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
This study presents an achievement of laser cooling of alkaline-earth atoms in the Chinese Space Station’s strontium(Sr)atomic space optical clock.The system’s core components,physical unit,optical unit,and electric...This study presents an achievement of laser cooling of alkaline-earth atoms in the Chinese Space Station’s strontium(Sr)atomic space optical clock.The system’s core components,physical unit,optical unit,and electrical unit,have a total volume of 306 L and a total mass of 163.8 kg.These compact and robust units can overcome mechanical vibrations and temperature fluctuations during space launch.The laser sources of the optical unit are composed of diode lasers,and the injection locking of slave lasers is automatically performed by a program.In the experiment,a blue magneto-optical trap of cold atoms was achieved,with the atom numbers estimated to be approximately(1.50±0.13)×10^(6) for 87Sr and(8.00±0.56)×10^(6) for 88Sr.This work establishes a foundation for atomic confinement and high-precision interrogation in space-based optical clocks and expands the frontiers of cold atom physics in microgravity.展开更多
Master robots are integral components of teleoperated robot-assisted minimally invasive surgery systems.Among them,parallel mechanism-based 6-degree-of-freedom master robots are distinguished by low inertia and high-f...Master robots are integral components of teleoperated robot-assisted minimally invasive surgery systems.Among them,parallel mechanism-based 6-degree-of-freedom master robots are distinguished by low inertia and high-force feedback.However,complex kinematics and singularities are the main barriers limiting its usage.This study converts the Hexa-type 6-RUS mechanism into a master robot to construct master-slave teleoperation system.The clinical background is briefly introduced and a representative surgical robot is employed to analyze the master-slave mapping relationship.The inverse/forward kinematics,the Jacobian matrix,and the translation and orientation workspace are derived as the bases of master robot’s application.The architecture parameters are optimized by the global transmission index to achieve better motion/force transmissibility.Based on the optimal result,the prototype and the master-slave control loop are constructed.Finally,the corresponding master-slave teleoperation experiment and model experiment demonstrate that the proposed master robot satisfies the basic need for medical application.展开更多
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
With the Becchi-Rouet-Stora-Tyutin(BRST) quantization of gauge theory,we solve the long-standing difficult problem of the local constraint conditions,i.e.the single occupation of a slave particle per site,in the slave...With the Becchi-Rouet-Stora-Tyutin(BRST) quantization of gauge theory,we solve the long-standing difficult problem of the local constraint conditions,i.e.the single occupation of a slave particle per site,in the slave particle theory.This difficulty is actually caused by inconsistently dealing with the local Lagrange multiplier λ_(i) which ensures the constraint:in the Hamiltonian formalism of the theory,λ_(i) is time-independent and commutes with the Hamiltonian while in the Lagrangian formalism,λ_(i)(t) becomes time-dependent and plays a role of gauge field.This implies that the redundant degrees of freedom of λ_(i)(t) are introduced and must be removed by the additional constraint,the gauge fixing condition(GFC) ?_tλ_(i)(t)= 0.In literature,this GFC was missed.We add this GFC and use the BRST quantization of gauge theory for Dirac's first-class constraints in the slave particle theory.This GFC endows λ_(i)(t) with dynamics and leads to important physical results.As an example,we study the Hubbard model at half-filling and find that the spinon is gapped in the weak U and the system is indeed a conventional metal,which resolves the paradox that the weak coupling state is a superconductor in the previous slave boson mean field(MF) theory.For the t-J model,we find that the dynamic effect of λ_(i)(t) substantially suppresses the d-wave pairing gap and then the superconducting critical temperature may be lowered at least a factor of one-fifth of the MF value which is of the order of 1000 K.The renormalized T_c is then close to that in cuprates.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
As each cluster head(CH)sensor node is used to aggregate,fuse,and forward data from different sensor nodes in an underwater acoustic sensor network(UASN),guaranteeing the data security in a CH is very critical.In this...As each cluster head(CH)sensor node is used to aggregate,fuse,and forward data from different sensor nodes in an underwater acoustic sensor network(UASN),guaranteeing the data security in a CH is very critical.In this paper,a cooperative security monitoring mechanism aided by multiple slave cluster heads(SCHs)is proposed to keep track of the data security of a CH.By designing a low complexity“equilateral triangle algorithm(ETA)”,the optimal SCHs(named as ETA-based multiple SCHs)are selected from the candidate SCHs so as to improve the dispersion and coverage of SCHs and achieve largescale data security monitoring.In addition,by analyzing the entire monitoring process,the close form expression of the probability of the failure attack identification for the SCHs with respect to the probability of attack launched by ordinary nodes is deduced.The simulation results show that the proposed optimal ETA-based multiple SCH cooperation scheme has lower probability of the failure attack identification than that of the existing schemes.In addition,the numerical simulation results are consistent with the theoretical analysis results,thus verifying the effectiveness of the proposed scheme.展开更多
This article investigates the role of Portugal in the birth of the transatlantic slave trade.For a long time,most explanations of this traffic by American historians divorced the so-called“Old World”slave trade from...This article investigates the role of Portugal in the birth of the transatlantic slave trade.For a long time,most explanations of this traffic by American historians divorced the so-called“Old World”slave trade from the New World slave trade.This historiography blamed Christopher Columbus for the latter trade,while writing Portugal out of Atlantic history.Recent research,however,has shown that Portugal was the first country to claim the governance of the Atlantic Ocean and to trade in African slaves across the Atlantic.In an attempt to bring a much-needed African perspective to balance this Eurocentric debate,I question the notion of“trade”in the transatlantic slave trade.I suggest that this“trade”originated not in commerce,but in the Portuguese,pioneer role as slave raiders on the coast of Western Africa,a role spuriously justified by an invented Curse of Cain.The Pope confirmed this role with a bull granting Portugal exclusive rights to capture African slaves and trade them in Europe.This neglected original slave-raiding chapter is the precedent without which the transatlantic slave trade is dangerously misunderstood.展开更多
A microwave power-combining system composed of two Panasonic 2M244-M1 magnetrons based on master–slave injection-locking is demonstrated in this paper. The principle of master–slave injection-locking and the locking...A microwave power-combining system composed of two Panasonic 2M244-M1 magnetrons based on master–slave injection-locking is demonstrated in this paper. The principle of master–slave injection-locking and the locking condition are theoretical analyzed. Experimental results are consistent with the theoretical analysis and the experimental combined efficiency is higher than 96%. Compared with the external-injection-locked system, the power-combining based on the master–slave injection-locking magnetron is superior by taking out the external solid-state driver and the real-time phase control system. Thus, this power-combining system has great potential for obtaining a high efficiency, high stability, low cost, and high power microwave source.展开更多
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 Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB35010202)the National Natural Science Foundation of China(Grants No.62275268)。
文摘This study presents an achievement of laser cooling of alkaline-earth atoms in the Chinese Space Station’s strontium(Sr)atomic space optical clock.The system’s core components,physical unit,optical unit,and electrical unit,have a total volume of 306 L and a total mass of 163.8 kg.These compact and robust units can overcome mechanical vibrations and temperature fluctuations during space launch.The laser sources of the optical unit are composed of diode lasers,and the injection locking of slave lasers is automatically performed by a program.In the experiment,a blue magneto-optical trap of cold atoms was achieved,with the atom numbers estimated to be approximately(1.50±0.13)×10^(6) for 87Sr and(8.00±0.56)×10^(6) for 88Sr.This work establishes a foundation for atomic confinement and high-precision interrogation in space-based optical clocks and expands the frontiers of cold atom physics in microgravity.
基金the National Natural Science Foundation of China(No.62211540723)the Interdisciplinary Program of Shanghai Jiao Tong University(Nos.YG2023ZD05 and YG2023ZD14)+1 种基金the Quanzhou High-Level Talent Innovation and Entrepreneurship Project(No.2021C003R)the Research Project of Institute of Medical Robotics of Shanghai Jiao Tong University。
文摘Master robots are integral components of teleoperated robot-assisted minimally invasive surgery systems.Among them,parallel mechanism-based 6-degree-of-freedom master robots are distinguished by low inertia and high-force feedback.However,complex kinematics and singularities are the main barriers limiting its usage.This study converts the Hexa-type 6-RUS mechanism into a master robot to construct master-slave teleoperation system.The clinical background is briefly introduced and a representative surgical robot is employed to analyze the master-slave mapping relationship.The inverse/forward kinematics,the Jacobian matrix,and the translation and orientation workspace are derived as the bases of master robot’s application.The architecture parameters are optimized by the global transmission index to achieve better motion/force transmissibility.Based on the optimal result,the prototype and the master-slave control loop are constructed.Finally,the corresponding master-slave teleoperation experiment and model experiment demonstrate that the proposed master robot satisfies the basic need for medical application.
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With the Becchi-Rouet-Stora-Tyutin(BRST) quantization of gauge theory,we solve the long-standing difficult problem of the local constraint conditions,i.e.the single occupation of a slave particle per site,in the slave particle theory.This difficulty is actually caused by inconsistently dealing with the local Lagrange multiplier λ_(i) which ensures the constraint:in the Hamiltonian formalism of the theory,λ_(i) is time-independent and commutes with the Hamiltonian while in the Lagrangian formalism,λ_(i)(t) becomes time-dependent and plays a role of gauge field.This implies that the redundant degrees of freedom of λ_(i)(t) are introduced and must be removed by the additional constraint,the gauge fixing condition(GFC) ?_tλ_(i)(t)= 0.In literature,this GFC was missed.We add this GFC and use the BRST quantization of gauge theory for Dirac's first-class constraints in the slave particle theory.This GFC endows λ_(i)(t) with dynamics and leads to important physical results.As an example,we study the Hubbard model at half-filling and find that the spinon is gapped in the weak U and the system is indeed a conventional metal,which resolves the paradox that the weak coupling state is a superconductor in the previous slave boson mean field(MF) theory.For the t-J model,we find that the dynamic effect of λ_(i)(t) substantially suppresses the d-wave pairing gap and then the superconducting critical temperature may be lowered at least a factor of one-fifth of the MF value which is of the order of 1000 K.The renormalized T_c is then close to that in cuprates.
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.
基金supported in part by the Joint Fund of Science and Technology Department of Liaoning Province and State Key Laboratory of Robotics,China under Grant 2021-KF-22-08in part by the Basic Research Program of Science and Technology of Shenzhen,China under Grant JCYJ20190809161805508in part by the National Natural Science Foundation of China under Grant 62271423 and Grant 41976178.
文摘As each cluster head(CH)sensor node is used to aggregate,fuse,and forward data from different sensor nodes in an underwater acoustic sensor network(UASN),guaranteeing the data security in a CH is very critical.In this paper,a cooperative security monitoring mechanism aided by multiple slave cluster heads(SCHs)is proposed to keep track of the data security of a CH.By designing a low complexity“equilateral triangle algorithm(ETA)”,the optimal SCHs(named as ETA-based multiple SCHs)are selected from the candidate SCHs so as to improve the dispersion and coverage of SCHs and achieve largescale data security monitoring.In addition,by analyzing the entire monitoring process,the close form expression of the probability of the failure attack identification for the SCHs with respect to the probability of attack launched by ordinary nodes is deduced.The simulation results show that the proposed optimal ETA-based multiple SCH cooperation scheme has lower probability of the failure attack identification than that of the existing schemes.In addition,the numerical simulation results are consistent with the theoretical analysis results,thus verifying the effectiveness of the proposed scheme.
文摘This article investigates the role of Portugal in the birth of the transatlantic slave trade.For a long time,most explanations of this traffic by American historians divorced the so-called“Old World”slave trade from the New World slave trade.This historiography blamed Christopher Columbus for the latter trade,while writing Portugal out of Atlantic history.Recent research,however,has shown that Portugal was the first country to claim the governance of the Atlantic Ocean and to trade in African slaves across the Atlantic.In an attempt to bring a much-needed African perspective to balance this Eurocentric debate,I question the notion of“trade”in the transatlantic slave trade.I suggest that this“trade”originated not in commerce,but in the Portuguese,pioneer role as slave raiders on the coast of Western Africa,a role spuriously justified by an invented Curse of Cain.The Pope confirmed this role with a bull granting Portugal exclusive rights to capture African slaves and trade them in Europe.This neglected original slave-raiding chapter is the precedent without which the transatlantic slave trade is dangerously misunderstood.
基金Project supported by the National Basic Research Program of China(Grant No.2013CB328902)the National Natural Science Foundation of China(Grant No.61501311)
文摘A microwave power-combining system composed of two Panasonic 2M244-M1 magnetrons based on master–slave injection-locking is demonstrated in this paper. The principle of master–slave injection-locking and the locking condition are theoretical analyzed. Experimental results are consistent with the theoretical analysis and the experimental combined efficiency is higher than 96%. Compared with the external-injection-locked system, the power-combining based on the master–slave injection-locking magnetron is superior by taking out the external solid-state driver and the real-time phase control system. Thus, this power-combining system has great potential for obtaining a high efficiency, high stability, low cost, and high power microwave source.
