随着大量新能源场站接入交直流混联电网,系统的静态电压稳定裕度(static voltage stability margin,SVSM)水平具有很大的不确定性,需要研究考虑新能源场站高阶不确定性的交直流混联电网SVSM计算方法。针对此问题,首先建立了交直流混联电...随着大量新能源场站接入交直流混联电网,系统的静态电压稳定裕度(static voltage stability margin,SVSM)水平具有很大的不确定性,需要研究考虑新能源场站高阶不确定性的交直流混联电网SVSM计算方法。针对此问题,首先建立了交直流混联电网SVSM计算模型,模型中考虑了直流换流站控制方式随负荷增长的切换;采用概率盒模型描述风速与光照强度的随机波动,提出了改进区间半不变量法以获得更准确的SVSM概率盒,该方法通过K-means++聚类算法将随机变量样本划分为多个波动范围较小的样本集,以降低半不变量的线性化计算带来的误差;并结合Gram-Charlier级数展开和概率加权和计算得到考虑新能源场站高阶不确定性的系统SVSM概率盒。通过对修改的IEEE-39节点交直流系统和南方电网两个算例的分析,并与区间半不变量法和双层蒙特卡洛法比较,验证了所提出方法获得的SVSM概率盒具有较高的计算精度和效率。展开更多
In this paper we develop an elasto-dynamic model of the human arm that includes effects of neuro-muscular control upon elastic deformation in the limb.The elasto-dynamic model of the arm is based on hybrid parameter m...In this paper we develop an elasto-dynamic model of the human arm that includes effects of neuro-muscular control upon elastic deformation in the limb.The elasto-dynamic model of the arm is based on hybrid parameter multiple body system variational projection principles presented in the companion paper.Though the technique is suitable for detailed bone and joint modeling,we present simulations for simplified geometry of the bones,discretized as Rayleigh beams with elongation,while allowing for large deflections.Motion of the upper extremity is simulated by incorporating muscle forces derived from a Hill-type model of musculotendon dynamics.The effects of muscle force are modeled in two ways.In one approach,an effective joint torque is calculated by multiplying the muscle force by a joint moment ann.A second approach models the muscle as acting along a straight line between the origin and insertion sites of the tendon.Simple arm motion is simulated by utilizing neural feedback and feedforward control.Simulations illustrate the combined effects of neural control strategies, models of muscle force inclusion,and elastic assumptions on joint trajectories and stress and strain development in the bone and tendon.展开更多
In this paper we develop an elasto-dynamic model of the human arm for use in neuro-muscular control and dynamic interaction studies.The motivation for this work is to present a case for developing and using non-quasis...In this paper we develop an elasto-dynamic model of the human arm for use in neuro-muscular control and dynamic interaction studies.The motivation for this work is to present a case for developing and using non-quasistatic models of human musculo-skeletal biomechanics.The model is based on hybrid parameter multiple body system(HPMBS)variational projection principles.In this paper,we present an overview of the HPMBS variational principle applied to the full elasto-dynamic model of the arm.The generality of the model allows one to incorporate muscle effects as either loads transmitted through the tendon at points of origin and insertion or as an effective torque at a joint.Though the technique is suitable for detailed bone and joint modeling,we present in this initial effort only simple geometry with the bones discretized as Rayleigh beams with elongation, while allowing for large deflections.Simulations demonstrate the viability of the mcthod for use in the companion paper and in future studies.展开更多
In this paper,the stabilization of a continuous time-delayed system is considered.To control the bifurcation and chaos in a time-delayed system,a parameter perturbation control and a hybrid control are proposed.Then,t...In this paper,the stabilization of a continuous time-delayed system is considered.To control the bifurcation and chaos in a time-delayed system,a parameter perturbation control and a hybrid control are proposed.Then,to ensure the asymptotic stability of the system in the presence of unexpected system parameter changes,the adaptive control idea is introduced,i.e.,the perturbation control parameter and the hybrid control parameter are automatically tuned according to the adaptation laws,respectively.The adaptation algorithms are constructed based on the Lyapunov-Krasovskii stability theorem.The adaptive parameter perturbation control and the adaptive hybrid control methods improve the corresponding constant control methods.They have the advantages of increased stability,adaptability to the changes of the system parameters,control cost saving,and simplicity.Numerical simulations for a well-known chaotic time-delayed system are performed to demonstrate the feasibility and superiority of the proposed control methods.A comparison of the two adaptive control methods is also made in an experimental study.展开更多
Reflectance model is a basic concept in computer vision. Some existing models combining the classical diffuse reflectance model and those for surfaces containing specular components can approximately describe real ref...Reflectance model is a basic concept in computer vision. Some existing models combining the classical diffuse reflectance model and those for surfaces containing specular components can approximately describe real reflectance. But the ratio of diffuse and specular reflection decided manually has no clear meaning. We propose a new polynomial hybrid reflectance model. The reflectance map equation with a known shape （for example cylinder） as a sample is used to estimate parameters of the proposed reflectance model by least square regression algorithm. Then the reflectance parameters for surfaces of the same class of materials can be determined. Experiments are performed for a metal surface. The synthesis images produced by the proposed method and existing ones are compared with the real acquired image, and the results show that the proposed reflectance model is suitable for describing real reflectance.展开更多
Automatic scaling ionogram can get the parameters of ionogram which are vital to ionosphere detecting. In this paper, a new method is proposed to scale F2 layer trace automatically from oblique ionogram based on morph...Automatic scaling ionogram can get the parameters of ionogram which are vital to ionosphere detecting. In this paper, a new method is proposed to scale F2 layer trace automatically from oblique ionogram based on morphological operator and inversion technique. This method is verified through the comparison of actual detecting data with statistical analysis. The results show that the proposed automatic scaling method has high acceptable rate and is suitable for scaling oblique ionogram with different high angle wave states. It is fast and precise to fit O-mode echoes in F2 layer without the influence from F1 layer. This method could be applied in real-time ionospheric oblique sounding research with high reliability and versatility.展开更多
Polymerizations with multiple mechanisms performed simultaneously are promising but very challenging. As the key limitation,the complicated mutual influence between different mechanisms can be hardly defined and measu...Polymerizations with multiple mechanisms performed simultaneously are promising but very challenging. As the key limitation,the complicated mutual influence between different mechanisms can be hardly defined and measured. Herein we establish a universal framework for the assessment of mutual influence between different mechanisms using binary polymerization for demonstration. The kinetics and thermodynamics of polymerization with two mechanisms are compared with the corresponding homopolymerization and the difference is expressed by a hybrid function. The hybrid function is composed of a hybrid parameter that describes the extent of mutual influence and a function that describes necessary conditions for mutual influence to occur. The extent of mutual influence can be calculated using kinetic and thermodynamic data without details of reaction mechanisms, for the first time providing a straightforward method to assess the mutual influence between different polymerization mechanisms.We envision that the method has potential in more complex systems with multiple mechanisms/monomers with mutual influence.展开更多
文摘随着大量新能源场站接入交直流混联电网,系统的静态电压稳定裕度(static voltage stability margin,SVSM)水平具有很大的不确定性,需要研究考虑新能源场站高阶不确定性的交直流混联电网SVSM计算方法。针对此问题,首先建立了交直流混联电网SVSM计算模型,模型中考虑了直流换流站控制方式随负荷增长的切换;采用概率盒模型描述风速与光照强度的随机波动,提出了改进区间半不变量法以获得更准确的SVSM概率盒,该方法通过K-means++聚类算法将随机变量样本划分为多个波动范围较小的样本集,以降低半不变量的线性化计算带来的误差;并结合Gram-Charlier级数展开和概率加权和计算得到考虑新能源场站高阶不确定性的系统SVSM概率盒。通过对修改的IEEE-39节点交直流系统和南方电网两个算例的分析,并与区间半不变量法和双层蒙特卡洛法比较,验证了所提出方法获得的SVSM概率盒具有较高的计算精度和效率。
文摘In this paper we develop an elasto-dynamic model of the human arm that includes effects of neuro-muscular control upon elastic deformation in the limb.The elasto-dynamic model of the arm is based on hybrid parameter multiple body system variational projection principles presented in the companion paper.Though the technique is suitable for detailed bone and joint modeling,we present simulations for simplified geometry of the bones,discretized as Rayleigh beams with elongation,while allowing for large deflections.Motion of the upper extremity is simulated by incorporating muscle forces derived from a Hill-type model of musculotendon dynamics.The effects of muscle force are modeled in two ways.In one approach,an effective joint torque is calculated by multiplying the muscle force by a joint moment ann.A second approach models the muscle as acting along a straight line between the origin and insertion sites of the tendon.Simple arm motion is simulated by utilizing neural feedback and feedforward control.Simulations illustrate the combined effects of neural control strategies, models of muscle force inclusion,and elastic assumptions on joint trajectories and stress and strain development in the bone and tendon.
文摘In this paper we develop an elasto-dynamic model of the human arm for use in neuro-muscular control and dynamic interaction studies.The motivation for this work is to present a case for developing and using non-quasistatic models of human musculo-skeletal biomechanics.The model is based on hybrid parameter multiple body system(HPMBS)variational projection principles.In this paper,we present an overview of the HPMBS variational principle applied to the full elasto-dynamic model of the arm.The generality of the model allows one to incorporate muscle effects as either loads transmitted through the tendon at points of origin and insertion or as an effective torque at a joint.Though the technique is suitable for detailed bone and joint modeling,we present in this initial effort only simple geometry with the bones discretized as Rayleigh beams with elongation, while allowing for large deflections.Simulations demonstrate the viability of the mcthod for use in the companion paper and in future studies.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10772043)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20090042110003)the Science Research Project of Education Department of Liaoning Province,China (Grant No. L2012208)
文摘In this paper,the stabilization of a continuous time-delayed system is considered.To control the bifurcation and chaos in a time-delayed system,a parameter perturbation control and a hybrid control are proposed.Then,to ensure the asymptotic stability of the system in the presence of unexpected system parameter changes,the adaptive control idea is introduced,i.e.,the perturbation control parameter and the hybrid control parameter are automatically tuned according to the adaptation laws,respectively.The adaptation algorithms are constructed based on the Lyapunov-Krasovskii stability theorem.The adaptive parameter perturbation control and the adaptive hybrid control methods improve the corresponding constant control methods.They have the advantages of increased stability,adaptability to the changes of the system parameters,control cost saving,and simplicity.Numerical simulations for a well-known chaotic time-delayed system are performed to demonstrate the feasibility and superiority of the proposed control methods.A comparison of the two adaptive control methods is also made in an experimental study.
基金This work was supported by the National Natural Sci-ence Foundation of China under Grant No.60502021.
文摘Reflectance model is a basic concept in computer vision. Some existing models combining the classical diffuse reflectance model and those for surfaces containing specular components can approximately describe real reflectance. But the ratio of diffuse and specular reflection decided manually has no clear meaning. We propose a new polynomial hybrid reflectance model. The reflectance map equation with a known shape （for example cylinder） as a sample is used to estimate parameters of the proposed reflectance model by least square regression algorithm. Then the reflectance parameters for surfaces of the same class of materials can be determined. Experiments are performed for a metal surface. The synthesis images produced by the proposed method and existing ones are compared with the real acquired image, and the results show that the proposed reflectance model is suitable for describing real reflectance.
基金Supported by the National Natural Science Foundation of China(59975035,41006058)the Fundamental Research Funds for the Central Universities(2014212020205)
文摘Automatic scaling ionogram can get the parameters of ionogram which are vital to ionosphere detecting. In this paper, a new method is proposed to scale F2 layer trace automatically from oblique ionogram based on morphological operator and inversion technique. This method is verified through the comparison of actual detecting data with statistical analysis. The results show that the proposed automatic scaling method has high acceptable rate and is suitable for scaling oblique ionogram with different high angle wave states. It is fast and precise to fit O-mode echoes in F2 layer without the influence from F1 layer. This method could be applied in real-time ionospheric oblique sounding research with high reliability and versatility.
基金supported by the National Natural Science Foundation of China (51690151, 22001166)。
文摘Polymerizations with multiple mechanisms performed simultaneously are promising but very challenging. As the key limitation,the complicated mutual influence between different mechanisms can be hardly defined and measured. Herein we establish a universal framework for the assessment of mutual influence between different mechanisms using binary polymerization for demonstration. The kinetics and thermodynamics of polymerization with two mechanisms are compared with the corresponding homopolymerization and the difference is expressed by a hybrid function. The hybrid function is composed of a hybrid parameter that describes the extent of mutual influence and a function that describes necessary conditions for mutual influence to occur. The extent of mutual influence can be calculated using kinetic and thermodynamic data without details of reaction mechanisms, for the first time providing a straightforward method to assess the mutual influence between different polymerization mechanisms.We envision that the method has potential in more complex systems with multiple mechanisms/monomers with mutual influence.
