Before emancipation, most balck women worked for the whites as domestic slaves; After emancipation, most balck women, as domestic emloyees, still had to do hard domestic work for survival, though they had a little fre...Before emancipation, most balck women worked for the whites as domestic slaves; After emancipation, most balck women, as domestic emloyees, still had to do hard domestic work for survival, though they had a little freedom and property. Balck women's identities changed literally, but the social hierarchy of whites'supremacy to blacks and men's supremacy to women still unchanged.展开更多
Slave-particle method is a powerful tool to tackle the correlation effect in quantum many-body physics. Although it has been successfully used to comprehend various intriguing problems, such as Mott metal-insulator tr...Slave-particle method is a powerful tool to tackle the correlation effect in quantum many-body physics. Although it has been successfully used to comprehend various intriguing problems, such as Mott metal-insulator transition and Kondo effect, there is still no convincing theory so far on the availability and limitation of this method. The abuse of slave-particle method may lead to wrong physics. As the simplest slave-particle method, Z2 slave spin, which is widely applied to many strongly correlated problems, is highly accessible and researchable. In this work, we will uncover the nature of the Z2 slave-spin method by studying a two-site Hubbard model. After exploring aspects of properties of this toy model, we make a comparative analysis of the results obtained by three methods:(i) slave-spin method on mean-field level,(ii) slave-spin method with gauge constraint, and(iii) the exact solution as a benchmark. We find that, protected by the particle-hole symmetry, the slave-spin mean-field method can recover the static properties of ground state exactly at half filling. Furthermore, in the parameter space where both U and T are small enough, the slave-spin mean-field method is also reliable in calculating the dynamic and thermal dynamic properties. However, when U or T is considerably large, the mean-field approximation gives ill-defined behaviors, which result from the unphysical states in the enlarged Hilbert space.These findings lead to our conclusion that the accuracy of slave particle can be guaranteed if we can exclude all unphysical states by enforcing gauge constraints. Our work demonstrates the promising prospect of slave-particle method in studying complex strongly correlated models with specific symmetry or in certain parameter space.展开更多
Neo-slave narratives avoid being tied to origins by the apronstrings of the past, or being appropriated ahistorically, by a deliberate formal attempt to muddy all notions of origins. Tactics include deliberately misle...Neo-slave narratives avoid being tied to origins by the apronstrings of the past, or being appropriated ahistorically, by a deliberate formal attempt to muddy all notions of origins. Tactics include deliberately misleading intertextuality; ″time-loop paradox″; time travel; anachronism; and the deliberate erasure of the historical record, using the conventions of genre to undermine the assumption that in the globalised marketplace all consumers are equal and all cultures available for consumption.展开更多
This paper addresses a master-slave synchro- nization strategy for complex dynamic systems based on feedback control. This strategy is applied to 3-DOF pla- nar manipulators in order to obtain synchronization in such ...This paper addresses a master-slave synchro- nization strategy for complex dynamic systems based on feedback control. This strategy is applied to 3-DOF pla- nar manipulators in order to obtain synchronization in such complicated as chaotic motions of end-effectors. A chaotic curve is selected from Duffing equation as the trajectory of master end-effector and a piecewise approximation method is proposed to accurately represent this chaotic trajectory of end-effectors. The dynamical equations of master-slave manipulators with synchronization controller are derived, and the Lyapunov stability theory is used to determine the stability of this controlled synchronization system. In numer- ical experiments, the synchronous motions of end-effectors as well as three joint angles and torques of master-slave manipulators are studied under the control of the proposed synchronization strategy. It is found that the positive gain matrix affects the implementation of synchronization con- trol strategy. This synchronization control strategy proves the synchronization＇s feasibility and controllability for com- plicated motions generated by master-slave manipulators.展开更多
In order to make the manipulators useful, some force feedback is required to enable the operator to sense the robot’s feelings. Without force feedback, many tasks will not be able to be carried out. For these reasons...In order to make the manipulators useful, some force feedback is required to enable the operator to sense the robot’s feelings. Without force feedback, many tasks will not be able to be carried out. For these reasons, a master slave system with different kinematics has been developed. The system permits us to vary the ratio of the position/attitude, to design a master manipulator without considering the kinematics of the slave manipulator, and so on. To overcome the difficulties, a master slave manipulator system with different kinematics is proposed. The master manipulator is force controlled via a force torque sensor in the handle. As to master slave manipulator system with two way force feedback is concerned, the force goes to the actuator from the operator, and come back to the operator from the actuator. The working situation is viewed by the stereo TV supervisory system. The force and vision telepresence are thus achieved. In order to ensure the maneuverability, direct drive DC motors and PWM servo units are adopted to improve the response speed. It can provide force response in a wide range. A lot of experiments were performed with the master slave manipulator system force telepresence to study the force response under restricted environment. By two force sensors, the force position bilateral force response system effectively decreases the affection of friction and inertia force, and increases the authenticity of bilateral force response. When the slave manipulator arm is encountered with soft object(sponge), in the experiments, the operator can clearly have the fine feeling as if he himself is contacted with the object.展开更多
In this paper, a successfully studied and developed master - slave muld - microcomputers control system based on PC - BUS for hollow spindle fancy yarn spinning machine, mainly Its overall scheme, software and hardwar...In this paper, a successfully studied and developed master - slave muld - microcomputers control system based on PC - BUS for hollow spindle fancy yarn spinning machine, mainly Its overall scheme, software and hardware construction, is introduced. Spinning experiments show that the system achieves satisfactory result. This system can solve the diftkultles of mechatronical fusion between domestic hollow splndk fancy yarn spuming muchine and its microcomputer control technology.展开更多
The networked synchronization problem of a class of master-slave chaotic systems with time-varying communication topologies is investigated in this paper. Based on algebraic graph theory and matrix theory, a simple li...The networked synchronization problem of a class of master-slave chaotic systems with time-varying communication topologies is investigated in this paper. Based on algebraic graph theory and matrix theory, a simple linear state feedback controller is designed to synchronize the master chaotic system and the slave chaotic systems with a time- varying communication topology connection. The exponential stability of the closed-loop networked synchronization error system is guaranteed by applying Lyapunov stability theory. The derived novel criteria are in the form of linear matrix inequalities （LMIs）, which are easy to examine and tremendously reduce the computation burden from the feedback matrices. This paper provides an alternative networked secure communication scheme which can be extended conveniently. An illustrative example is given to demonstrate the effectiveness of the proposed networked synchronization method.展开更多
文摘Before emancipation, most balck women worked for the whites as domestic slaves; After emancipation, most balck women, as domestic emloyees, still had to do hard domestic work for survival, though they had a little freedom and property. Balck women's identities changed literally, but the social hierarchy of whites'supremacy to blacks and men's supremacy to women still unchanged.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11674139,11704166,and 11834005)the Fundamental Research Funds for the Central Universities,ChinaProgram for Changjiang Scholars and Innovative Research Team in University,China(Grant No.IRT-16R35)
文摘Slave-particle method is a powerful tool to tackle the correlation effect in quantum many-body physics. Although it has been successfully used to comprehend various intriguing problems, such as Mott metal-insulator transition and Kondo effect, there is still no convincing theory so far on the availability and limitation of this method. The abuse of slave-particle method may lead to wrong physics. As the simplest slave-particle method, Z2 slave spin, which is widely applied to many strongly correlated problems, is highly accessible and researchable. In this work, we will uncover the nature of the Z2 slave-spin method by studying a two-site Hubbard model. After exploring aspects of properties of this toy model, we make a comparative analysis of the results obtained by three methods:(i) slave-spin method on mean-field level,(ii) slave-spin method with gauge constraint, and(iii) the exact solution as a benchmark. We find that, protected by the particle-hole symmetry, the slave-spin mean-field method can recover the static properties of ground state exactly at half filling. Furthermore, in the parameter space where both U and T are small enough, the slave-spin mean-field method is also reliable in calculating the dynamic and thermal dynamic properties. However, when U or T is considerably large, the mean-field approximation gives ill-defined behaviors, which result from the unphysical states in the enlarged Hilbert space.These findings lead to our conclusion that the accuracy of slave particle can be guaranteed if we can exclude all unphysical states by enforcing gauge constraints. Our work demonstrates the promising prospect of slave-particle method in studying complex strongly correlated models with specific symmetry or in certain parameter space.
文摘Neo-slave narratives avoid being tied to origins by the apronstrings of the past, or being appropriated ahistorically, by a deliberate formal attempt to muddy all notions of origins. Tactics include deliberately misleading intertextuality; ″time-loop paradox″; time travel; anachronism; and the deliberate erasure of the historical record, using the conventions of genre to undermine the assumption that in the globalised marketplace all consumers are equal and all cultures available for consumption.
基金supported by the Key Project of Chinese Ministry of Education(108037)the National Natural Science Foundation of China(10402008 and 50535010)
文摘This paper addresses a master-slave synchro- nization strategy for complex dynamic systems based on feedback control. This strategy is applied to 3-DOF pla- nar manipulators in order to obtain synchronization in such complicated as chaotic motions of end-effectors. A chaotic curve is selected from Duffing equation as the trajectory of master end-effector and a piecewise approximation method is proposed to accurately represent this chaotic trajectory of end-effectors. The dynamical equations of master-slave manipulators with synchronization controller are derived, and the Lyapunov stability theory is used to determine the stability of this controlled synchronization system. In numer- ical experiments, the synchronous motions of end-effectors as well as three joint angles and torques of master-slave manipulators are studied under the control of the proposed synchronization strategy. It is found that the positive gain matrix affects the implementation of synchronization con- trol strategy. This synchronization control strategy proves the synchronization＇s feasibility and controllability for com- plicated motions generated by master-slave manipulators.
文摘In order to make the manipulators useful, some force feedback is required to enable the operator to sense the robot’s feelings. Without force feedback, many tasks will not be able to be carried out. For these reasons, a master slave system with different kinematics has been developed. The system permits us to vary the ratio of the position/attitude, to design a master manipulator without considering the kinematics of the slave manipulator, and so on. To overcome the difficulties, a master slave manipulator system with different kinematics is proposed. The master manipulator is force controlled via a force torque sensor in the handle. As to master slave manipulator system with two way force feedback is concerned, the force goes to the actuator from the operator, and come back to the operator from the actuator. The working situation is viewed by the stereo TV supervisory system. The force and vision telepresence are thus achieved. In order to ensure the maneuverability, direct drive DC motors and PWM servo units are adopted to improve the response speed. It can provide force response in a wide range. A lot of experiments were performed with the master slave manipulator system force telepresence to study the force response under restricted environment. By two force sensors, the force position bilateral force response system effectively decreases the affection of friction and inertia force, and increases the authenticity of bilateral force response. When the slave manipulator arm is encountered with soft object(sponge), in the experiments, the operator can clearly have the fine feeling as if he himself is contacted with the object.
文摘In this paper, a successfully studied and developed master - slave muld - microcomputers control system based on PC - BUS for hollow spindle fancy yarn spinning machine, mainly Its overall scheme, software and hardware construction, is introduced. Spinning experiments show that the system achieves satisfactory result. This system can solve the diftkultles of mechatronical fusion between domestic hollow splndk fancy yarn spuming muchine and its microcomputer control technology.
基金supported by the National Natural Science Foundation of China (Grant Nos. 60904046, 60972164, 60974071, and 60804006)the Special Fund for Basic Scientific Research of Central Colleges, Northeastern University, China (Grant No. 090604005)+2 种基金the Science and Technology Program of Shenyang (Grant No. F11-264-1-70)the Program for Liaoning Excellent Talents in University (Grant No. LJQ2011137)the Program for Liaoning Innovative Research Team in University (Grant No. LT2011019)
文摘The networked synchronization problem of a class of master-slave chaotic systems with time-varying communication topologies is investigated in this paper. Based on algebraic graph theory and matrix theory, a simple linear state feedback controller is designed to synchronize the master chaotic system and the slave chaotic systems with a time- varying communication topology connection. The exponential stability of the closed-loop networked synchronization error system is guaranteed by applying Lyapunov stability theory. The derived novel criteria are in the form of linear matrix inequalities （LMIs）, which are easy to examine and tremendously reduce the computation burden from the feedback matrices. This paper provides an alternative networked secure communication scheme which can be extended conveniently. An illustrative example is given to demonstrate the effectiveness of the proposed networked synchronization method.
