In this paper,a stochastic multi-group AIDS model with saturated incidence rate is studied.We prove that the system is persistent in the mean under some parametric restrictions.We also obtain the sufficient condition ...In this paper,a stochastic multi-group AIDS model with saturated incidence rate is studied.We prove that the system is persistent in the mean under some parametric restrictions.We also obtain the sufficient condition for the existence of the ergodic stationary distribution of the system by constructing a suitable Lyapunov function.Our results indicate that the existence of ergodic stationary distribution does not rely on the interior equilibrium of the corresponding deterministic system,which greatly improves upon previous results.展开更多
This paper studies stratified magnetohydrodynamic （MHD） flow of tan- gent hyperbolic nanofluid past an inclined exponentially stretching surface. The flow is subjected to velocity, thermal, and solutal boundary cond...This paper studies stratified magnetohydrodynamic （MHD） flow of tan- gent hyperbolic nanofluid past an inclined exponentially stretching surface. The flow is subjected to velocity, thermal, and solutal boundary conditions. The partial differential systems are reduced to ordinary differential systems using appropriate transformations. The reduced systems are solved for convergent series solutions. The velocity, temperature, and concentration fields are discussed for different physical parameters. The results indi- cate that the temperature and the thermal boundary layer thickness increase noticeably for large values of Brownian motion and thermophoresis effects. It is also observed that the buoyancy parameter strengthens the velocity field, showing a decreasing behavior of temperature and nanoparticle volume fraction profiles.展开更多
Fabrication of reusable adsorbents with satisfactory adsorption capacity and using environmentfriendly preparation processes is required for the environment-related applications. In this study,acrylic acid（AA） was g...Fabrication of reusable adsorbents with satisfactory adsorption capacity and using environmentfriendly preparation processes is required for the environment-related applications. In this study,acrylic acid（AA） was grafted onto bentonite（BT） to generate an AA-graft-BT（AA-g-BT）composite using a plasma-induced grafting technique considered to be an environment-friendly method. The as-prepared composite was characterized by scanning electron microscopy, x-ray powder diffraction, thermal gravity analysis, Fourier transform infrared spectroscopy and Barrett–Emmett–Teller analysis, demonstrating the successful grafting of AA onto BT. In addition, the removal of uranium（VI）（U（VI）） from contaminated aqueous solutions was examined using the as-prepared composite. The influencing factors, including contact time,p H value, ionic strength, temperature, and initial concentration, for the removal of U（VI） were investigated by batch experiments. The experimental process fitted best with the pseudo-secondorder kinetic and the Langmuir models. Moreover, thermodynamic investigation revealed a spontaneous and endothermic process. Compared with previous adsorbents, AA-g-BT has potential practical applications in treating U（VI）-contaminated solutions.展开更多
The decoherence of entangled states caused by the noisy channel is a salient problem for reducing the fidelity of quantum communication.Here we present a heralded two-photon entanglement purification protocol(EPP)usin...The decoherence of entangled states caused by the noisy channel is a salient problem for reducing the fidelity of quantum communication.Here we present a heralded two-photon entanglement purification protocol(EPP)using heralded high-fidelity parity-check gate(HH-PCG),which can increase the entanglement of nonlocal two-photon polarization mixed state.The HH-PCG is constructed by the input-output process of nitrogen-vacancy(NV)center in diamond embedded in a single-sided optical cavity,where the errors caused by the imperfect interaction between the NV center-cavity system and the photon can be heralded by the photon detector.As the unwanted components can be filtrated due to the heralded function,the fidelity of the EPP scheme can be enhanced considerably,which will increase the fidelity of quantum communication processing.展开更多
Synchronization rhythm and oscillating in biological systems can give clues to understanding the cooperation and competition between cells under appropriate biological and physical conditions. As a result, the network...Synchronization rhythm and oscillating in biological systems can give clues to understanding the cooperation and competition between cells under appropriate biological and physical conditions. As a result, the network setting is appreciated to detect the stability and transition of collective behaviors in a network with different connection types. In this paper, the synchronization performance in time-delayed excitable homogeneous random networks（EHRNs） induced by diversity in system parameters is investigated by calculating the synchronization parameter and plotting the spatiotemporal evolution pattern, and distinct impacts induced by parameter-diversity are detected by setting different time delays. It is found that diversity has no distinct effect on the synchronization performance in EHRNs with small time delay being considered. When time delay is increased greatly, the synchronization performance of EHRN degenerates remarkably as diversity is increased. Surprisingly, by setting a moderate time delay, appropriate parameter-diversity can promote the synchronization performance in EHRNs, and can induce the synchronization transition from the asynchronous state to the weak synchronization. Moreover, the bistability phenomenon, which contains the states of asynchronous state and weak synchronization,is observed. Particularly, it is confirmed that the parameter-diversity promoted synchronization performance in time-delayed EHRN is manifested in the enhancement of the synchronization performance of individual oscillation and the increase of the number of synchronization transitions from the asynchronous state to the weak synchronization. Finally, we have revealed that this kind of parameter-diversity promoted synchronization performance is a robust phenomenon.展开更多
Electric and chemical synapse play important role in connecting neurons and thus signal propagation can be realized between neurons. External electric stimulus can change the excitability of neuron and then the electr...Electric and chemical synapse play important role in connecting neurons and thus signal propagation can be realized between neurons. External electric stimulus can change the excitability of neuron and then the electrical activities can be modulated completely. Continuous fluctuation of ion concentration in cell can induce complex time-varying electromagnetic field during the exchange of charged ions across the membrane of neuron. Polarization and magnetization in the media(and neuron), which exposed to electromagnetic radiation, can modulate the dynamical response and mode transition in electrical activities of neurons. In this paper, magnetic flux is used to describe the effect of electromagnetic field, and the three-variable HindmarshRose neuron model is updated to propose a four-variable neuron model that the effect of electromagnetic induction and radiation can be explained. Based on the physical law of electromagnetic induction, exchange of charged ions and flow of ion currents will change the distribution of electromagnetic filed in cell, and each neuron will be exposed to the superimposed field triggered by other neurons. Therefore, signal exchange could occur even synapse coupling between neurons is removed in the case of field coupling. A chain network is proposed to investigate the signal exchange between neurons under field coupling when synapse coupling is not available. It is found that field coupling between neurons can change the collective behaviors in electrical activities. A statistical factor of synchronization and spatial patterns are calculated, these results confirmed that field coupling is effective for signal communication between neurons. In the end, open problems are suggested for readers' extensive guidance in this field.展开更多
Nonlinear oscillators and circuits can be coupled to reach synchronization and consensus. The occurrence of complete synchronization means that all oscillators can maintain the same amplitude and phase, and it is ofte...Nonlinear oscillators and circuits can be coupled to reach synchronization and consensus. The occurrence of complete synchronization means that all oscillators can maintain the same amplitude and phase, and it is often detected between identical oscillators. However, phase synchronization means that the coupled oscillators just keep pace in oscillation even though the amplitude of each node could be different. For dimensionless dynamical systems and oscillators, the synchronization approach depends a great deal on the selection of coupling variable and type. For nonlinear circuits, a resistor is often used to bridge the connection between two or more circuits, so voltage coupling can be activated to generate feedback on the coupled circuits. In this paper, capacitor coupling is applied between two Pikovsk-Rabinovich(PR) circuits, and electric field coupling explains the potential mechanism for differential coupling. Then symmetric coupling and cross coupling are activated to detect synchronization stability, separately. It is found that resistor-based voltage coupling via a single variable can stabilize the synchronization, and the energy flow of the controller is decreased when synchronization is realized. Furthermore, by applying appropriate intensity for the coupling capacitor, synchronization is also reached and the energy flow across the coupling capacitor is helpful in regulating the dynamical behaviors of coupled circuits, which are supported by a continuous energy exchange between capacitors and the inductor. It is also confirmed that the realization of synchronization is dependent on the selection of a coupling channel. The approach and stability of complete synchronization depend on symmetric coupling, which is activated between the same variables. Cross coupling between different variables just triggers phase synchronization. The capacitor coupling can avoid energy consumption for the case with resistor coupling, and it can also enhance the energy exchange between two coupled circuits.展开更多
There is a remarkable characteristic of photosynthesis in nature, that is, the energy transfer efficiency is close to 100%. Recently, due to the rapid progress made in the experimental techniques, quantum coherent eff...There is a remarkable characteristic of photosynthesis in nature, that is, the energy transfer efficiency is close to 100%. Recently, due to the rapid progress made in the experimental techniques, quantum coherent effects have been experimentally demonstrated. Traditionally, the incoherent theories are capable of calculating the energy transfer efficiency, e.g.,(generalized) F?rster theory and modified Redfield theory(MRT). However, in order to describe the quantum coherent effects in photosynthesis, one has to exploit coherent theories, such as hierarchical equation of motion(HEOM), quantum path integral, coherent modified Redfield theory(CMRT), small-polaron quantum master equation, and general Bloch-Redfield theory in addition to the Redfield theory. Here, we summarize the main points of the above approaches,which might be beneficial to the quantum simulation of quantum dynamics of exciton energy transfer(EET) in natural photosynthesis, and shed light on the design of artificial light-harvesting devices.展开更多
Static charges can induce spatial electric field while moving charges can induce magnetic field.As a result,continuous pumping and exchange of intercellular and extracellular Calcium,potassium and sodium of cells will...Static charges can induce spatial electric field while moving charges can induce magnetic field.As a result,continuous pumping and exchange of intercellular and extracellular Calcium,potassium and sodium of cells will generate time-varying magnetic field in the media.Therefore,the physical effect of electromagnetic induction in neural activities should be included in building biological neurons.On the other hand,the occurrence of action potential and propagation of ions require energy consumption and supply,so the estimation of physical energy becomes important.Based on our memristive biophysical neuron model,the Hamilton energy function is obtained by using the Helmholtz’s theorem,and this energy is contributed by the electric field and magnetic field described by magnetic flux.It is found that this improved neuron model can present the main dynamical properties in neural activities,and it characterizes the lower threshold behavior and subthreshold oscillation during refractory period.The external forcing current on an isolate is adjusted to calculate the firing patterns,energy function and mode transition,which shows the dependence of energy on electrical activities.Finally,magnetic coupling is triggered to modulate the phase synchronization between two identical neurons connected by electric synapse,respectively.展开更多
Biological neurons can receive inputs and capture a variety of external stimuli,which can be encoded and transmitted as different electric signals.Thus,the membrane potential is adjusted to activate the appropriate fi...Biological neurons can receive inputs and capture a variety of external stimuli,which can be encoded and transmitted as different electric signals.Thus,the membrane potential is adjusted to activate the appropriate firing modes.Indeed,reliable neuron models should take intrinsic biophysical effects and functional encoding into consideration.One fascinating and important question is the physical mechanism for the transcription of external signals.External signals can be transmitted as a transmembrane current or a signal voltage for generating action potentials.We present a photosensitive neuron model to estimate the nonlinear encoding and responses of neurons driven by external optical signals.In the model,a photocell(phototube)is used to activate a simple FitzHugh-Nagumo(FHN)neuron,and then external optical signals(illumination)are imposed to excite the photocell for generating a time-varying current/voltage source.The photocell-coupled FHN neuron can therefore capture and encode external optical signals,similar to artificial eyes.We also present detailed bifurcation analysis for estimating the mode transition and firing pattern selection of neuronal electrical activities.The sampled time series can reproduce the main characteristics of biological neurons(quiescent,spiking,bursting,and even chaotic behaviors)by activating the photocell in the neural circuit.These results could be helpful in giving possible guidance for studying neurodynamics and applying neural circuits to detect optical signals.展开更多
The two-dimensional（2D） perovskite（including pure-2D and quasi-2D） is formed by introducing large-group ammonium halides into conventional bulk perovskite. In the past twenty years, 2D perovskite materials were wi...The two-dimensional（2D） perovskite（including pure-2D and quasi-2D） is formed by introducing large-group ammonium halides into conventional bulk perovskite. In the past twenty years, 2D perovskite materials were widely developed with the enriched species and advanced physicalknowledge in material characteristics as well as optoelectronic device applications. To review achievments in 2D perovskite,the fundamental mechanism and properties of 2D perovskite are introduced to offer insight into device performance.Moreover, the preparation methods of 2D perovskite films are summarized and compared. The latest successful applications of the 2D perovskite in the solar cells and light-emitting diodes fields, especially the advanced stability of 2D perovskite solar cells（PeSCs） and the efficient 2D perovskite lightemitting diodes（PeLEDs）, are also achieved. Furthermore, the challenges and outlook of 2D perovskite materials are proposed.展开更多
Hyperentanglement has attracted considerable attention recently because of its high-capacity for long- distance quantum communication. In this study, we present a hyperentanglement concentration pro- tocol （hyper-ECP...Hyperentanglement has attracted considerable attention recently because of its high-capacity for long- distance quantum communication. In this study, we present a hyperentanglement concentration pro- tocol （hyper-ECP） for nonlocal three-photon systems in the polarization, spatial-mode, and time- bin partially hyperentangled Greenberger-Horne-Zeilinger （GHZ） states using the Schmidt projection method. In our hyper-ECP, the three distant parties must perform the parity-check measurements on the polarization, spatial-mode, and time-bin degrees of freedom, respectively, using linear optical ele- ments and Pockels cells, and only two identical nonlocal photon systems are required. This hyper-ECP can be directly extended to the N-photon hyperentangled GHZ states, and the success probability of this general hyper-ECP for a nonlocal N-photon system is the optimal one, regardless of the photon number N.展开更多
Perovskite solar cells(PSCs) have drawn wide attention due to the rapidly rising efficiency which presently attains over 23%. However, problems of instability continue to plague the high-efficiency devices impairing t...Perovskite solar cells(PSCs) have drawn wide attention due to the rapidly rising efficiency which presently attains over 23%. However, problems of instability continue to plague the high-efficiency devices impairing their practical applications. Here, by firstly introducing smaller-size NH4+ into(FAPbI3)0.85(MAPbBr3)0.15(FA/MA) to form a novel 2D-3D mixed structure, we designed and prepared new-type hybrid perovskite materials of [(NH4)2.4(FA)n-1PbnI3n+1.4]0.85(MAPbBr3)0.15(n=3, 5, 7, 9 and 11)(A/FA/MA) and used them as absorber in solar cells. Especially, unlike the reported 2D/MD perovskite perovskites based on larger-size ammonium salts;A/FA/MA perovskites are the first to display red-shift light absorption and decreased band gaps in comparison to normal perovskites. Consequently, when n=9, the A/FA/MA device shows outstanding performance with a solar to electric power conversion efficiency(PCE) of 18.25% and negligible hysteresis. When the encapsulated A/FA/MA perovskite device was soaked in full sunlight for 1,000 h, the PCE remains almost unchanged. Moreover, the unsealed A/FA/MA PSCs maintain 90% of their initial PCE when aged at high humidity conditions over the same 1000-h time period. Our findings provide a guide for the future development of such novel perovskites and it is helpful to select more suitable ammonium salt to obtain highly efficient and stable 2D-3D PSCs.展开更多
Quantum state transmission is a prerequisite for various quantum communication networks. The channel noise inevitably introduces distortion of quantum states passing through either a free-space channel or a fibre chan...Quantum state transmission is a prerequisite for various quantum communication networks. The channel noise inevitably introduces distortion of quantum states passing through either a free-space channel or a fibre channel, which leads to errors or decreases the security of a practical quantum communication network. Quantum error rejection is a useful technology to faithfully transmit quantum states over large-scale quantum channels. It provides the communication parties with an uncorrupted quantum state by rejecting error states. Usually, additional photons or degrees of freedom are required to overcome the adverse effects of channel noise. As quantum error rejection method consumes less quantum resource than other anti-noise methods, it is more convenient to perform error-rejection quantum state transmission with current technology. In this review, several typical quantum errorrejection schemes for single-photon state transmission are introduced in brief and some error-rejection schemes for entanglement distribution are also briefly presented.展开更多
It has been revealed experimentally that astrocytes can participate in synaptic transmission by modulating and responding to the release of neurotransmitters with calcium elevations. Researches suggest that seizure-li...It has been revealed experimentally that astrocytes can participate in synaptic transmission by modulating and responding to the release of neurotransmitters with calcium elevations. Researches suggest that seizure-like discharges(SDs) or seizure-like firings(SFs) in neurons, characterizing neurological disorder, may arise locally in restricted areas(focal area) and then propagate throughout the brain. But the underlying mechanism remains unclear. To study the possible role astrocytes playing in the SDs propagation, we construct a minimal neuron-astrocyte network model by connecting a neurons chain and an astrocytes chain.The focal area is modelled by an IP3 reservoir which provides persistent IP3 out-flux. The study suggests that calcium wave propagation in astrocytes determines the propagation of SDs in the connected neurons. On the other hand, SDs in neurons allows the calcium wave propagates longer distance in the astrocytes, which suggests the mutually cooperating of astrocytes and neurons in accomplishing SD propagation. Furthermore, once SDs propagate and occupy the neuron network, it could not be terminated by recovery of the focal area. The results may imply that treatment of brain disorders should not only focus on local area but the whole neuron network.展开更多
We theoretically investigate the intra-band transitions in Mobius molecules.Due to the weak magnetic response,the relative permittivity is significantly modified by the presence of the medium while the relative permea...We theoretically investigate the intra-band transitions in Mobius molecules.Due to the weak magnetic response,the relative permittivity is significantly modified by the presence of the medium while the relative permeability is not.We show that there is hyperbolic dispersion relation induced by the intra-band transitions because one of the eigen-values of permittivity possesses a different sign from the other two,while all three eigen-values of permeability are positive.We further demonstrate that the bandwidth of negative refraction is 0.165 eV for the H-polarized incident light,which is broader than the ones for inter-band transitions by 3 orders of magnitude.Moreover,the frequency domain has been shifted from ultra-violet to visible domain.Although there is negative refraction for the E-polarized incident light,the bandwidth is much narrower and depends on the incident angle.展开更多
基金The work was supported by NSF of China(11801041,11871473)Foudation of Jilin Province Science and Technology Development(20190201130JC)+1 种基金Scientific Rsearch Foundation of Jilin Provincial Education Department(JJKH20181172KJ,JJKH20190503KJ)Natural Science Foundation of Changchun Normal University.
文摘In this paper,a stochastic multi-group AIDS model with saturated incidence rate is studied.We prove that the system is persistent in the mean under some parametric restrictions.We also obtain the sufficient condition for the existence of the ergodic stationary distribution of the system by constructing a suitable Lyapunov function.Our results indicate that the existence of ergodic stationary distribution does not rely on the interior equilibrium of the corresponding deterministic system,which greatly improves upon previous results.
文摘This paper studies stratified magnetohydrodynamic （MHD） flow of tan- gent hyperbolic nanofluid past an inclined exponentially stretching surface. The flow is subjected to velocity, thermal, and solutal boundary conditions. The partial differential systems are reduced to ordinary differential systems using appropriate transformations. The reduced systems are solved for convergent series solutions. The velocity, temperature, and concentration fields are discussed for different physical parameters. The results indi- cate that the temperature and the thermal boundary layer thickness increase noticeably for large values of Brownian motion and thermophoresis effects. It is also observed that the buoyancy parameter strengthens the velocity field, showing a decreasing behavior of temperature and nanoparticle volume fraction profiles.
基金the Special Scientific Fund of Public Welfare Profession of China (No. 201509074)National Natural Science Foundation of China (Nos. 21272236, U1230202)
文摘Fabrication of reusable adsorbents with satisfactory adsorption capacity and using environmentfriendly preparation processes is required for the environment-related applications. In this study,acrylic acid（AA） was grafted onto bentonite（BT） to generate an AA-graft-BT（AA-g-BT）composite using a plasma-induced grafting technique considered to be an environment-friendly method. The as-prepared composite was characterized by scanning electron microscopy, x-ray powder diffraction, thermal gravity analysis, Fourier transform infrared spectroscopy and Barrett–Emmett–Teller analysis, demonstrating the successful grafting of AA onto BT. In addition, the removal of uranium（VI）（U（VI）） from contaminated aqueous solutions was examined using the as-prepared composite. The influencing factors, including contact time,p H value, ionic strength, temperature, and initial concentration, for the removal of U（VI） were investigated by batch experiments. The experimental process fitted best with the pseudo-secondorder kinetic and the Langmuir models. Moreover, thermodynamic investigation revealed a spontaneous and endothermic process. Compared with previous adsorbents, AA-g-BT has potential practical applications in treating U（VI）-contaminated solutions.
基金Project supported by the National Natural Science Foundation of China(Grants Nos.11674033,11474026,11604226,and 11475021)Science and Technology Program Foundation of the Beijing Municipal Commission of Education of China(Grant Nos.KM201710028005 and CIT&TCD201904080)
文摘The decoherence of entangled states caused by the noisy channel is a salient problem for reducing the fidelity of quantum communication.Here we present a heralded two-photon entanglement purification protocol(EPP)using heralded high-fidelity parity-check gate(HH-PCG),which can increase the entanglement of nonlocal two-photon polarization mixed state.The HH-PCG is constructed by the input-output process of nitrogen-vacancy(NV)center in diamond embedded in a single-sided optical cavity,where the errors caused by the imperfect interaction between the NV center-cavity system and the photon can be heralded by the photon detector.As the unwanted components can be filtrated due to the heralded function,the fidelity of the EPP scheme can be enhanced considerably,which will increase the fidelity of quantum communication processing.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11675001,11675112,11775020,and 11372122)
文摘Synchronization rhythm and oscillating in biological systems can give clues to understanding the cooperation and competition between cells under appropriate biological and physical conditions. As a result, the network setting is appreciated to detect the stability and transition of collective behaviors in a network with different connection types. In this paper, the synchronization performance in time-delayed excitable homogeneous random networks（EHRNs） induced by diversity in system parameters is investigated by calculating the synchronization parameter and plotting the spatiotemporal evolution pattern, and distinct impacts induced by parameter-diversity are detected by setting different time delays. It is found that diversity has no distinct effect on the synchronization performance in EHRNs with small time delay being considered. When time delay is increased greatly, the synchronization performance of EHRN degenerates remarkably as diversity is increased. Surprisingly, by setting a moderate time delay, appropriate parameter-diversity can promote the synchronization performance in EHRNs, and can induce the synchronization transition from the asynchronous state to the weak synchronization. Moreover, the bistability phenomenon, which contains the states of asynchronous state and weak synchronization,is observed. Particularly, it is confirmed that the parameter-diversity promoted synchronization performance in time-delayed EHRN is manifested in the enhancement of the synchronization performance of individual oscillation and the increase of the number of synchronization transitions from the asynchronous state to the weak synchronization. Finally, we have revealed that this kind of parameter-diversity promoted synchronization performance is a robust phenomenon.
基金supported by the National Natural Science Foundation of China(Grant Nos.11672122&11765011)
文摘Electric and chemical synapse play important role in connecting neurons and thus signal propagation can be realized between neurons. External electric stimulus can change the excitability of neuron and then the electrical activities can be modulated completely. Continuous fluctuation of ion concentration in cell can induce complex time-varying electromagnetic field during the exchange of charged ions across the membrane of neuron. Polarization and magnetization in the media(and neuron), which exposed to electromagnetic radiation, can modulate the dynamical response and mode transition in electrical activities of neurons. In this paper, magnetic flux is used to describe the effect of electromagnetic field, and the three-variable HindmarshRose neuron model is updated to propose a four-variable neuron model that the effect of electromagnetic induction and radiation can be explained. Based on the physical law of electromagnetic induction, exchange of charged ions and flow of ion currents will change the distribution of electromagnetic filed in cell, and each neuron will be exposed to the superimposed field triggered by other neurons. Therefore, signal exchange could occur even synapse coupling between neurons is removed in the case of field coupling. A chain network is proposed to investigate the signal exchange between neurons under field coupling when synapse coupling is not available. It is found that field coupling between neurons can change the collective behaviors in electrical activities. A statistical factor of synchronization and spatial patterns are calculated, these results confirmed that field coupling is effective for signal communication between neurons. In the end, open problems are suggested for readers' extensive guidance in this field.
基金Project supported by the National Natural Science Foundation of China(No.11672122)
文摘Nonlinear oscillators and circuits can be coupled to reach synchronization and consensus. The occurrence of complete synchronization means that all oscillators can maintain the same amplitude and phase, and it is often detected between identical oscillators. However, phase synchronization means that the coupled oscillators just keep pace in oscillation even though the amplitude of each node could be different. For dimensionless dynamical systems and oscillators, the synchronization approach depends a great deal on the selection of coupling variable and type. For nonlinear circuits, a resistor is often used to bridge the connection between two or more circuits, so voltage coupling can be activated to generate feedback on the coupled circuits. In this paper, capacitor coupling is applied between two Pikovsk-Rabinovich(PR) circuits, and electric field coupling explains the potential mechanism for differential coupling. Then symmetric coupling and cross coupling are activated to detect synchronization stability, separately. It is found that resistor-based voltage coupling via a single variable can stabilize the synchronization, and the energy flow of the controller is decreased when synchronization is realized. Furthermore, by applying appropriate intensity for the coupling capacitor, synchronization is also reached and the energy flow across the coupling capacitor is helpful in regulating the dynamical behaviors of coupled circuits, which are supported by a continuous energy exchange between capacitors and the inductor. It is also confirmed that the realization of synchronization is dependent on the selection of a coupling channel. The approach and stability of complete synchronization depend on symmetric coupling, which is activated between the same variables. Cross coupling between different variables just triggers phase synchronization. The capacitor coupling can avoid energy consumption for the case with resistor coupling, and it can also enhance the energy exchange between two coupled circuits.
基金supported by the National Basic Research Program of China (2017YFA0303704)the National Natural Science Foundation of China (61727801, 11774197, 11474181, 11674033, 11505007 and 11474026).
文摘There is a remarkable characteristic of photosynthesis in nature, that is, the energy transfer efficiency is close to 100%. Recently, due to the rapid progress made in the experimental techniques, quantum coherent effects have been experimentally demonstrated. Traditionally, the incoherent theories are capable of calculating the energy transfer efficiency, e.g.,(generalized) F?rster theory and modified Redfield theory(MRT). However, in order to describe the quantum coherent effects in photosynthesis, one has to exploit coherent theories, such as hierarchical equation of motion(HEOM), quantum path integral, coherent modified Redfield theory(CMRT), small-polaron quantum master equation, and general Bloch-Redfield theory in addition to the Redfield theory. Here, we summarize the main points of the above approaches,which might be beneficial to the quantum simulation of quantum dynamics of exciton energy transfer(EET) in natural photosynthesis, and shed light on the design of artificial light-harvesting devices.
基金supported partially by the National Natural Science Foundation of China(Grant No.11672122)。
文摘Static charges can induce spatial electric field while moving charges can induce magnetic field.As a result,continuous pumping and exchange of intercellular and extracellular Calcium,potassium and sodium of cells will generate time-varying magnetic field in the media.Therefore,the physical effect of electromagnetic induction in neural activities should be included in building biological neurons.On the other hand,the occurrence of action potential and propagation of ions require energy consumption and supply,so the estimation of physical energy becomes important.Based on our memristive biophysical neuron model,the Hamilton energy function is obtained by using the Helmholtz’s theorem,and this energy is contributed by the electric field and magnetic field described by magnetic flux.It is found that this improved neuron model can present the main dynamical properties in neural activities,and it characterizes the lower threshold behavior and subthreshold oscillation during refractory period.The external forcing current on an isolate is adjusted to calculate the firing patterns,energy function and mode transition,which shows the dependence of energy on electrical activities.Finally,magnetic coupling is triggered to modulate the phase synchronization between two identical neurons connected by electric synapse,respectively.
基金Project supported by the National Natural Science Foundation of China(No.11672122)the Hongliu First-Class Disciplines Development Program of Lanzhou University of Technology,China。
文摘Biological neurons can receive inputs and capture a variety of external stimuli,which can be encoded and transmitted as different electric signals.Thus,the membrane potential is adjusted to activate the appropriate firing modes.Indeed,reliable neuron models should take intrinsic biophysical effects and functional encoding into consideration.One fascinating and important question is the physical mechanism for the transcription of external signals.External signals can be transmitted as a transmembrane current or a signal voltage for generating action potentials.We present a photosensitive neuron model to estimate the nonlinear encoding and responses of neurons driven by external optical signals.In the model,a photocell(phototube)is used to activate a simple FitzHugh-Nagumo(FHN)neuron,and then external optical signals(illumination)are imposed to excite the photocell for generating a time-varying current/voltage source.The photocell-coupled FHN neuron can therefore capture and encode external optical signals,similar to artificial eyes.We also present detailed bifurcation analysis for estimating the mode transition and firing pattern selection of neuronal electrical activities.The sampled time series can reproduce the main characteristics of biological neurons(quiescent,spiking,bursting,and even chaotic behaviors)by activating the photocell in the neural circuit.These results could be helpful in giving possible guidance for studying neurodynamics and applying neural circuits to detect optical signals.
基金supported by the National Key Research and Development Program of China (2016YFA0202401)the 111 Project (B16016)+1 种基金the National Natural Science Foundation of China (51572080, 51702096 and U1705256)the Fundamental Research Funds for the Central Universities (2017XS080)
文摘The two-dimensional（2D） perovskite（including pure-2D and quasi-2D） is formed by introducing large-group ammonium halides into conventional bulk perovskite. In the past twenty years, 2D perovskite materials were widely developed with the enriched species and advanced physicalknowledge in material characteristics as well as optoelectronic device applications. To review achievments in 2D perovskite,the fundamental mechanism and properties of 2D perovskite are introduced to offer insight into device performance.Moreover, the preparation methods of 2D perovskite films are summarized and compared. The latest successful applications of the 2D perovskite in the solar cells and light-emitting diodes fields, especially the advanced stability of 2D perovskite solar cells（PeSCs） and the efficient 2D perovskite lightemitting diodes（PeLEDs）, are also achieved. Furthermore, the challenges and outlook of 2D perovskite materials are proposed.
基金This work was supported by the National Natural Science Foundation of China under Grants Nos. 11604226, 11674033, and 11474026, and the Science and Technology Program Foundation of the Beijing Municipal Commission of Education of China under Grant No. KM201710028005.
文摘Hyperentanglement has attracted considerable attention recently because of its high-capacity for long- distance quantum communication. In this study, we present a hyperentanglement concentration pro- tocol （hyper-ECP） for nonlocal three-photon systems in the polarization, spatial-mode, and time- bin partially hyperentangled Greenberger-Horne-Zeilinger （GHZ） states using the Schmidt projection method. In our hyper-ECP, the three distant parties must perform the parity-check measurements on the polarization, spatial-mode, and time-bin degrees of freedom, respectively, using linear optical ele- ments and Pockels cells, and only two identical nonlocal photon systems are required. This hyper-ECP can be directly extended to the N-photon hyperentangled GHZ states, and the success probability of this general hyper-ECP for a nonlocal N-photon system is the optimal one, regardless of the photon number N.
基金financially supported by the National Key Research and Development Program of China (2016YFA0202401)the National Natural Science Foundation of China (51572080)
文摘Perovskite solar cells(PSCs) have drawn wide attention due to the rapidly rising efficiency which presently attains over 23%. However, problems of instability continue to plague the high-efficiency devices impairing their practical applications. Here, by firstly introducing smaller-size NH4+ into(FAPbI3)0.85(MAPbBr3)0.15(FA/MA) to form a novel 2D-3D mixed structure, we designed and prepared new-type hybrid perovskite materials of [(NH4)2.4(FA)n-1PbnI3n+1.4]0.85(MAPbBr3)0.15(n=3, 5, 7, 9 and 11)(A/FA/MA) and used them as absorber in solar cells. Especially, unlike the reported 2D/MD perovskite perovskites based on larger-size ammonium salts;A/FA/MA perovskites are the first to display red-shift light absorption and decreased band gaps in comparison to normal perovskites. Consequently, when n=9, the A/FA/MA device shows outstanding performance with a solar to electric power conversion efficiency(PCE) of 18.25% and negligible hysteresis. When the encapsulated A/FA/MA perovskite device was soaked in full sunlight for 1,000 h, the PCE remains almost unchanged. Moreover, the unsealed A/FA/MA PSCs maintain 90% of their initial PCE when aged at high humidity conditions over the same 1000-h time period. Our findings provide a guide for the future development of such novel perovskites and it is helpful to select more suitable ammonium salt to obtain highly efficient and stable 2D-3D PSCs.
基金supported by the National Natural Science Foundation of China(Grant Nos.11674033,and 11474026)the Natural Science Foundation of Jiangsu Province(Grant No.BK20180461)
文摘Quantum state transmission is a prerequisite for various quantum communication networks. The channel noise inevitably introduces distortion of quantum states passing through either a free-space channel or a fibre channel, which leads to errors or decreases the security of a practical quantum communication network. Quantum error rejection is a useful technology to faithfully transmit quantum states over large-scale quantum channels. It provides the communication parties with an uncorrupted quantum state by rejecting error states. Usually, additional photons or degrees of freedom are required to overcome the adverse effects of channel noise. As quantum error rejection method consumes less quantum resource than other anti-noise methods, it is more convenient to perform error-rejection quantum state transmission with current technology. In this review, several typical quantum errorrejection schemes for single-photon state transmission are introduced in brief and some error-rejection schemes for entanglement distribution are also briefly presented.
基金supported by the Fundamental Research Funds for the Central Universities of China(Grant No.2014QNA64(J.T.))
文摘It has been revealed experimentally that astrocytes can participate in synaptic transmission by modulating and responding to the release of neurotransmitters with calcium elevations. Researches suggest that seizure-like discharges(SDs) or seizure-like firings(SFs) in neurons, characterizing neurological disorder, may arise locally in restricted areas(focal area) and then propagate throughout the brain. But the underlying mechanism remains unclear. To study the possible role astrocytes playing in the SDs propagation, we construct a minimal neuron-astrocyte network model by connecting a neurons chain and an astrocytes chain.The focal area is modelled by an IP3 reservoir which provides persistent IP3 out-flux. The study suggests that calcium wave propagation in astrocytes determines the propagation of SDs in the connected neurons. On the other hand, SDs in neurons allows the calcium wave propagates longer distance in the astrocytes, which suggests the mutually cooperating of astrocytes and neurons in accomplishing SD propagation. Furthermore, once SDs propagate and occupy the neuron network, it could not be terminated by recovery of the focal area. The results may imply that treatment of brain disorders should not only focus on local area but the whole neuron network.
基金supported by the National Natural Science Foundation of China(Grant Nos.11505007,11674033,and 11474026).
文摘We theoretically investigate the intra-band transitions in Mobius molecules.Due to the weak magnetic response,the relative permittivity is significantly modified by the presence of the medium while the relative permeability is not.We show that there is hyperbolic dispersion relation induced by the intra-band transitions because one of the eigen-values of permittivity possesses a different sign from the other two,while all three eigen-values of permeability are positive.We further demonstrate that the bandwidth of negative refraction is 0.165 eV for the H-polarized incident light,which is broader than the ones for inter-band transitions by 3 orders of magnitude.Moreover,the frequency domain has been shifted from ultra-violet to visible domain.Although there is negative refraction for the E-polarized incident light,the bandwidth is much narrower and depends on the incident angle.
