method are changeable based on homogeneity,heterogeneity,and density of a forest.In this study,based on the density and heterogeneity of the forest area studied,20-m transects with four and eight side branches were used.Sampling plots(Transects)in four inventory networks(100 m×100 m,100 m×150 m,150 m×150 m and 100 m×200 m)were implemented in the GIS environment.The results of this sampling method were compared to the results of total inventory(100%count)in terms of accuracy,precision(t-test),and inventory error percentage.Branching transect results were statistially similar to total inventory counts in all cases.The results show that this method of estimating density and canopy per hectare can be used in Zagros forests and similar forests.
文摘The dendrite growth process was simulated with the phase field model coupling with the fluctuation.The effect of fluctuation intensity on the dendrite morphology and that of the thermal fluctuation together with the phase field fluctuation on the forming of side branches were investigated.The results indicate that with the decrease of thermal fluctuation amplitude,the furcation of dendrite tip also decreases,transverse dendrites become stronger,longitudinal dendrites become degenerated,Doublon structure disappears,and a quite symmetrical dendrite structure appears finally.Thermal fluctuation can result in the unsteadiness of dendrites side branches,and it is also the main reason for forming side branches.The phase field fluctuation has a little contribution to the side branches,and it is usually ignored in calculation.When the thermal fluctuation amplitude(F_u) is appropriate,the thermal noise can result in the side branches,but cannot change the steady behavior of the dendrites tip.
基金Project supported by the National Natural Science Foundation of China (No. 10171026, No. 60473114) the AnhuiProvincial Natural Science Foundation, China (No. 03046102)the Research Funds for Young InnovationGroup, Education Department of Anhui Province (No. 2005TD03).
文摘This paper constructs a new kind of block based bivariate blending rational interpolation via symmetric branched continued fractions. The construction process may be outlined as follows. The first step is to divide the original set of support points into some subsets (blocks). Then construct each block by using symmetric branched continued fraction. Finally assemble these blocks by Newton’s method to shape the whole interpolation scheme. Our new method offers many flexible bivariate blending rational interpolation schemes which include the classical bivariate Newton’s polynomial interpolation and symmetric branched continued fraction interpolation as its special cases. The block based bivariate blending rational interpolation is in fact a kind of tradeoff between the purely linear interpolation and the purely nonlinear interpolation. Finally, numerical examples are given to show the effectiveness of the proposed method.
文摘This paper proposes a hybrid decoupled power flow method for balanced power distribution systems with distributed generation sources. The method formulates the power flow equations in active power and reactive power decoupled form with polar coordinates. Second-order terms are included in the active power mismatch iteration, and constant Jacobian and Hessian matrices are used. A hybrid direct and indirect solution technique is used to achieve efficiency and robustness of the algorithm. Active power correction is solved by means of a sparse lower triangular and upper triangular （LU） decomposition algorithm with partial pivoting, and the reactive power correction is solved by means of restarted generalized minimal residual algorithm with an incomplete LU pre-conditioner. Typical distribution generation models and distribution load models are included. The impact of zero-impedance branches is explicitly modeled through reconfiguring of the adjacent branches with impedances. Numerical examples on a sample distribution system with widespread photovoltaic installations are given to demonstrate the effectiveness of the proposed method.
