With the evolution of DC distribution networks from traditional radial topologies to more complex multi-branch structures,the number of measurement points supporting synchronous communication remains relatively limite...With the evolution of DC distribution networks from traditional radial topologies to more complex multi-branch structures,the number of measurement points supporting synchronous communication remains relatively limited.This poses challenges for conventional fault distance estimation methods,which are often tailored to simple topologies and are thus difficult to apply to large-scale,multi-node DC networks.To address this,a fault distance estimation method based on sparse measurement of high-frequency electrical quantities is proposed in this paper.First,a preliminary fault line identification model based on compressed sensing is constructed to effectively narrow the fault search range and improve localization efficiency.Then,leveraging the high-frequency impedance characteristics and the voltage-current relationship of electrical quantities,a fault distance estimation approach based on high-frequency measurements from both ends of a line is designed.This enables accurate distance estimation even when the measurement devices are not directly placed at both ends of the faulted line,overcoming the dependence on specific sensor placement inherent in traditional methods.Finally,to further enhance accuracy,an optimization model based on minimizing the high-frequency voltage error at the fault point is introduced to reduce estimation error.Simulation results demonstrate that the proposed method achieves a fault distance estimation error of less than 1%under normal conditions,and maintains good performance even under adverse scenarios.展开更多
In order to obtain related brain electrical components and neural bases of physiology assessment of icon elements in a digital human-computer interface the modified sample-delay matching task experimental paradigm is ...In order to obtain related brain electrical components and neural bases of physiology assessment of icon elements in a digital human-computer interface the modified sample-delay matching task experimental paradigm is used under different time pressures 4 000 and 2 000 ms and different icon quantities three five and ten icons on icon memory based on event-related potential ERP technology.Experimental results demonstrate that P300 has significant volatility changes and the maximum amplitude around the middle line of the parietal area PZ and P200 has obvious volatility changes around the middle line of the frontal and central area FCZ during icon cognition.P300 and P200 amplitudes increase as tasks become more difficult.Thus P300 latency is positively correlated with task difficulty. ERP research on the characteristics of icon memory will be an important reference standard in guiding user neurocognitive behavior and physiology assessment on interface usability.展开更多
The invariance of the ordinary differential equations under the infinitesimal transformations was used to study the Lie symmetries and conserved quantities for the singular Lagrange system. The determining equations, ...The invariance of the ordinary differential equations under the infinitesimal transformations was used to study the Lie symmetries and conserved quantities for the singular Lagrange system. The determining equations, the restriction equations of the Lie symmetries and the form of conserved quantities of the system are obtained.展开更多
This paper presents a new method to seek the conserved quantity from a Lie symmetry without using either Lagrangians or Hamiltonians for nonholonomic systems. The differential equations of motion of the systems are es...This paper presents a new method to seek the conserved quantity from a Lie symmetry without using either Lagrangians or Hamiltonians for nonholonomic systems. The differential equations of motion of the systems are established. The definition of the Lie symmetrical transformations of the systems is given, which only depends upon the infinitesimal transformations of groups for the generalized coordinates. The conserved quantity is directly constructed in terms of the Lie symmetry of the systems. The condition under which the Lie symmetry can lead to the conserved quantity and the form of the conserved quantity are obtained. Finally, an example is given to illustrate the application of the result.展开更多
Aim To study the Lie symmetries and conserved quantities of holonomic mechanical systems in terms of qnasi-coordinates. Methods The definition of an infinitesimal generator for the holonomic mechanical systems in te...Aim To study the Lie symmetries and conserved quantities of holonomic mechanical systems in terms of qnasi-coordinates. Methods The definition of an infinitesimal generator for the holonomic mechanical systems in terms of quasi-coordinates was given. Lie's method of the invariance of ordinary differential equations under infinitesimal transformations was used. Results and Conclusion The determining equations of the Lie symmetries of holonomic mechanical systems in terms of quassi-coordinates are established. The structure equation and the form of conserved quantities are obtained. An example to illustrate the applicaiton of the result is given.展开更多
基金National Natural Science Foundation of China, grant number 52177074.
文摘With the evolution of DC distribution networks from traditional radial topologies to more complex multi-branch structures,the number of measurement points supporting synchronous communication remains relatively limited.This poses challenges for conventional fault distance estimation methods,which are often tailored to simple topologies and are thus difficult to apply to large-scale,multi-node DC networks.To address this,a fault distance estimation method based on sparse measurement of high-frequency electrical quantities is proposed in this paper.First,a preliminary fault line identification model based on compressed sensing is constructed to effectively narrow the fault search range and improve localization efficiency.Then,leveraging the high-frequency impedance characteristics and the voltage-current relationship of electrical quantities,a fault distance estimation approach based on high-frequency measurements from both ends of a line is designed.This enables accurate distance estimation even when the measurement devices are not directly placed at both ends of the faulted line,overcoming the dependence on specific sensor placement inherent in traditional methods.Finally,to further enhance accuracy,an optimization model based on minimizing the high-frequency voltage error at the fault point is introduced to reduce estimation error.Simulation results demonstrate that the proposed method achieves a fault distance estimation error of less than 1%under normal conditions,and maintains good performance even under adverse scenarios.
基金The National Natural Science Foundation of China(No.71271053,71071032)the Scientific Innovation Research of College Graduates in Jiangsu Province(No.CXZZ12_0093)
文摘In order to obtain related brain electrical components and neural bases of physiology assessment of icon elements in a digital human-computer interface the modified sample-delay matching task experimental paradigm is used under different time pressures 4 000 and 2 000 ms and different icon quantities three five and ten icons on icon memory based on event-related potential ERP technology.Experimental results demonstrate that P300 has significant volatility changes and the maximum amplitude around the middle line of the parietal area PZ and P200 has obvious volatility changes around the middle line of the frontal and central area FCZ during icon cognition.P300 and P200 amplitudes increase as tasks become more difficult.Thus P300 latency is positively correlated with task difficulty. ERP research on the characteristics of icon memory will be an important reference standard in guiding user neurocognitive behavior and physiology assessment on interface usability.
文摘The invariance of the ordinary differential equations under the infinitesimal transformations was used to study the Lie symmetries and conserved quantities for the singular Lagrange system. The determining equations, the restriction equations of the Lie symmetries and the form of conserved quantities of the system are obtained.
文摘This paper presents a new method to seek the conserved quantity from a Lie symmetry without using either Lagrangians or Hamiltonians for nonholonomic systems. The differential equations of motion of the systems are established. The definition of the Lie symmetrical transformations of the systems is given, which only depends upon the infinitesimal transformations of groups for the generalized coordinates. The conserved quantity is directly constructed in terms of the Lie symmetry of the systems. The condition under which the Lie symmetry can lead to the conserved quantity and the form of the conserved quantity are obtained. Finally, an example is given to illustrate the application of the result.
文摘Aim To study the Lie symmetries and conserved quantities of holonomic mechanical systems in terms of qnasi-coordinates. Methods The definition of an infinitesimal generator for the holonomic mechanical systems in terms of quasi-coordinates was given. Lie's method of the invariance of ordinary differential equations under infinitesimal transformations was used. Results and Conclusion The determining equations of the Lie symmetries of holonomic mechanical systems in terms of quassi-coordinates are established. The structure equation and the form of conserved quantities are obtained. An example to illustrate the applicaiton of the result is given.
