In order to obtain liquefied products with higher yields of aromatic molecules to produce mesophase pitch,a good understanding of the relevant reaction mechanisms is required.Reactive molecular dynamics simulations we...In order to obtain liquefied products with higher yields of aromatic molecules to produce mesophase pitch,a good understanding of the relevant reaction mechanisms is required.Reactive molecular dynamics simulations were used to study the thermal reactions of pyrene,1-methylpyrene,7,8,9,10-tetrahydrobenzopyrene,and mixtures of pyrene with 1-octene,cyclohexene,or styrene.The reactant conversion rates,reaction rates,and product distributions were calculated and compared,and the mechanisms were analyzed and discussed.The results demonstrated that methyl and naphthenic structures in aromatics might improve the conversion rates of reactants in hydrogen transfer processes,but their steric hindrances prohibited the generation of high polymers.The naphthenic structures could generate more free radicals and presented a more obvious inhibition effect on the condensation of polymers compared with the methyl side chains.It was discovered that when different olefins were mixed with pyrene,1-octene primarily underwent pyrolysis reactions,whereas cyclohexene mainly underwent hydrogen transfer reactions with pyrene and styrene,mostly producing superconjugated biradicals through condensation reactions with pyrene.In the mixture systems,the olefins scattered aromatic molecules,hindering the formation of pyrene trimers and higher polymers.According to the reactive molecular dynamics simulations,styrene may enhance the yield of dimer and enable the controlled polycondensation of pyrene.展开更多
We investigated the electric controllable spin-filtering effect in a zigzag phosphorene nanoribbon(ZPNR) based normal–antiferromagnet–normal junction. Two ferromagnets are closely coupled to the edges of the nanorib...We investigated the electric controllable spin-filtering effect in a zigzag phosphorene nanoribbon(ZPNR) based normal–antiferromagnet–normal junction. Two ferromagnets are closely coupled to the edges of the nanoribbon and form the edge-to-edge antiferromagnetism. Under an in-plane electric field, the two degenerate edge bands of the edge-to-edge antiferromagnet split into four spin-polarized sub-bands and a 100% spin-polarized current can be easily induced with the maximal conductance 2e~2/h. The spin polarization changes with the strength of the electric field and the exchange field,and changes sign at opposite electric fields. The spin-polarized current switches from one edge to the other by reversing the direction of the electric field. The edge current can also be controlled spatially by changing the electric potential of the scattering region. The manipulation of edge current is useful in spin-transfer-torque magnetic random-access memory and provides a practical way to develop controllable spintronic devices.展开更多
Phase-change material(PCM)is widely used in thermal management due to their unique thermal behavior.However,related research in thermal rectifier is mainly focused on exploring the principles at the fundamental device...Phase-change material(PCM)is widely used in thermal management due to their unique thermal behavior.However,related research in thermal rectifier is mainly focused on exploring the principles at the fundamental device level,which results in a gap to real applications.Here,we propose a controllable thermal rectification design towards building applications through the direct adhesion of composite thermal rectification material(TRM)based on PCM and reduced graphene oxide(rGO)aerogel to ordinary concrete walls(CWs).The design is evaluated in detail by combining experiments and finite element analysis.It is found that,TRM can regulate the temperature difference on both sides of the TRM/CWs system by thermal rectification.The difference in two directions reaches to 13.8 K at the heat flow of 80 W/m^(2).In addition,the larger the change of thermal conductivity before and after phase change of TRM is,the more effective it is for regulating temperature difference in two directions.The stated technology has a wide range of applications for the thermal energy control in buildings with specific temperature requirements.展开更多
The surface-enhanced Raman scattering(SERS) optical fiber probes were successfully prepared by self-assembling on polyelectrolyte multilayers. Gold nanorods(Au NRs) were used as SERS enhancement material to give excel...The surface-enhanced Raman scattering(SERS) optical fiber probes were successfully prepared by self-assembling on polyelectrolyte multilayers. Gold nanorods(Au NRs) were used as SERS enhancement material to give excellent biological affinity and stability to the SERS optical fiber probes. Au NRs were synthesized by seed growth method. The synergistic effect between AgNO_(3) and surfactant was investigated, and the highest yield was found when AgNO_(3) was 500 uL. Meanwhile, different SERS optical fiber probes were obtained by selecting silane coupling agent, polyelectrolyte multilayer and graphene oxide(GO) to treat quartz fiber. It was found that the SERS optical fiber probes obtained by the self-assembled on polyelectrolyte multilayers method performed better than those by other methods. In addition, Mapping was combined with finite element simulation to analyze the electromagnetic field distribution at the fiber end face.The electromagnetic field distribution of Au NRs was investigated, the difference of electromagnetic field intensity around the Au NRs with different arrangements was compared, the strongest signal was obtained when the Au NRs were head-to-head. Finally, sensitivity of the optimized SERS optical fiber probes could reach 10^(-9)mol/L, with excellent stability and repeatability.展开更多
Objective:The purpose of the study was to assess the clinical efficacy and safety of a combined perfusion suction platform with pressure feedback control function and an ureteroscopic suction sheath that can measure t...Objective:The purpose of the study was to assess the clinical efficacy and safety of a combined perfusion suction platform with pressure feedback control function and an ureteroscopic suction sheath that can measure the ureteropelvic pressure in implementing lithotripsies.Methods:Fifty-two patients who underwent lithotripsy under intelligent monitoring of ureteral intraluminal pressure from June 2016 to January 2018 were retrospectively recruited.The inclusion standard was stone diameter>1.5 cm but<2.5 cm.After the 12/14 Fr suction sheath was placed,manometer interface and suction interface of the sheath were connected to the platform via the pressure sensor and suction tube,respectively.The ureteroscope was connected to the platform perfusion pump,and the crushed stones were aspirated out under negative pressure.Results:According to the location of the stone,21(40.4%)cases were classified as upper ureteral stones,19(36.5%)were midureteral stones,and 12(23.1%)were lower ureteral stones.Forty-seven patients underwent successful primary sheath placement and lithotripsy with a mean operative time of 34.5(standard deviation 18.3)min.Retrograde stone migration did not occur.There were eight patients with hematuria postoperatively.Serious complication was 1.9% with one case of ureteral perforation.Stone clearance was 95.7% at Day 1e2 postoperatively,and 100% at Day 30 postoperatively.Conclusion:Ureteroscopic lithotripsy with intelligent pressure control using our device improved the efficiency of the lithotripsy and rate of stone clearance.The safety of the operation can be ensured.It is worth popularization and application in clinical practice.展开更多
The 20,000-ton combined train running has greatly promoted China’s heavy-haul railway transportation capability. The application of controllable train-tail devices could improve the braking wave of the train and brak...The 20,000-ton combined train running has greatly promoted China’s heavy-haul railway transportation capability. The application of controllable train-tail devices could improve the braking wave of the train and braking synchronism, and alleviate longitudinal impulse.However, the characteristics of the controllable train-tail device such as exhaust area, exhaust duration and exhaust action time are not uniform in practice, and their effects on the longitudinal impulse of the train are not apparent,which is worth studying. In this work, according to the formation of the Datong-Qinhuangdao Railway, the train air brake and longitudinal dynamics simulation system(TABLDSS) is applied to establish a 20,000-ton combined train model with the controllable train-tail device, and the braking characteristics and the longitudinal impulse of the train are calculated synchronously with changing the air exhaust time, exhaust area, and action lag time under initial braking. The results show that the maximum coupler force of the combined train will decrease with the extension of the continuous exhaust time, while the total exhaust time of the controllable train-tail device remains unchanged;the maximum coupler force of the combined train reduces by32.5% with the exhaust area increasing from 70% to 140%;when the lag time between the controllable train-tail device and the master locomotive is more than 1.5 s, the maximum coupler force of the train increases along with the time difference enlargement.展开更多
Reinforcement learning(RL) has roots in dynamic programming and it is called adaptive/approximate dynamic programming(ADP) within the control community. This paper reviews recent developments in ADP along with RL and ...Reinforcement learning(RL) has roots in dynamic programming and it is called adaptive/approximate dynamic programming(ADP) within the control community. This paper reviews recent developments in ADP along with RL and its applications to various advanced control fields. First, the background of the development of ADP is described, emphasizing the significance of regulation and tracking control problems. Some effective offline and online algorithms for ADP/adaptive critic control are displayed, where the main results towards discrete-time systems and continuous-time systems are surveyed, respectively.Then, the research progress on adaptive critic control based on the event-triggered framework and under uncertain environment is discussed, respectively, where event-based design, robust stabilization, and game design are reviewed. Moreover, the extensions of ADP for addressing control problems under complex environment attract enormous attention. The ADP architecture is revisited under the perspective of data-driven and RL frameworks,showing how they promote ADP formulation significantly.Finally, several typical control applications with respect to RL and ADP are summarized, particularly in the fields of wastewater treatment processes and power systems, followed by some general prospects for future research. Overall, the comprehensive survey on ADP and RL for advanced control applications has d emonstrated its remarkable potential within the artificial intelligence era. In addition, it also plays a vital role in promoting environmental protection and industrial intelligence.展开更多
Platooning represents one of the key features that connected automated vehicles may possess as it allows multiple automated vehicles to be maneuvered cooperatively with small headways on roads. However, a critical cha...Platooning represents one of the key features that connected automated vehicles may possess as it allows multiple automated vehicles to be maneuvered cooperatively with small headways on roads. However, a critical challenge in accomplishing automated vehicle platoons is to deal with the effects of intermittent and sporadic vehicle-to-vehicle data transmissions caused by limited wireless communication resources. This paper addresses the co-design problem of dynamic event-triggered communication scheduling and cooperative adaptive cruise control for a convoy of automated vehicles with diverse spacing policies. The central aim is to achieve automated vehicle platooning under various gap references with desired platoon stability and spacing performance requirements, while simultaneously improving communication efficiency. Toward this aim, a dynamic event-triggered scheduling mechanism is developed such that the intervehicle data transmissions are scheduled dynamically and efficiently over time. Then, a tractable co-design criterion on the existence of both the admissible event-driven cooperative adaptive cruise control law and the desired scheduling mechanism is derived. Finally, comparative simulation results are presented to substantiate the effectiveness and merits of the obtained results.展开更多
Phase change materials(PCMs)have attracted much attention in the field of solar thermal utilization recently,due to their outstanding thermal energy storage performance.However,PCMs usually release their stored latent...Phase change materials(PCMs)have attracted much attention in the field of solar thermal utilization recently,due to their outstanding thermal energy storage performance.However,PCMs usually release their stored latent heat spontaneously as the temperature below the phase transition temperature,rendering thermal energy storage and release uncontrollable,thus hindering their practical application in time and space.Herein,we developed erythritol/sodium carboxymethylcellulose/tetrasodium ethylenediaminetetraacetate(ERY/CMC/EDTA-4Na)composite PCMs with novel spatiotemporal thermal energy storage properties,defined as spatiotemporal PCMs(STPCMs),which exhibit the capacity of thermal energy long-term storage and controllable release.Our results show that the composite PCMs are unable to lose latent heat due to spontaneous crystallization during cooling,but can controllably release thermal energy through cold crystallization during reheating.The cold-crystallization temperature and enthalpy of composite PCMs can be adjusted by proportional addition of EDTA-4Na to the composite.When the mass fractions of CMC and EDTA-4Na are both 10%,the composite PCMs can exhibit the optical coldcrystallization temperature of 51.7℃ and enthalpy of 178.1 J/g.The supercooled composite PCMs without latent heat release can be maintained at room temperature(10-25℃)for up to more than two months,and subsequently the stored latent heat can be controllably released by means of thermal triggering or heterogeneous nucleation.Our findings provide novel insights into the design and construction of new PCMs with spatiotemporal performance of thermal energy long-term storage and controllable release,and consequently open a new door for the development of advanced solar thermal utilization techniques on the basis of STPCMs.展开更多
The dramatic increase in intracranial pressure after subarachnoid hemorrhage leads to a decrease in cerebral perfusion pressure and a reduction in cerebral blood flow.Mitochondria are directly affected by direct facto...The dramatic increase in intracranial pressure after subarachnoid hemorrhage leads to a decrease in cerebral perfusion pressure and a reduction in cerebral blood flow.Mitochondria are directly affected by direct factors such as ischemia,hypoxia,excitotoxicity,and toxicity of free hemoglobin and its degradation products,which trigger mitochondrial dysfunction.Dysfunctional mitochondria release large amounts of reactive oxygen species,inflammatory mediators,and apoptotic proteins that activate apoptotic pathways,further damaging cells.In response to this array of damage,cells have adopted multiple mitochondrial quality control mechanisms through evolution,including mitochondrial protein quality control,mitochondrial dynamics,mitophagy,mitochondrial biogenesis,and intercellular mitochondrial transfer,to maintain mitochondrial homeostasis under pathological conditions.Specific interventions targeting mitochondrial quality control mechanisms have emerged as promising therapeutic strategies for subarachnoid hemorrhage.This review provides an overview of recent research advances in mitochondrial pathophysiological processes after subarachnoid hemorrhage,particularly mitochondrial quality control mechanisms.It also presents potential therapeutic strategies to target mitochondrial quality control in subarachnoid hemorrhage.展开更多
Palladium(Pd)-based sulfides have triggered extensive interest due to their unique properties and potential applications in the fields of electronics and optoelectronics.However,the synthesis of large-scale uniform Pd...Palladium(Pd)-based sulfides have triggered extensive interest due to their unique properties and potential applications in the fields of electronics and optoelectronics.However,the synthesis of large-scale uniform PdS and PdS_(2)nanofilms(NFs)remains an enormous challenge.In this work,2-inch wafer-scale PdS and PdS_(2) NFs with excellent stability can be controllably prepared via chemical vapor deposition combined with electron beam evaporation technique.The thickness of the pre-deposited Pd film and the sulfurization temperature are critical for the precise synthesis of PdS and PdS_(2) NFs.A corresponding growth mechanism has been proposed based on our experimental results and Gibbs free energy calculations.The electrical transport properties of PdS and PdS_(2) NFs were explored by conductive atomic force microscopy.Our findings have achieved the controllable growth of PdS and PdS_(2) NFs,which may provide a pathway to facilitate PdS and PdS_(2) based applications for next-generation high performance optoelectronic devices.展开更多
In this tutorial paper, we explore the field of quantized feedback control, which has gained significant attention due to the growing prevalence of networked control systems. These systems require the transmission of ...In this tutorial paper, we explore the field of quantized feedback control, which has gained significant attention due to the growing prevalence of networked control systems. These systems require the transmission of feedback information, such as measurements and control signals, over digital networks, presenting novel challenges in estimation and control design. Our examination encompasses various topics, including the minimal information needed for effective feedback control, the design of quantizers, strategies for quantized control design and estimation,achieving consensus control with quantized data, and the pursuit of high-precision tracking using quantized measurements.展开更多
As a direct wide bandgap semiconductor,CsPbCl_(3)has great potential applications in the eld of near-ultraviolet photodetectors,lasers and higher-order multiphoton uores-cent detectors.In this work,we synthesized CsPb...As a direct wide bandgap semiconductor,CsPbCl_(3)has great potential applications in the eld of near-ultraviolet photodetectors,lasers and higher-order multiphoton uores-cent detectors.In this work,we synthesized CsPbCl_(3)micro/nanocrystals by vapor depo-sition method with CsCl and PbCl_(2)powders as the source materials.It was con rmed that the formation of CsPbCl_(3)perovskite through the chemical reaction of CsCl with PbCl_(2)occurred in the quartz boat before the source evaporation,not in vapor or on sub-strate surface.The evaporated CsPbCl_(3)can form micro/nanocrystals on substrate surfaces under appropriate conditions.Various morphologies including irregular polyhedrons,rods and pyramids could be observed at lower temperature,while stable and uniform CsPbCl_(3)single crystal microplatelets were controllably synthesized at 450℃.Prolonging the growth time could modulate the size and density of the microcrystals,but could not change the morphology.Substrate types made little di erence to the morphology of CsPbCl_(3)crystals.The photoluminescence spectra indicated that the crystallinity and morphology of CsPbCl_(3)micro/nanocrystals have signi cant e ects on their optical properties.The work is expected to be helpful to the development of optoelectronic devices based on individual CsPbCl_(3)microcrystal.展开更多
A novel 4H-Si C trench insulated gate bipolar transistor(IGBT)with a controllable hole-extracting(CHE)path is proposed and investigated in this paper.The CHE path is controlled by metal semiconductor gate(MES gate)and...A novel 4H-Si C trench insulated gate bipolar transistor(IGBT)with a controllable hole-extracting(CHE)path is proposed and investigated in this paper.The CHE path is controlled by metal semiconductor gate(MES gate)and metal oxide semiconductor gate(MOS gate)in the p-shield region.The grounded p-shield region can significantly suppress the high electric field around gate oxide in Si C devices,but it weakens the conductivity modulation in the Si C trench IGBT by rapidly sweeping out holes.This effect can be eliminated by introducing the CHE path.The CHE path is pinched off by the high gate bias voltage at on-state to maintain high conductivity modulation and obtain a comparatively low on-state voltage(VON).During the turn-off transient,the CHE path is formed,which contributes to a decreased turn-off loss(EOFF).Based on numerical simulation,the EOFFof the proposed IGBT is reduced by 89%compared with the conventional IGBT at the same VONand the VONof the proposed IGBT is reduced by 50%compared to the grounded p-shield IGBT at the same EOFF.In addition,the average power reduction for the proposed device can be 51.0%to 81.7%and 58.2%to 72.1%with its counterparts at a wide frequency range of 500 Hz to 10 k Hz,revealing a great improvement of frequency characteristics.展开更多
This paper studies the problem of time-varying formation control with finite-time prescribed performance for nonstrict feedback second-order multi-agent systems with unmeasured states and unknown nonlinearities.To eli...This paper studies the problem of time-varying formation control with finite-time prescribed performance for nonstrict feedback second-order multi-agent systems with unmeasured states and unknown nonlinearities.To eliminate nonlinearities,neural networks are applied to approximate the inherent dynamics of the system.In addition,due to the limitations of the actual working conditions,each follower agent can only obtain the locally measurable partial state information of the leader agent.To address this problem,a neural network state observer based on the leader state information is designed.Then,a finite-time prescribed performance adaptive output feedback control strategy is proposed by restricting the sliding mode surface to a prescribed region,which ensures that the closed-loop system has practical finite-time stability and that formation errors of the multi-agent systems converge to the prescribed performance bound in finite time.Finally,a numerical simulation is provided to demonstrate the practicality and effectiveness of the developed algorithm.展开更多
This paper proposes a novel event-driven encrypted control framework for linear networked control systems(NCSs),which relies on two modified uniform quantization policies,the Paillier cryptosystem,and an event-trigger...This paper proposes a novel event-driven encrypted control framework for linear networked control systems(NCSs),which relies on two modified uniform quantization policies,the Paillier cryptosystem,and an event-triggered strategy.Due to the fact that only integers can work in the Pailler cryptosystem,both the real-valued control gain and system state need to be first quantized before encryption.This is dramatically different from the existing quantized control methods,where only the quantization of a single value,e.g.,the control input or the system state,is considered.To handle this issue,static and dynamic quantization policies are presented,which achieve the desired integer conversions and guarantee asymptotic convergence of the quantized system state to the equilibrium.Then,the quantized system state is encrypted and sent to the controller when the triggering condition,specified by a state-based event-triggered strategy,is satisfied.By doing so,not only the security and confidentiality of data transmitted over the communication network are protected,but also the ciphertext expansion phenomenon can be relieved.Additionally,by tactfully designing the quantization sensitivities and triggering error,the proposed event-driven encrypted control framework ensures the asymptotic stability of the overall closedloop system.Finally,a simulation example of the secure motion control for an inverted pendulum cart system is presented to evaluate the effectiveness of the theoretical results.展开更多
This paper investigates the prescribed-time control(PTC) problem for a class of strict-feedback systems subject to non-vanishing uncertainties. The coexistence of mismatched uncertainties and non-vanishing disturbance...This paper investigates the prescribed-time control(PTC) problem for a class of strict-feedback systems subject to non-vanishing uncertainties. The coexistence of mismatched uncertainties and non-vanishing disturbances makes PTC synthesis nontrivial. In this work, a control method that does not involve infinite time-varying gain is proposed, leading to a practical and global prescribed time tracking control solution for the strict-feedback systems, in spite of both the mismatched and nonvanishing uncertainties. Different from methods based on control switching to avoid the issue of infinite control gain that involves control discontinuity at the switching point, in our method a softening unit is exclusively included to ensure the continuity of the control action. Furthermore, in contrast to most existing prescribed-time control works where the control scheme is only valid on a finite time interval, in this work, the proposed control scheme is valid on the entire time interval. In addition, the prior information on the upper or lower bound of gi is not in need,enlarging the applicability of the proposed method. Both the theoretical analysis and numerical simulation confirm the effectiveness of the proposed control algorithm.展开更多
Aiming at the tracking problem of a class of discrete nonaffine nonlinear multi-input multi-output(MIMO) repetitive systems subjected to separable and nonseparable disturbances, a novel data-driven iterative learning ...Aiming at the tracking problem of a class of discrete nonaffine nonlinear multi-input multi-output(MIMO) repetitive systems subjected to separable and nonseparable disturbances, a novel data-driven iterative learning control(ILC) scheme based on the zeroing neural networks(ZNNs) is proposed. First, the equivalent dynamic linearization data model is obtained by means of dynamic linearization technology, which exists theoretically in the iteration domain. Then, the iterative extended state observer(IESO) is developed to estimate the disturbance and the coupling between systems, and the decoupled dynamic linearization model is obtained for the purpose of controller synthesis. To solve the zero-seeking tracking problem with inherent tolerance of noise,an ILC based on noise-tolerant modified ZNN is proposed. The strict assumptions imposed on the initialization conditions of each iteration in the existing ILC methods can be absolutely removed with our method. In addition, theoretical analysis indicates that the modified ZNN can converge to the exact solution of the zero-seeking tracking problem. Finally, a generalized example and an application-oriented example are presented to verify the effectiveness and superiority of the proposed process.展开更多
This paper investigates the adaptive trajectory tracking control problem and the unknown parameter identification problem of a class of rotor-missiles with parametric system uncertainties.First,considering the uncerta...This paper investigates the adaptive trajectory tracking control problem and the unknown parameter identification problem of a class of rotor-missiles with parametric system uncertainties.First,considering the uncertainty of structural and aerodynamic parameters,the six-degree-of-freedom(6Do F) nonlinear equations describing the position and attitude dynamics of the rotor-missile are established,respectively,in the inertial and body-fixed reference frames.Next,a hierarchical adaptive trajectory tracking controller that can guarantee closed-loop stability is proposed according to the cascade characteristics of the 6Do F dynamics.Then,a memory-augmented update rule of unknown parameters is proposed by integrating all historical data of the regression matrix.As long as the finitely excited condition is satisfied,the precise identification of unknown parameters can be achieved.Finally,the validity of the proposed trajectory tracking controller and the parameter identification method is proved through Lyapunov stability theory and numerical simulations.展开更多
A quantum teleportation network involving multiple users is essential for future quantum internet.So far,controlled quantum teleportation has been demonstrated in a three-user network.However,versatile and controlled ...A quantum teleportation network involving multiple users is essential for future quantum internet.So far,controlled quantum teleportation has been demonstrated in a three-user network.However,versatile and controlled quantum teleportation network involving more users is in demand,which satisfies different combinations of users for practical requirements.Here we propose a highly versatile and controlled teleportation network that can switch among various combinations of different users.We use a single continuous-variable six-partite Greenberger-Horne-Zeilinger(GHZ)state to realize such a task by choosing the different measurement and feedback operations.The controlled teleportation network,which includes one sub-network,two sub-networks and three sub-networks,can be realized for different application of user combinations.Furthermore,the coherent feedback control(CFC)can manipulate and improve the teleportation performance.Our approach is flexible and scalable,and would provide a versatile platform for demonstrations of complex quantum communication and quantum computing protocols.展开更多
基金financially supported by the National Natural Science Foundation of China(Approval No.42172168).
文摘In order to obtain liquefied products with higher yields of aromatic molecules to produce mesophase pitch,a good understanding of the relevant reaction mechanisms is required.Reactive molecular dynamics simulations were used to study the thermal reactions of pyrene,1-methylpyrene,7,8,9,10-tetrahydrobenzopyrene,and mixtures of pyrene with 1-octene,cyclohexene,or styrene.The reactant conversion rates,reaction rates,and product distributions were calculated and compared,and the mechanisms were analyzed and discussed.The results demonstrated that methyl and naphthenic structures in aromatics might improve the conversion rates of reactants in hydrogen transfer processes,but their steric hindrances prohibited the generation of high polymers.The naphthenic structures could generate more free radicals and presented a more obvious inhibition effect on the condensation of polymers compared with the methyl side chains.It was discovered that when different olefins were mixed with pyrene,1-octene primarily underwent pyrolysis reactions,whereas cyclohexene mainly underwent hydrogen transfer reactions with pyrene and styrene,mostly producing superconjugated biradicals through condensation reactions with pyrene.In the mixture systems,the olefins scattered aromatic molecules,hindering the formation of pyrene trimers and higher polymers.According to the reactive molecular dynamics simulations,styrene may enhance the yield of dimer and enable the controlled polycondensation of pyrene.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.12174077 and 12174051)the Science Foundation of GuangDong Province (Grant No.2021A1515012363)GuangDong Basic and Applied Basic Research Foundation (Grant No.2022A1515110011)。
文摘We investigated the electric controllable spin-filtering effect in a zigzag phosphorene nanoribbon(ZPNR) based normal–antiferromagnet–normal junction. Two ferromagnets are closely coupled to the edges of the nanoribbon and form the edge-to-edge antiferromagnetism. Under an in-plane electric field, the two degenerate edge bands of the edge-to-edge antiferromagnet split into four spin-polarized sub-bands and a 100% spin-polarized current can be easily induced with the maximal conductance 2e~2/h. The spin polarization changes with the strength of the electric field and the exchange field,and changes sign at opposite electric fields. The spin-polarized current switches from one edge to the other by reversing the direction of the electric field. The edge current can also be controlled spatially by changing the electric potential of the scattering region. The manipulation of edge current is useful in spin-transfer-torque magnetic random-access memory and provides a practical way to develop controllable spintronic devices.
基金This work was supported in part by Tsinghua University-Zhuhai Huafa Industrial Share Company Joint Institute for Architecture Optoelectronic Technologies(JIAOT KF202204)in part by STI 2030—Major Projects under Grant 2022ZD0209200+2 种基金in part by National Natural Science Foundation of China under Grant 62374099,Grant 62022047in part by Beijing Natural Science-Xiaomi Innovation Joint Fund under Grant L233009in part by the Tsinghua-Toyota JointResearch Fund,in part by the Daikin-Tsinghua Union Program,in part sponsored by CIE-Tencent Robotics XRhino-Bird Focused Research Program.
文摘Phase-change material(PCM)is widely used in thermal management due to their unique thermal behavior.However,related research in thermal rectifier is mainly focused on exploring the principles at the fundamental device level,which results in a gap to real applications.Here,we propose a controllable thermal rectification design towards building applications through the direct adhesion of composite thermal rectification material(TRM)based on PCM and reduced graphene oxide(rGO)aerogel to ordinary concrete walls(CWs).The design is evaluated in detail by combining experiments and finite element analysis.It is found that,TRM can regulate the temperature difference on both sides of the TRM/CWs system by thermal rectification.The difference in two directions reaches to 13.8 K at the heat flow of 80 W/m^(2).In addition,the larger the change of thermal conductivity before and after phase change of TRM is,the more effective it is for regulating temperature difference in two directions.The stated technology has a wide range of applications for the thermal energy control in buildings with specific temperature requirements.
基金Funded by National Natural Science Foundation of China (Nos.51372179, 51772224)the Open Projects Foundation of Yangtze Optical Fiber and Cable Joint Stock Limited Company (YOFC)(No.SKLD1705)。
文摘The surface-enhanced Raman scattering(SERS) optical fiber probes were successfully prepared by self-assembling on polyelectrolyte multilayers. Gold nanorods(Au NRs) were used as SERS enhancement material to give excellent biological affinity and stability to the SERS optical fiber probes. Au NRs were synthesized by seed growth method. The synergistic effect between AgNO_(3) and surfactant was investigated, and the highest yield was found when AgNO_(3) was 500 uL. Meanwhile, different SERS optical fiber probes were obtained by selecting silane coupling agent, polyelectrolyte multilayer and graphene oxide(GO) to treat quartz fiber. It was found that the SERS optical fiber probes obtained by the self-assembled on polyelectrolyte multilayers method performed better than those by other methods. In addition, Mapping was combined with finite element simulation to analyze the electromagnetic field distribution at the fiber end face.The electromagnetic field distribution of Au NRs was investigated, the difference of electromagnetic field intensity around the Au NRs with different arrangements was compared, the strongest signal was obtained when the Au NRs were head-to-head. Finally, sensitivity of the optimized SERS optical fiber probes could reach 10^(-9)mol/L, with excellent stability and repeatability.
基金This study was funded by Major Science and Technology Projects of Jiangxi Provincial Science and Technology Department(20152ACG70009).
文摘Objective:The purpose of the study was to assess the clinical efficacy and safety of a combined perfusion suction platform with pressure feedback control function and an ureteroscopic suction sheath that can measure the ureteropelvic pressure in implementing lithotripsies.Methods:Fifty-two patients who underwent lithotripsy under intelligent monitoring of ureteral intraluminal pressure from June 2016 to January 2018 were retrospectively recruited.The inclusion standard was stone diameter>1.5 cm but<2.5 cm.After the 12/14 Fr suction sheath was placed,manometer interface and suction interface of the sheath were connected to the platform via the pressure sensor and suction tube,respectively.The ureteroscope was connected to the platform perfusion pump,and the crushed stones were aspirated out under negative pressure.Results:According to the location of the stone,21(40.4%)cases were classified as upper ureteral stones,19(36.5%)were midureteral stones,and 12(23.1%)were lower ureteral stones.Forty-seven patients underwent successful primary sheath placement and lithotripsy with a mean operative time of 34.5(standard deviation 18.3)min.Retrograde stone migration did not occur.There were eight patients with hematuria postoperatively.Serious complication was 1.9% with one case of ureteral perforation.Stone clearance was 95.7% at Day 1e2 postoperatively,and 100% at Day 30 postoperatively.Conclusion:Ureteroscopic lithotripsy with intelligent pressure control using our device improved the efficiency of the lithotripsy and rate of stone clearance.The safety of the operation can be ensured.It is worth popularization and application in clinical practice.
基金China National Railway Group Co.,Ltd(N2020J037).
文摘The 20,000-ton combined train running has greatly promoted China’s heavy-haul railway transportation capability. The application of controllable train-tail devices could improve the braking wave of the train and braking synchronism, and alleviate longitudinal impulse.However, the characteristics of the controllable train-tail device such as exhaust area, exhaust duration and exhaust action time are not uniform in practice, and their effects on the longitudinal impulse of the train are not apparent,which is worth studying. In this work, according to the formation of the Datong-Qinhuangdao Railway, the train air brake and longitudinal dynamics simulation system(TABLDSS) is applied to establish a 20,000-ton combined train model with the controllable train-tail device, and the braking characteristics and the longitudinal impulse of the train are calculated synchronously with changing the air exhaust time, exhaust area, and action lag time under initial braking. The results show that the maximum coupler force of the combined train will decrease with the extension of the continuous exhaust time, while the total exhaust time of the controllable train-tail device remains unchanged;the maximum coupler force of the combined train reduces by32.5% with the exhaust area increasing from 70% to 140%;when the lag time between the controllable train-tail device and the master locomotive is more than 1.5 s, the maximum coupler force of the train increases along with the time difference enlargement.
基金supported in part by the National Natural Science Foundation of China(62222301, 62073085, 62073158, 61890930-5, 62021003)the National Key Research and Development Program of China (2021ZD0112302, 2021ZD0112301, 2018YFC1900800-5)Beijing Natural Science Foundation (JQ19013)。
文摘Reinforcement learning(RL) has roots in dynamic programming and it is called adaptive/approximate dynamic programming(ADP) within the control community. This paper reviews recent developments in ADP along with RL and its applications to various advanced control fields. First, the background of the development of ADP is described, emphasizing the significance of regulation and tracking control problems. Some effective offline and online algorithms for ADP/adaptive critic control are displayed, where the main results towards discrete-time systems and continuous-time systems are surveyed, respectively.Then, the research progress on adaptive critic control based on the event-triggered framework and under uncertain environment is discussed, respectively, where event-based design, robust stabilization, and game design are reviewed. Moreover, the extensions of ADP for addressing control problems under complex environment attract enormous attention. The ADP architecture is revisited under the perspective of data-driven and RL frameworks,showing how they promote ADP formulation significantly.Finally, several typical control applications with respect to RL and ADP are summarized, particularly in the fields of wastewater treatment processes and power systems, followed by some general prospects for future research. Overall, the comprehensive survey on ADP and RL for advanced control applications has d emonstrated its remarkable potential within the artificial intelligence era. In addition, it also plays a vital role in promoting environmental protection and industrial intelligence.
基金supported in part by the Australian Research Council Discovery Early Career Researcher Award(DE200101128)。
文摘Platooning represents one of the key features that connected automated vehicles may possess as it allows multiple automated vehicles to be maneuvered cooperatively with small headways on roads. However, a critical challenge in accomplishing automated vehicle platoons is to deal with the effects of intermittent and sporadic vehicle-to-vehicle data transmissions caused by limited wireless communication resources. This paper addresses the co-design problem of dynamic event-triggered communication scheduling and cooperative adaptive cruise control for a convoy of automated vehicles with diverse spacing policies. The central aim is to achieve automated vehicle platooning under various gap references with desired platoon stability and spacing performance requirements, while simultaneously improving communication efficiency. Toward this aim, a dynamic event-triggered scheduling mechanism is developed such that the intervehicle data transmissions are scheduled dynamically and efficiently over time. Then, a tractable co-design criterion on the existence of both the admissible event-driven cooperative adaptive cruise control law and the desired scheduling mechanism is derived. Finally, comparative simulation results are presented to substantiate the effectiveness and merits of the obtained results.
基金the financial support from the Joint Fund of the Yulin University and the Dalian National Laboratory for Clean Energy(YLU-DNL Fund 2021007)the National Nature Science Foundation of China(21903082 and 22273100)+2 种基金the Dalian Institute of Chemical Physics(DICP I202036,and I202218)the DNL Cooperation Fund,CAS(DNL202012)Liaoning Provincial Natural Science Foundation of China under grant 2022-MS-020。
文摘Phase change materials(PCMs)have attracted much attention in the field of solar thermal utilization recently,due to their outstanding thermal energy storage performance.However,PCMs usually release their stored latent heat spontaneously as the temperature below the phase transition temperature,rendering thermal energy storage and release uncontrollable,thus hindering their practical application in time and space.Herein,we developed erythritol/sodium carboxymethylcellulose/tetrasodium ethylenediaminetetraacetate(ERY/CMC/EDTA-4Na)composite PCMs with novel spatiotemporal thermal energy storage properties,defined as spatiotemporal PCMs(STPCMs),which exhibit the capacity of thermal energy long-term storage and controllable release.Our results show that the composite PCMs are unable to lose latent heat due to spontaneous crystallization during cooling,but can controllably release thermal energy through cold crystallization during reheating.The cold-crystallization temperature and enthalpy of composite PCMs can be adjusted by proportional addition of EDTA-4Na to the composite.When the mass fractions of CMC and EDTA-4Na are both 10%,the composite PCMs can exhibit the optical coldcrystallization temperature of 51.7℃ and enthalpy of 178.1 J/g.The supercooled composite PCMs without latent heat release can be maintained at room temperature(10-25℃)for up to more than two months,and subsequently the stored latent heat can be controllably released by means of thermal triggering or heterogeneous nucleation.Our findings provide novel insights into the design and construction of new PCMs with spatiotemporal performance of thermal energy long-term storage and controllable release,and consequently open a new door for the development of advanced solar thermal utilization techniques on the basis of STPCMs.
基金supported by the National Natural Science Foundation of China,Nos.82130037(to CH),81971122(to CH),82171323(to WL)the Natural Science Foundation of Jiangsu Province of China,No.BK20201113(to WL)。
文摘The dramatic increase in intracranial pressure after subarachnoid hemorrhage leads to a decrease in cerebral perfusion pressure and a reduction in cerebral blood flow.Mitochondria are directly affected by direct factors such as ischemia,hypoxia,excitotoxicity,and toxicity of free hemoglobin and its degradation products,which trigger mitochondrial dysfunction.Dysfunctional mitochondria release large amounts of reactive oxygen species,inflammatory mediators,and apoptotic proteins that activate apoptotic pathways,further damaging cells.In response to this array of damage,cells have adopted multiple mitochondrial quality control mechanisms through evolution,including mitochondrial protein quality control,mitochondrial dynamics,mitophagy,mitochondrial biogenesis,and intercellular mitochondrial transfer,to maintain mitochondrial homeostasis under pathological conditions.Specific interventions targeting mitochondrial quality control mechanisms have emerged as promising therapeutic strategies for subarachnoid hemorrhage.This review provides an overview of recent research advances in mitochondrial pathophysiological processes after subarachnoid hemorrhage,particularly mitochondrial quality control mechanisms.It also presents potential therapeutic strategies to target mitochondrial quality control in subarachnoid hemorrhage.
基金supported by National Natural Science Foundation of China (No.11974301)Key Research and Development Program of Hunan Province (No.2022GK2007)+2 种基金Key Project from Department Education of Hunan Province (No.22A0123)Scientific Research Fund of Hunan Provincial Education Department (No.21B0136)National college students innovation and entrepreneurship training program (No.S202310530016)。
文摘Palladium(Pd)-based sulfides have triggered extensive interest due to their unique properties and potential applications in the fields of electronics and optoelectronics.However,the synthesis of large-scale uniform PdS and PdS_(2)nanofilms(NFs)remains an enormous challenge.In this work,2-inch wafer-scale PdS and PdS_(2) NFs with excellent stability can be controllably prepared via chemical vapor deposition combined with electron beam evaporation technique.The thickness of the pre-deposited Pd film and the sulfurization temperature are critical for the precise synthesis of PdS and PdS_(2) NFs.A corresponding growth mechanism has been proposed based on our experimental results and Gibbs free energy calculations.The electrical transport properties of PdS and PdS_(2) NFs were explored by conductive atomic force microscopy.Our findings have achieved the controllable growth of PdS and PdS_(2) NFs,which may provide a pathway to facilitate PdS and PdS_(2) based applications for next-generation high performance optoelectronic devices.
基金partially supported by National Natura Science Foundation of China (62350710214, U23A20325)Shenzhen Key Laboratory of Control Theory and Intelligent Systems (ZDSYS20220330161800001)。
文摘In this tutorial paper, we explore the field of quantized feedback control, which has gained significant attention due to the growing prevalence of networked control systems. These systems require the transmission of feedback information, such as measurements and control signals, over digital networks, presenting novel challenges in estimation and control design. Our examination encompasses various topics, including the minimal information needed for effective feedback control, the design of quantizers, strategies for quantized control design and estimation,achieving consensus control with quantized data, and the pursuit of high-precision tracking using quantized measurements.
基金supported by the National Natu-ral Science Foundation of China(No.11575187)the National Key Research and Development Program(No.2016YFB0700205).
文摘As a direct wide bandgap semiconductor,CsPbCl_(3)has great potential applications in the eld of near-ultraviolet photodetectors,lasers and higher-order multiphoton uores-cent detectors.In this work,we synthesized CsPbCl_(3)micro/nanocrystals by vapor depo-sition method with CsCl and PbCl_(2)powders as the source materials.It was con rmed that the formation of CsPbCl_(3)perovskite through the chemical reaction of CsCl with PbCl_(2)occurred in the quartz boat before the source evaporation,not in vapor or on sub-strate surface.The evaporated CsPbCl_(3)can form micro/nanocrystals on substrate surfaces under appropriate conditions.Various morphologies including irregular polyhedrons,rods and pyramids could be observed at lower temperature,while stable and uniform CsPbCl_(3)single crystal microplatelets were controllably synthesized at 450℃.Prolonging the growth time could modulate the size and density of the microcrystals,but could not change the morphology.Substrate types made little di erence to the morphology of CsPbCl_(3)crystals.The photoluminescence spectra indicated that the crystallinity and morphology of CsPbCl_(3)micro/nanocrystals have signi cant e ects on their optical properties.The work is expected to be helpful to the development of optoelectronic devices based on individual CsPbCl_(3)microcrystal.
基金Project supported by the Hunan Provincial Natural Science Foundation of China(Grant No.2021JJ30738)Scientific Research Fund of Hunan Provincial Education Department(Grant No.19K001)Hunan Provincial Key Laboratory of Flexible Electronic Materials Genome Engineering’s Open Fund Project-2020(Grant No.202016)。
文摘A novel 4H-Si C trench insulated gate bipolar transistor(IGBT)with a controllable hole-extracting(CHE)path is proposed and investigated in this paper.The CHE path is controlled by metal semiconductor gate(MES gate)and metal oxide semiconductor gate(MOS gate)in the p-shield region.The grounded p-shield region can significantly suppress the high electric field around gate oxide in Si C devices,but it weakens the conductivity modulation in the Si C trench IGBT by rapidly sweeping out holes.This effect can be eliminated by introducing the CHE path.The CHE path is pinched off by the high gate bias voltage at on-state to maintain high conductivity modulation and obtain a comparatively low on-state voltage(VON).During the turn-off transient,the CHE path is formed,which contributes to a decreased turn-off loss(EOFF).Based on numerical simulation,the EOFFof the proposed IGBT is reduced by 89%compared with the conventional IGBT at the same VONand the VONof the proposed IGBT is reduced by 50%compared to the grounded p-shield IGBT at the same EOFF.In addition,the average power reduction for the proposed device can be 51.0%to 81.7%and 58.2%to 72.1%with its counterparts at a wide frequency range of 500 Hz to 10 k Hz,revealing a great improvement of frequency characteristics.
基金the National Natural Science Foundation of China(62203356)Fundamental Research Funds for the Central Universities of China(31020210502002)。
文摘This paper studies the problem of time-varying formation control with finite-time prescribed performance for nonstrict feedback second-order multi-agent systems with unmeasured states and unknown nonlinearities.To eliminate nonlinearities,neural networks are applied to approximate the inherent dynamics of the system.In addition,due to the limitations of the actual working conditions,each follower agent can only obtain the locally measurable partial state information of the leader agent.To address this problem,a neural network state observer based on the leader state information is designed.Then,a finite-time prescribed performance adaptive output feedback control strategy is proposed by restricting the sliding mode surface to a prescribed region,which ensures that the closed-loop system has practical finite-time stability and that formation errors of the multi-agent systems converge to the prescribed performance bound in finite time.Finally,a numerical simulation is provided to demonstrate the practicality and effectiveness of the developed algorithm.
基金the Research Grants Council of Hong Kong(CityU 21208921)the Chow Sang Sang Group Research Fund Sponsored by Chow Sang Sang Holdings International Ltd.
文摘This paper proposes a novel event-driven encrypted control framework for linear networked control systems(NCSs),which relies on two modified uniform quantization policies,the Paillier cryptosystem,and an event-triggered strategy.Due to the fact that only integers can work in the Pailler cryptosystem,both the real-valued control gain and system state need to be first quantized before encryption.This is dramatically different from the existing quantized control methods,where only the quantization of a single value,e.g.,the control input or the system state,is considered.To handle this issue,static and dynamic quantization policies are presented,which achieve the desired integer conversions and guarantee asymptotic convergence of the quantized system state to the equilibrium.Then,the quantized system state is encrypted and sent to the controller when the triggering condition,specified by a state-based event-triggered strategy,is satisfied.By doing so,not only the security and confidentiality of data transmitted over the communication network are protected,but also the ciphertext expansion phenomenon can be relieved.Additionally,by tactfully designing the quantization sensitivities and triggering error,the proposed event-driven encrypted control framework ensures the asymptotic stability of the overall closedloop system.Finally,a simulation example of the secure motion control for an inverted pendulum cart system is presented to evaluate the effectiveness of the theoretical results.
基金supported by the National Natural Science Foundation of China (61991400, 61991403, 62273064, 62250710167,61860206008, 61933012, 62203078)in part by the National Key Research and Development Program of China (2022YFB4701400/4701401)+1 种基金the Innovation Support Program for International Students Returning to China(cx2022016)the CAAI-Huawei MindSpore Open Fund。
文摘This paper investigates the prescribed-time control(PTC) problem for a class of strict-feedback systems subject to non-vanishing uncertainties. The coexistence of mismatched uncertainties and non-vanishing disturbances makes PTC synthesis nontrivial. In this work, a control method that does not involve infinite time-varying gain is proposed, leading to a practical and global prescribed time tracking control solution for the strict-feedback systems, in spite of both the mismatched and nonvanishing uncertainties. Different from methods based on control switching to avoid the issue of infinite control gain that involves control discontinuity at the switching point, in our method a softening unit is exclusively included to ensure the continuity of the control action. Furthermore, in contrast to most existing prescribed-time control works where the control scheme is only valid on a finite time interval, in this work, the proposed control scheme is valid on the entire time interval. In addition, the prior information on the upper or lower bound of gi is not in need,enlarging the applicability of the proposed method. Both the theoretical analysis and numerical simulation confirm the effectiveness of the proposed control algorithm.
基金supported by the National Natural Science Foundation of China(U21A20166)in part by the Science and Technology Development Foundation of Jilin Province (20230508095RC)+1 种基金in part by the Development and Reform Commission Foundation of Jilin Province (2023C034-3)in part by the Exploration Foundation of State Key Laboratory of Automotive Simulation and Control。
文摘Aiming at the tracking problem of a class of discrete nonaffine nonlinear multi-input multi-output(MIMO) repetitive systems subjected to separable and nonseparable disturbances, a novel data-driven iterative learning control(ILC) scheme based on the zeroing neural networks(ZNNs) is proposed. First, the equivalent dynamic linearization data model is obtained by means of dynamic linearization technology, which exists theoretically in the iteration domain. Then, the iterative extended state observer(IESO) is developed to estimate the disturbance and the coupling between systems, and the decoupled dynamic linearization model is obtained for the purpose of controller synthesis. To solve the zero-seeking tracking problem with inherent tolerance of noise,an ILC based on noise-tolerant modified ZNN is proposed. The strict assumptions imposed on the initialization conditions of each iteration in the existing ILC methods can be absolutely removed with our method. In addition, theoretical analysis indicates that the modified ZNN can converge to the exact solution of the zero-seeking tracking problem. Finally, a generalized example and an application-oriented example are presented to verify the effectiveness and superiority of the proposed process.
基金partially supported by the Natural Science Foundation of China (Grant Nos.62103052,52272358)partially supported by the Beijing Institute of Technology Research Fund Program for Young Scholars。
文摘This paper investigates the adaptive trajectory tracking control problem and the unknown parameter identification problem of a class of rotor-missiles with parametric system uncertainties.First,considering the uncertainty of structural and aerodynamic parameters,the six-degree-of-freedom(6Do F) nonlinear equations describing the position and attitude dynamics of the rotor-missile are established,respectively,in the inertial and body-fixed reference frames.Next,a hierarchical adaptive trajectory tracking controller that can guarantee closed-loop stability is proposed according to the cascade characteristics of the 6Do F dynamics.Then,a memory-augmented update rule of unknown parameters is proposed by integrating all historical data of the regression matrix.As long as the finitely excited condition is satisfied,the precise identification of unknown parameters can be achieved.Finally,the validity of the proposed trajectory tracking controller and the parameter identification method is proved through Lyapunov stability theory and numerical simulations.
基金Project supported by the Natural Science Foundation of Shanxi Province of China (Grant No. 202203021221214)the National Natural Science Foundation of China (Grant Nos. 62122044, 62135008, 61925503, 11904218, 12004276, 12147215, and 11834010)+4 种基金the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi Province of China (Grant Nos. 2019L0092 and 2020L0029)the Key Project of the National Key Research and Development Program of China (Grant No. 2022YFA1404500)the Program for the Innovative Talents of Higher Education Institutions of Shanxi Province of Chinathe Program for the Outstanding Innovative Teams of Higher Learning Institutions of Shanxithe Fund for Shanxi “1331 Project” Key Subjects Construction
文摘A quantum teleportation network involving multiple users is essential for future quantum internet.So far,controlled quantum teleportation has been demonstrated in a three-user network.However,versatile and controlled quantum teleportation network involving more users is in demand,which satisfies different combinations of users for practical requirements.Here we propose a highly versatile and controlled teleportation network that can switch among various combinations of different users.We use a single continuous-variable six-partite Greenberger-Horne-Zeilinger(GHZ)state to realize such a task by choosing the different measurement and feedback operations.The controlled teleportation network,which includes one sub-network,two sub-networks and three sub-networks,can be realized for different application of user combinations.Furthermore,the coherent feedback control(CFC)can manipulate and improve the teleportation performance.Our approach is flexible and scalable,and would provide a versatile platform for demonstrations of complex quantum communication and quantum computing protocols.