Considering the situation that it is difficult to control the stability of narrow coal pillar in gob-side entry driving under unstable overlying strata, the finite difference numerical simulation method was adopted to...Considering the situation that it is difficult to control the stability of narrow coal pillar in gob-side entry driving under unstable overlying strata, the finite difference numerical simulation method was adopted to analyze the inner stress distribution and its evolution regularity, as well as the deformation characteristics of narrow coal pillar in gob-side entry driving, in the whole process from entry driving of last working face to the present working face mining. A new method of narrow coal pillar control based on the triune coupling support technique (TCST), which includes that high-strength prestressed thread steel bolt is used to strain the coal on the goaf side, and that short bolt to control the integrity of global displacement zone in coal pillar on the entry side, and that long grouting cable to fix anchor point to constrain the bed separation between global displacement zone and fixed zone, is thereby generated and applied to the field production. The result indicates that after entry excavating along the gob under unstable overlying strata, the supporting structure left on the gob side of narrow coal pillar is basically invalid to maintain the coal-pillar stability, and the large deformation of the pillar on the gob side is evident. Except for the significant dynamic pressure appearing in the coal mining of last working face and overlying strata stabilizing process, the stress variation inside the coal pillar in other stages are rather steady, however, the stress expansion is obvious and the coal pillar continues to deform. Once the gob-side entry driving is completed, a global displacement zone on the entry side appears in the shallow part of the pillar, whereas, a relatively steady fixed zone staying almost still in gob-side entry driving and present working face mining is found in the deep part of the pillar. The application of TCST can not only avoid the failure of pillar supporting structure, but exert the supporting capacity of the bolting structure left in the pillar of last sublevel entry, thus to jointly maintain the stability of coal pillar.展开更多
We propose an effective mechanism to couple superconducting charge and flux qubits by using a quantized nanomechanical resonator. The coupling between the charge and flux qubits can be controlled by the external flux ...We propose an effective mechanism to couple superconducting charge and flux qubits by using a quantized nanomechanical resonator. The coupling between the charge and flux qubits can be controlled by the external flux of the charge qubit. Under the strong coupling limR, an iSWAP gate can be generated by this scheme. The experimental feasibility in our scheme is also presented.展开更多
Deep oil exploration coring technology cannot accurately maintain the in-situ pressure and temperature of samples, which leads to a distortion of deep oil and gas resource reserve evaluations based on conventional cor...Deep oil exploration coring technology cannot accurately maintain the in-situ pressure and temperature of samples, which leads to a distortion of deep oil and gas resource reserve evaluations based on conventional cores and cannot guide the development of deep oil and gas resources on Earth. The fundamental reason is the lack of temperature and pressure control in in-situ coring environments. In this paper, a pressure control method of a coring device is studied. The theory and method of deep intelligent temperature-pressure coupling control are innovatively proposed, and a multifield coupling dynamic sealing model is established. The optimal cardinality three term PID (Proportional-Integral-Differential) intelligent control algorithm of pressure system is developed. The temperature-pressure characteristic of the gas-liquid two-phase cavity is analyzed, and the pressure intelligent control is carried out based on three term PID control algorithms. An in-situ condition-preserved coring (ICP-Coring) device is developed, and an intelligent control system for the temperature and pressure of the coring device is designed and verified by experiments. The results show that the temperature-pressure coupling control system can effectively realize stable sealing under temperature-pressure fields of 140 MPa and 150 °C. The temperature-pressure coupling control method can accurately realize a constant pressure inside the coring device. The maximum working pressure is 140 MPa, and the effective pressure compensation range is 20 MPa. The numerical simulation experiment of pressure system control algorithm is carried out, and the optimal cardinality and three term coefficients are obtained. The pressure steady-state error is less than 0.01%. The method of temperature-pressure coupling control has guiding significance for coring device research, and is also the basis for temperature-pressure decoupling control in ICP-Coring.展开更多
We theoretically analyze the transient properties of a probe field absorption and dispersion in a coupled semiconductor double-quantum-dot nanostructure.We show that in the presence of the Gaussian laser beams,absorpt...We theoretically analyze the transient properties of a probe field absorption and dispersion in a coupled semiconductor double-quantum-dot nanostructure.We show that in the presence of the Gaussian laser beams,absorption and dispersion of the probe field can be dramatically influenced by the relative phase between applied fields and intensity of the Gaussian laser beams.Transient and steady-state behaviors of the probe field absorption and dispersion are discussed to estimate the required switching time.The estimated range is between 5-8 ps for subluminal to superluminal light propagation.展开更多
For general dynamic positioning systems,controllers are mainly based on the feedback of motions only in the horizontal plane.However,for marine structures with a small water plane area and low metacentric height,undes...For general dynamic positioning systems,controllers are mainly based on the feedback of motions only in the horizontal plane.However,for marine structures with a small water plane area and low metacentric height,undesirable surge and pitch oscillations may be induced by the thruster actions.In this paper,three control laws are investigated to suppress the induced pitch motion by adding pitch rate,pitch angle or pitch acceleration into the feedback control loop.Extensive numerical simulations are conducted with a semi-submersible platform for each control law.The influences of additional terms on surge−pitch coupled motions are analyzed in both frequency and time domain.The mechanical constraints of the thrust allocation and the frequency characters of external forces are simultaneously considered.It is concluded that adding pitch angle or pitch acceleration into the feedback loop changes the natural frequency in pitch,and its performance is highly dependent on the frequency distribution of external forces,while adding pitch rate into the feedback loop is always effective in mitigating surge−pitch coupled motions.展开更多
This paper investigates an analytical optimal pose tracking control problem for chaser spacecraft during the close-range proximity operations with a non-cooperative space target subject to attitude tumbling and unknow...This paper investigates an analytical optimal pose tracking control problem for chaser spacecraft during the close-range proximity operations with a non-cooperative space target subject to attitude tumbling and unknown orbital maneuvering.Firstly,the relative translational motion between the orbital target and the chaser spacecraft is described in the Line-of-Sight(LOS)coordinate frame along with attitude quaternion dynamics.Then,based on the coupled 6-Degree of Freedom(DOF)pose dynamic model,an analytical optimal control action consisting of constrained optimal control value,application time and its duration are proposed via exploring the iterative sequential action control algorithm.Meanwhile,the global closed-loop asymptotic stability of the proposed predictive control action is presented and discussed.Compared with traditional proximity control schemes,the highlighting advantages are that the application time and duration of the devised controller is applied discretely in light of the influence of the instantaneous pose configuration on the pose tracking performance with less energy consumptions rather than at each sample time.Finally,three groups of illustrative examples are organized to validate the effectiveness of the proposed analytical optimal pose tracking control scheme.展开更多
Tiltrotor aircraft have three flight modes: helicopter mode, airplane mode, and transition mode. A tiltrotor has characteristics of highly nonlinear, time-varying flight dynamics and inertial/-control couplings in it...Tiltrotor aircraft have three flight modes: helicopter mode, airplane mode, and transition mode. A tiltrotor has characteristics of highly nonlinear, time-varying flight dynamics and inertial/-control couplings in its transition mode. It can transit from the helicopter mode to the airplane mode by tilting its nacelles, and an effective controller is crucial to accomplish tilting transition missions. Longitudinal dynamic characteristics of the tiltrotor are described by a nonlinear Lagrangeform model, which takes into account inertial/control couplings and aerodynamic interferences.Reference commands for airspeed velocity and attitude in the transition mode are calculated dynamically by visiting a command library which is founded in advance by analyzing the flight envelope of the tiltrotor. A Time-Varying Linear(TVL) model is obtained using a Taylorexpansion based online linearization technique from the nonlinear model. Subsequently, based on an optimal control concept, an online optimization based control method with input constraints considered is proposed. To validate the proposed control method, three typical tilting transition missions are simulated using the nonlinear model of XV-15 tiltrotor aircraft. Simulation results show that the controller can be used to control the tiltrotor throughout its operating envelop which includes a transition flight, and can also deal with vertical gust disturbances.展开更多
An optomechanical cavity embedded with a V-type three-level atom is exploited to control single-photon transport in a one-dimensional waveguide. The effects of the atom–cavity detuning, the optomechanical effect,the ...An optomechanical cavity embedded with a V-type three-level atom is exploited to control single-photon transport in a one-dimensional waveguide. The effects of the atom–cavity detuning, the optomechanical effect,the coupling strengths between the cavity and the atom or the waveguide, and the atomic dissipation on the single-photon transport properties are analyzed systematically. Interestingly, the single-photon transmission spectra show multiple double electromagnetically induced transparency. Moreover, the double electromagnetically induced transparency can be switched to a single one by tuning the atom–cavity detuning.展开更多
Redirecting the flow of light on the basis of the absorption/gain properties of optical systems is of great interest in many research fields, ranging from optical routing to optical cloaking. In this paper we investig...Redirecting the flow of light on the basis of the absorption/gain properties of optical systems is of great interest in many research fields, ranging from optical routing to optical cloaking. In this paper we investigate the control of the direction of the light propagation through loss-induced absorption in passive linear coupled optical systems. The considered optical system consists of a mode-splitting resonant cavity formed by coupling a Fabry–Perot(FP) cavity with a ring resonator. The coalescence of the asymmetric resonances, generated through mode-splitting dynamics, is the spectral result of the parity time symmetry breaking at FP resonance wavelengths.For specific values of the FP overall loss, a predominant backward propagation in the FP ring resonator occurs.In fiber optics technology, this device shows an ability to invert the sense of propagation of the light, quantified through the contrast ratio, in the order of 20 dB. This value can be obtained by externally varying the FP loss coefficient for a fixed set of the other physical parameters of the FP ring resonator. Our results can open a new way toward novel high-performance optical modulation and routing schemes.展开更多
Turbulence drag reduction is of great significance for the range increase of hypersonic flight vehicles.The proposed velocity-temperature coupling control method(Liu et al,Phys Rev Fluids 6:044603,2021)is further exte...Turbulence drag reduction is of great significance for the range increase of hypersonic flight vehicles.The proposed velocity-temperature coupling control method(Liu et al,Phys Rev Fluids 6:044603,2021)is further extended to the hypersonic turbulent boundary layer.Direct numerical simulation results of four comparative cases show that the heated wall blowing achieves a drag reduction rate of 10.58%,which is about the sum of wall blowing(5.27%)and wall heating(6.35%).By evaluating the control efficiency,however,it is found that heated wall blowing is not as good as wall blowing and cannot obtain net energy saving rate.The modified FIK decompositions of skin friction coefficient indicate that the cliffy decrease of the mean convection term is the primary contribution for the drag reduction.Effects of the proposed control measure on turbu-lence statistics and coherent structures are also analyzed.Streamwise vortex is found to be away from the wall,thus leading to a lower friction drag.展开更多
基金supports from the National High Technology Research and Development Program of China (No. 2012AA062101)the Program for New Century Excellent Talents in University of Ministry of Education of China (No. NCET-10-0770)+1 种基金the Program Granted for Scientific Innovation Research of College Graduate in Jiangsu Province (No. CXZZ11-0309)the Priority Academic Program Development of Jiangsu Higher Education Institutions (No. SZBF2011-6-B35)
文摘Considering the situation that it is difficult to control the stability of narrow coal pillar in gob-side entry driving under unstable overlying strata, the finite difference numerical simulation method was adopted to analyze the inner stress distribution and its evolution regularity, as well as the deformation characteristics of narrow coal pillar in gob-side entry driving, in the whole process from entry driving of last working face to the present working face mining. A new method of narrow coal pillar control based on the triune coupling support technique (TCST), which includes that high-strength prestressed thread steel bolt is used to strain the coal on the goaf side, and that short bolt to control the integrity of global displacement zone in coal pillar on the entry side, and that long grouting cable to fix anchor point to constrain the bed separation between global displacement zone and fixed zone, is thereby generated and applied to the field production. The result indicates that after entry excavating along the gob under unstable overlying strata, the supporting structure left on the gob side of narrow coal pillar is basically invalid to maintain the coal-pillar stability, and the large deformation of the pillar on the gob side is evident. Except for the significant dynamic pressure appearing in the coal mining of last working face and overlying strata stabilizing process, the stress variation inside the coal pillar in other stages are rather steady, however, the stress expansion is obvious and the coal pillar continues to deform. Once the gob-side entry driving is completed, a global displacement zone on the entry side appears in the shallow part of the pillar, whereas, a relatively steady fixed zone staying almost still in gob-side entry driving and present working face mining is found in the deep part of the pillar. The application of TCST can not only avoid the failure of pillar supporting structure, but exert the supporting capacity of the bolting structure left in the pillar of last sublevel entry, thus to jointly maintain the stability of coal pillar.
文摘We propose an effective mechanism to couple superconducting charge and flux qubits by using a quantized nanomechanical resonator. The coupling between the charge and flux qubits can be controlled by the external flux of the charge qubit. Under the strong coupling limR, an iSWAP gate can be generated by this scheme. The experimental feasibility in our scheme is also presented.
基金supported by the National Natural Science Foundation of China(grant numbers 51827901,51805340)funded by the Program for Guangdong Introducing Innovative and Enterpreneurial Teams(No.2019ZT08G315)Shenzhen Basic Research Program(General Program)(No.JCYJ20190808153416970).
文摘Deep oil exploration coring technology cannot accurately maintain the in-situ pressure and temperature of samples, which leads to a distortion of deep oil and gas resource reserve evaluations based on conventional cores and cannot guide the development of deep oil and gas resources on Earth. The fundamental reason is the lack of temperature and pressure control in in-situ coring environments. In this paper, a pressure control method of a coring device is studied. The theory and method of deep intelligent temperature-pressure coupling control are innovatively proposed, and a multifield coupling dynamic sealing model is established. The optimal cardinality three term PID (Proportional-Integral-Differential) intelligent control algorithm of pressure system is developed. The temperature-pressure characteristic of the gas-liquid two-phase cavity is analyzed, and the pressure intelligent control is carried out based on three term PID control algorithms. An in-situ condition-preserved coring (ICP-Coring) device is developed, and an intelligent control system for the temperature and pressure of the coring device is designed and verified by experiments. The results show that the temperature-pressure coupling control system can effectively realize stable sealing under temperature-pressure fields of 140 MPa and 150 °C. The temperature-pressure coupling control method can accurately realize a constant pressure inside the coring device. The maximum working pressure is 140 MPa, and the effective pressure compensation range is 20 MPa. The numerical simulation experiment of pressure system control algorithm is carried out, and the optimal cardinality and three term coefficients are obtained. The pressure steady-state error is less than 0.01%. The method of temperature-pressure coupling control has guiding significance for coring device research, and is also the basis for temperature-pressure decoupling control in ICP-Coring.
文摘We theoretically analyze the transient properties of a probe field absorption and dispersion in a coupled semiconductor double-quantum-dot nanostructure.We show that in the presence of the Gaussian laser beams,absorption and dispersion of the probe field can be dramatically influenced by the relative phase between applied fields and intensity of the Gaussian laser beams.Transient and steady-state behaviors of the probe field absorption and dispersion are discussed to estimate the required switching time.The estimated range is between 5-8 ps for subluminal to superluminal light propagation.
基金the National Natural Science Foundation of China(Grant Nos.51179103 and 51979167)the Ministry of Industry and Information Technology(Grant No.[2016]22)the Hainan Provincial Joint Project of Sanya Bay Science and Technology City(Grant No.520LH051).
文摘For general dynamic positioning systems,controllers are mainly based on the feedback of motions only in the horizontal plane.However,for marine structures with a small water plane area and low metacentric height,undesirable surge and pitch oscillations may be induced by the thruster actions.In this paper,three control laws are investigated to suppress the induced pitch motion by adding pitch rate,pitch angle or pitch acceleration into the feedback control loop.Extensive numerical simulations are conducted with a semi-submersible platform for each control law.The influences of additional terms on surge−pitch coupled motions are analyzed in both frequency and time domain.The mechanical constraints of the thrust allocation and the frequency characters of external forces are simultaneously considered.It is concluded that adding pitch angle or pitch acceleration into the feedback loop changes the natural frequency in pitch,and its performance is highly dependent on the frequency distribution of external forces,while adding pitch rate into the feedback loop is always effective in mitigating surge−pitch coupled motions.
基金This study was co-supported by the National Natural Science Foundation of China(Nos.62003371,62373379,62103446,61273351,62073343)the Outstanding Youth Fund of Hunan Provincial Natural Science,China(No.2022JJ20081)the Innovation Driven Project of Central South University,China(No.2023CXQD066).
文摘This paper investigates an analytical optimal pose tracking control problem for chaser spacecraft during the close-range proximity operations with a non-cooperative space target subject to attitude tumbling and unknown orbital maneuvering.Firstly,the relative translational motion between the orbital target and the chaser spacecraft is described in the Line-of-Sight(LOS)coordinate frame along with attitude quaternion dynamics.Then,based on the coupled 6-Degree of Freedom(DOF)pose dynamic model,an analytical optimal control action consisting of constrained optimal control value,application time and its duration are proposed via exploring the iterative sequential action control algorithm.Meanwhile,the global closed-loop asymptotic stability of the proposed predictive control action is presented and discussed.Compared with traditional proximity control schemes,the highlighting advantages are that the application time and duration of the devised controller is applied discretely in light of the influence of the instantaneous pose configuration on the pose tracking performance with less energy consumptions rather than at each sample time.Finally,three groups of illustrative examples are organized to validate the effectiveness of the proposed analytical optimal pose tracking control scheme.
基金supported by the National Natural Science Foundation of China (No. 11502008)
文摘Tiltrotor aircraft have three flight modes: helicopter mode, airplane mode, and transition mode. A tiltrotor has characteristics of highly nonlinear, time-varying flight dynamics and inertial/-control couplings in its transition mode. It can transit from the helicopter mode to the airplane mode by tilting its nacelles, and an effective controller is crucial to accomplish tilting transition missions. Longitudinal dynamic characteristics of the tiltrotor are described by a nonlinear Lagrangeform model, which takes into account inertial/control couplings and aerodynamic interferences.Reference commands for airspeed velocity and attitude in the transition mode are calculated dynamically by visiting a command library which is founded in advance by analyzing the flight envelope of the tiltrotor. A Time-Varying Linear(TVL) model is obtained using a Taylorexpansion based online linearization technique from the nonlinear model. Subsequently, based on an optimal control concept, an online optimization based control method with input constraints considered is proposed. To validate the proposed control method, three typical tilting transition missions are simulated using the nonlinear model of XV-15 tiltrotor aircraft. Simulation results show that the controller can be used to control the tiltrotor throughout its operating envelop which includes a transition flight, and can also deal with vertical gust disturbances.
基金partially supported by the National Natural Science Foundation of China(Nos.11504104,11447221,and 11274148)the Scientific Research Fundof Hunan Provincial Education Department(No.15C0539)+2 种基金the Natural Science Foundation of Hunan Province(No.2015JJ6035)the National Natural Science Foundation of China for Fostering Talents in Basic Research(No.11405052)the Key Laboratory of Low Dimensional Quantum Structures and Quantum Control(No.QSQC1409)
文摘An optomechanical cavity embedded with a V-type three-level atom is exploited to control single-photon transport in a one-dimensional waveguide. The effects of the atom–cavity detuning, the optomechanical effect,the coupling strengths between the cavity and the atom or the waveguide, and the atomic dissipation on the single-photon transport properties are analyzed systematically. Interestingly, the single-photon transmission spectra show multiple double electromagnetically induced transparency. Moreover, the double electromagnetically induced transparency can be switched to a single one by tuning the atom–cavity detuning.
文摘Redirecting the flow of light on the basis of the absorption/gain properties of optical systems is of great interest in many research fields, ranging from optical routing to optical cloaking. In this paper we investigate the control of the direction of the light propagation through loss-induced absorption in passive linear coupled optical systems. The considered optical system consists of a mode-splitting resonant cavity formed by coupling a Fabry–Perot(FP) cavity with a ring resonator. The coalescence of the asymmetric resonances, generated through mode-splitting dynamics, is the spectral result of the parity time symmetry breaking at FP resonance wavelengths.For specific values of the FP overall loss, a predominant backward propagation in the FP ring resonator occurs.In fiber optics technology, this device shows an ability to invert the sense of propagation of the light, quantified through the contrast ratio, in the order of 20 dB. This value can be obtained by externally varying the FP loss coefficient for a fixed set of the other physical parameters of the FP ring resonator. Our results can open a new way toward novel high-performance optical modulation and routing schemes.
基金the National Natural Science Foundation of China(Grant Nos.12202488 and 12072306)Natural Science Program of NUDT(ZK22-30)Independent Cultivation Project for Young Talents of the College of Aerospace Science and Engineering.
文摘Turbulence drag reduction is of great significance for the range increase of hypersonic flight vehicles.The proposed velocity-temperature coupling control method(Liu et al,Phys Rev Fluids 6:044603,2021)is further extended to the hypersonic turbulent boundary layer.Direct numerical simulation results of four comparative cases show that the heated wall blowing achieves a drag reduction rate of 10.58%,which is about the sum of wall blowing(5.27%)and wall heating(6.35%).By evaluating the control efficiency,however,it is found that heated wall blowing is not as good as wall blowing and cannot obtain net energy saving rate.The modified FIK decompositions of skin friction coefficient indicate that the cliffy decrease of the mean convection term is the primary contribution for the drag reduction.Effects of the proposed control measure on turbu-lence statistics and coherent structures are also analyzed.Streamwise vortex is found to be away from the wall,thus leading to a lower friction drag.