This paper puts forward a high-speed train bogie active stability method,based on frame lateral vibration control,for improving the stability and critical speed of railway vehicles at high speeds.Two inertial actuator...This paper puts forward a high-speed train bogie active stability method,based on frame lateral vibration control,for improving the stability and critical speed of railway vehicles at high speeds.Two inertial actuators apply active control forces to the front and rear end beams of the bogie frame.A scale model of bogie lateral dynamics is established,as well as the state space equation of the control system.Also,the multi-objective optimization is used to construct state feedback parameters,which take hunting stability and control effort into account.Furthermore,the effects of time-delay in the control system and suspension parameters on bogie hunting stability are studied.The dynamic behaviors and the stability mechanism of the bogie control system are analyzed.Finally,a 1:5 scale test rig is used to conduct a bogie active stability experiment.The results reveal that active control of frame lateral vibration can effectively improve the bogie system's hunting stability margin at high speeds,but time-delay in the control system cannot be ignored.展开更多
The effect of oxygen partial pressure (Po2) during the channel layer deposition on bias stability of amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFTs) is investigated. As Po2 increases fr...The effect of oxygen partial pressure (Po2) during the channel layer deposition on bias stability of amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFTs) is investigated. As Po2 increases from 10% to 30%, it is found that the device shows enhanced bias stress stability with significantly reduced threshold voltage drift under positive gate bias stress. Based on the x-ray photoelectron spectroscopy measurement, the concentration of oxygen vacancies (Or) within the a-IGZO layer is suppressed by increasing Po2. Meanwhile, the low-frequency noise analysis indicates that the average trap density near the channel/dielectric interface continuously drops with increasing Po2. Therefore, the improved interface quality with increasing Po2 during the channel layer deposition can be attributed to the reduction of interface Ov-related defects, which agrees with the enhanced bias stress stability of the a-IGZO TFTs.展开更多
The presynaptic active zone is a dynamic structure that orchestrates regulated release of neurotrans- mitters. Developmental and aging processes, and changes in neuronal network activity can all modulate the number, s...The presynaptic active zone is a dynamic structure that orchestrates regulated release of neurotrans- mitters. Developmental and aging processes, and changes in neuronal network activity can all modulate the number, size and composition of active zone and thereby synaptic efficacy. However, very little is known about the mechanism that controls the structural stability of active zone. By study- ing a model synapse, the Drosophila neuromuscular iunction, our recent work shed light on how two scaffolding proteins at the active zone regulate active zone stability by promoting a localized dephos- phorylation event at the nerve terminal. Here we discuss the major insights from our findings and their implications for future research.展开更多
Active metamaterials incorporating with non-Foster elements have been considered as one of the means of overcoming inherent limitations of the passive counterparts, thus achieving broadband or gain metamaterials. Howe...Active metamaterials incorporating with non-Foster elements have been considered as one of the means of overcoming inherent limitations of the passive counterparts, thus achieving broadband or gain metamaterials. However, realistic active metamaterials, especially non-Foster loaded medium, would face the challenge of the possibility of instability. Moreover,they normally appear to be time-variant and in unsteady states, which leads to the necessity of a stability method to cope with the stability issue considering the system model uncertainty. In this paper, we propose an immittance-based stability method to design a non-Foster loaded metamaterial ensuring robust stability. First, the principle of this stability method is introduced after comparing different stability criteria. Based on the equivalent system model, the stability characterization is used to give the design specifications to achieve an active metamaterial with robust stability. Finally, it is applied to the practical design of active metamaterial with non-Foster loaded loop arrays. By introducing the disturbance into the nonFoster circuit(NFC), the worst-case model uncertainty is considered during the design, and the reliability of our proposed method is verified. This method can also be applied to other realistic design of active metamaterials.展开更多
The Qinghai-Tibet Plateau(QTP)distributes the largest extent of high-altitude mountain permafrost in the world(Zou et al.,2017),which has different characteristics from high-latitude permafrost(Yang et al.,2010)and st...The Qinghai-Tibet Plateau(QTP)distributes the largest extent of high-altitude mountain permafrost in the world(Zou et al.,2017),which has different characteristics from high-latitude permafrost(Yang et al.,2010)and stores massive soil carbon.展开更多
An active front steering (AFS) intervention control during braking for vehicle stability is presented. Based on the investigation of AFS mechanism, a simplified model of steering system is established and integrated...An active front steering (AFS) intervention control during braking for vehicle stability is presented. Based on the investigation of AFS mechanism, a simplified model of steering system is established and integrated with vehicle model. Then the AFS control on vehicle handling dynamics during braking is designed. Due to the difficulties associated with the sideslip angle measurement of vehicle, a state observer is designed to provide real time estimation. Thereafter, the controller with the feedback of both sideslip and yaw angle is implemented. To evaluate the system control, the proposed AFS controlled vehicle has been tested in the Hardware-in-the-loop-simulation (HILS) system and compared with that of conventional vehicle. Results show that AFS can improve vehicle lateral stability effectively without reducing the braking performance.展开更多
This paper adds a negative velocity feedback to the dynamical system of twin-tail aircraft to suppress the vibration.The system is represented by two coupled second-order nonlinear differential equations having both q...This paper adds a negative velocity feedback to the dynamical system of twin-tail aircraft to suppress the vibration.The system is represented by two coupled second-order nonlinear differential equations having both quadratic and cubic nonlinearities.The system describes the vibration of an aircraft tail subjected to both multi-harmonic and multi-tuned excitations.The method of multiple time scale perturbation is adopted to solve the nonlinear differential equations and obtain approximate solutions up to the third order approximations.The stability of the proposed analytic solution near the simultaneous primary,combined and internal resonance is studied and its conditions are determined.The effect of different parameters on the steady state response of the vibrating system is studied and discussed by using frequency response equations.Some different resonance cases are investigated numerically.展开更多
The basic concepts about the active structures and some attributes of the modes were presented in paper “Liner Active Structures and Modes]( I) ". The characteristics of the active discrete systems and active be...The basic concepts about the active structures and some attributes of the modes were presented in paper “Liner Active Structures and Modes]( I) ". The characteristics of the active discrete systems and active beams were discussed, especially, the stability of the active structures and the orthogonality of the eigenvectors. The notes about modes were portrayed by a model of a seven-storeyed building with sensors and actuators. The concept of the adjoint active structure was extended from the discrete systems to the beams that were the representations of the continuous structures. Two types of beams with different placements of the measuring and actuating systems were discussed in detail. One is the beam with the discrete sensors and actuators, and the other is the beam with distributed sensor and actuator function. The orthogonality conditions were derived with the modal shapes of the active beam and its adjoint active beam. An example shows that the variation of eigenvalues with feedback amplitude for the homo-configuration and non-homo-configuration active structures.展开更多
There has been a continuous need for high active, excellently durable and low-cost electrocatalysts for rechargeable zinc-air batteries. Among many low-cost metal based candidates, transition metal oxides with the CNT...There has been a continuous need for high active, excellently durable and low-cost electrocatalysts for rechargeable zinc-air batteries. Among many low-cost metal based candidates, transition metal oxides with the CNTs composite have gained increasing attention. In this paper, the 3-D hollow sphere MnO_2 nanotube-supported Co_3O_4 nanoparticles and its carbon nanotubes hybrid material(Co_3 O_4/MnO_2-CNTs) have been synthesized via a simple co-precipitation method combined with post-heat treatment. The morphology and composition of the catalysts are thoroughly analyzed through SEM, TEM, TEM-mapping, XRD, EDX and XPS. In comparison with the commercial 20% Pt/C, Co_3O_4/MnO_2,bare MnO_2 nanotubes and CNTs, the hybrid Co_3O_4/MnO_2-CNTs-350 exhibits perfect bi-functional catalytic activity toward oxygen reduction reaction and oxygen evolution reaction under alkaline condition(0.1 M KOH). Therefore, high cell performances are achieved which result in an appropriate open circuit voltage(~1.47 V),a high discharge peak power density(340 mW cm^(-2)) and a large specific capacity(775 mAh g^(-1) at 10 mA cm^(-2)) for the primary Zn-air battery, a small charge-discharge voltage gap and a high cycle-life(504 cycles at 10 mA cm^(-2) with 10 min per cycle) for the rechargeable Zn-air battery. In particular, the simple synthesis method is suitable for a large-scale production of this bifunctional material due to a green, cost effective and readily available process.展开更多
SnS2 nanoflakes were successfully synthesized via a simple hydrothermal process. The as-prepared SnS2 samples were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), nitrogen adsorption-de...SnS2 nanoflakes were successfully synthesized via a simple hydrothermal process. The as-prepared SnS2 samples were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), nitrogen adsorption-desorption isotherms, and UV-vis diffuse reflectance spectroscopy(DRS). The photocatalytic activities of the as-prepared SnS2 nanoflakes under visible light irradiation(λ〉420 nm) were evaluated by the degradation of rhodamine B(Rh B). The effect of hydrothermal temperatures on the photocatalytic efficiency of as-prepared SnS2 nanoflakes was investigated. The experimental result showed that SnS2 nanoflakes synthesized at the temprature of 160 o had higher photocatalytic efficiency and good photocatalytic stability.展开更多
Epilepsy is believed to be caused by a lack of balance between excitation and inhibitation in the brain. A promising strategy for the control of the disease is closed-loop brain stimulation. How to determine the stimu...Epilepsy is believed to be caused by a lack of balance between excitation and inhibitation in the brain. A promising strategy for the control of the disease is closed-loop brain stimulation. How to determine the stimulation control parameters for effective and safe treatment protocols remains, however, an unsolved question. To constrain the complex dynamics of the biological brain, we use a neural population model(NPM). We propose that a proportional-derivative(PD) type closed-loop control can successfully suppress epileptiform activities. First, we determine the stability of root loci, which reveals that the dynamical mechanism underlying epilepsy in the NPM is the loss of homeostatic control caused by the lack of balance between excitation and inhibition. Then, we design a PD type closed-loop controller to stabilize the unstable NPM such that the homeostatic equilibriums are maintained; we show that epileptiform activities are successfully suppressed. A graphical approach is employed to determine the stabilizing region of the PD controller in the parameter space, providing a theoretical guideline for the selection of the PD control parameters. Furthermore, we establish the relationship between the control parameters and the model parameters in the form of stabilizing regions to help understand the mechanism of suppressing epileptiform activities in the NPM. Simulations show that the PD-type closed-loop control strategy can effectively suppress epileptiform activities in the NPM.展开更多
Oxygen evolution reaction(OER) is one of the most important reactions in the energy storage devices such as metal–air batteries and unitized regenerative fuel cells(URFCs). However, the kinetically sluggishness o...Oxygen evolution reaction(OER) is one of the most important reactions in the energy storage devices such as metal–air batteries and unitized regenerative fuel cells(URFCs). However, the kinetically sluggishness of OER and the high prices as well as the scarcity of the most active precious metal electrocatalysts are the major bottleneck in these devices. Developing low-cost non-precious metal catalysts with high activity and stability for OER is highly desirable. A facile, in situ template method combining the dodecyl benzene sulfuric acid sodium(SDBS) assisted hydrothermal process with subsequent high-temperature treatment was developed to prepare porous Co3O4 with improved surface area and hierarchical porous structure as precious catalysts alternative for oxygen evolution reaction(OER). Due to the unique structure, the as-prepared catalyst shows higher electrocatalytic activity than Co3O4 prepared by traditional thermal-decomposition method(noted as Co3O4-T) and commercial IrO2 catalyst for OER in 0.1M KOH aqueous solution. Moreover, it displays improved stability than Co3O4-T. The results demonstrate a highly efficient, scalable, and low cost method for developing highly active and stable OER electrocatalysts in alkaline solutions.展开更多
A new compound 8-chloro-7-(4-(3-chloropropanoyl)piperazin-1-yl)-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid(II, C20H20Cl2FN3O4, Mr = 456.08) was synthesized and characterized by 1H NMR, 1...A new compound 8-chloro-7-(4-(3-chloropropanoyl)piperazin-1-yl)-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid(II, C20H20Cl2FN3O4, Mr = 456.08) was synthesized and characterized by 1H NMR, 13 C NMR, HR MS and single-crystal X-ray diffraction. X-ray powder diffraction(XRPD), thermal stabilities, UV-Vis spectrum, photoluminescent properties and absolute quantum yield of compound II were also investigated. The structure demonstrates that the crystal belongs to the triclinic system, space group P1 with a = 7.7339(3), b = 10.2396(5), c = 15.9076(8)A, α = 76.517(4), β = 77.609(4), γ = 80.320(4)°, V = 1187.22(9)A^3, Z = 2, Dc = 1.514 g/mm^3, μ = 4.901 mm^-1, F(000) = 556.0, R = 0.0534 and w R = 0.1447(I 〉 2σ(I)). The result reveals that fluoroquionolone moiety in this structure stacks with π×××π interactions to generate an infinite 1D chain, which can stabilize the whole framework of compound II. Delightfully, preliminary antibacterial activity in vitro against 4 cell strains uncovers that compound II has almost equal strong activity in comparison with Clinafloxacin, but stronger than Norfloxacin. These outcomes provide important information for further exploration of the structure-activity relationship(SAR) of compound II derivatives or analogs.展开更多
While double perovskites of PrBaCo_(2)O_(6)(PBC)have been extensively developed as the cathodes for proton-conducting solid oxide fuel cells(H-SOFCs),the effects of Sr-or Ca-doping at the A site on the activity and st...While double perovskites of PrBaCo_(2)O_(6)(PBC)have been extensively developed as the cathodes for proton-conducting solid oxide fuel cells(H-SOFCs),the effects of Sr-or Ca-doping at the A site on the activity and stability of the oxygen reduction reaction are yet to be fully studied.Here,the effect of A-site doping on the oxygen reduction reaction activity and stability has been studied by evaluating the performance of both symmetrical and single cells.It is shown that Ca-doped PBC(PrBa_(0.8)Ca_(0.2)Co_(2)O_(6),PBCC)shows a slightly smaller polarization resistance(0.076Ωcm^(2))than that(0.085Ωcm^(2))of Sr-doped PBC(PrBa0.8Sr0.2Co2O6,PBSC)at 700◦C in wet air.Moreover,the degradation rate of PBCC is 0.0003Ωcm^(2)h^(−1)(0.3%h−1)in 100 h,about 1/10 of that of PBSC at 700◦C in wet air.In addition,it is also confirmed that single cells with PBCC cathode show higher peak power density(1.22Wcm^(−2)vs.1.08Wcm^(−2)at 650◦C)and better durability(degradation rate of 0.1%h^(−1)vs.0.13%h^(−1))than those with PBSC cathode.The distribution of relaxation time analyses suggests that the better stability of the PBCC electrode may come from the fast and stable surface oxygen exchange process in the medium frequency range of the electrochemical impedance spectrum.展开更多
InP shows a very high efficiency for solar light to electricity conversion in solar cell and may present an expectation property in photocatalytic hydrogen evolution.However,it suffers serious corrosion in water dispe...InP shows a very high efficiency for solar light to electricity conversion in solar cell and may present an expectation property in photocatalytic hydrogen evolution.However,it suffers serious corrosion in water dispersion.In this paper,it is demonstrated that the stability and activity of the InP-based catalyst are effectively enhanced by applying an anti-corrosion SnO layer and In(OH)_(3)transition layer,which reduces the crystal mismatch between SnO and InP and increases charge transfer.The obtained Pt/SnO/In(OH)_(3)/InP exhibits a hydrogen production rate of 144.42μmol/g in_(3)h under visible light illumination in multi-cycle tests without remarkable decay,12_(3)times higher than that of naked In(OH)_(3)/InP without any electron donor under visible irradiation.展开更多
Polymeric-inorganic nanocomposite catalysts were synthesized by facile one-pot chemical polymerization of pyrrole in the presence of titanium dioxide nanoparticles. The electrical, optical, photovoltaic performance of...Polymeric-inorganic nanocomposite catalysts were synthesized by facile one-pot chemical polymerization of pyrrole in the presence of titanium dioxide nanoparticles. The electrical, optical, photovoltaic performance of dye sensitized solar cell(DSSC) and visible light driven photocatalytic activities of the nanocomposite were investigated. The prepared nanocomposite displays excellent photo-activity, attaining 100% degradation of methyl orange dye in 60 min under visible light source while 55% for pure TiO_2 under similar experimental conditions. The photovoltaic performance of the polypyrrole-titanium dioxide(PPy-TiO_2) nanocomposite has a 51.4% improvement with a photo-conversion efficiency of 8.07% as compared to pure TiO_2 based DSSC. By comparing the physical mixture of the PPy-TiO_2 nanocomposite and pristine TiO_2, the enhanced activity of the PPy-TiO_2 nanocomposite can be attributed to the reduced charge transfer resistance, outstanding electrical conductance of the PPy, the nano-sized structure of TiO_2 and their synergetic effect. Furthermore, the PPy-TiO_2 nanocomposite shows excellent electrical conductivity and isothermal stability under ambient conditions below 110?C.展开更多
The temperature stability of supercapacitor(SC) is largely determined by the properties of the electrolyte.Hydrogel electrolytes(HGE), due to their hydrophilic polymer skeleton, show different temperature stabilit...The temperature stability of supercapacitor(SC) is largely determined by the properties of the electrolyte.Hydrogel electrolytes(HGE), due to their hydrophilic polymer skeleton, show different temperature stability to that of liquid aqueous electrolytes. In this study, symmetric activated carbon(AC) SCs had been assembled with in situ electrodeposited poly(vinyl alcohol) potassium borate(PVAPB) HGE. The electrochemical performance of the SCs was systematically studied at different temperatures. Results show that the conductivity of PVAPB HGE is comparable with that of liquid aqueous electrolytes at different temperatures. The operating temperature range of PVAPB HGE SCs is -5–60°C, while those of the 1 mol/L Na2SO4SCs and the 0.9 mol/L KClSCs are 20–80°C and 20–40°C, respectively. The specific capacitance of PVAPB HGE SC is higher than those of SCs using liquid aqueous electrolytes at any temperature. The excellent temperature stability of PVAPB HGE makes it possible to build stable aqueous SCs in the wider temperature range.展开更多
The catalytic activity of polycobaltprotoporphyrin(PCoPP)was compared with adsorbed cobaltprotoporphyrin monolayer.The results have shown that PCoPP film shows higher catalytic activity and stability than monolayer on...The catalytic activity of polycobaltprotoporphyrin(PCoPP)was compared with adsorbed cobaltprotoporphyrin monolayer.The results have shown that PCoPP film shows higher catalytic activity and stability than monolayer on glass carbon electrode in both alkaline and acid solution. Catalytic activity of PCoPP goes through a maximum with increase of film thickness.A model was proposed to explain such dependence.The effect of film thickness and solution pH on the stability of PCoPP film was studied.展开更多
The p53 tumor suppressor is a sequence-specific transcription factor that undergoes an abundance of post-translational modifications for its regulation and activation.Acetylation of p53 is an important reversible enzy...The p53 tumor suppressor is a sequence-specific transcription factor that undergoes an abundance of post-translational modifications for its regulation and activation.Acetylation of p53 is an important reversible enzymatic process that occurs in response to DNA damage and genotoxic stress and is indispensible for p53 transcriptional activity.p53 was the first non-histone protein shown to be acetylated by histone acetyl transferases,and a number of more recent in vivo models have underscored the importance of this type of modification for p53 activity.Here,we review the current knowledge and recent findings of p53 acetylation and deacetylation and discuss the implications of these processes for the p53 pathway.展开更多
The frequency stability of free-running semiconductor lasers is influenced by several factors, such as driving current and external operating environment. The frequency stabilization of laser has become an internation...The frequency stability of free-running semiconductor lasers is influenced by several factors, such as driving current and external operating environment. The frequency stabilization of laser has become an international research hotspot in recent years. This paper reviews active frequency stabilization technologies of laser diodes and elaborates their principles. Based on differences of frequency discrimination curves, these active frequency stabilization technologies are classified into three major types, which are harmonic frequency stabilization,Pound-Drever-Hall(PDH) technology and curve subtraction frequency stabilization. Further, merits and demerits of each technology are compared from aspects of frequency stability and structure complexity. Finally, prospects of frequency stabilization technologies of semiconductor lasers are discussed in detail. Combining several of these methods are future trends, especially the combination of frequency stabilization of F–P cavity. And PID electronic control for optimizing the servo system is generally added in the methods mentioned above.展开更多
基金supported by the National Railway Group Science and Technology Program(Nos.N2020J026 and N2021J028)the Independent Research and Development Projects of Traction Power State Key Laboratory(No.2022TPL-T02),China。
文摘This paper puts forward a high-speed train bogie active stability method,based on frame lateral vibration control,for improving the stability and critical speed of railway vehicles at high speeds.Two inertial actuators apply active control forces to the front and rear end beams of the bogie frame.A scale model of bogie lateral dynamics is established,as well as the state space equation of the control system.Also,the multi-objective optimization is used to construct state feedback parameters,which take hunting stability and control effort into account.Furthermore,the effects of time-delay in the control system and suspension parameters on bogie hunting stability are studied.The dynamic behaviors and the stability mechanism of the bogie control system are analyzed.Finally,a 1:5 scale test rig is used to conduct a bogie active stability experiment.The results reveal that active control of frame lateral vibration can effectively improve the bogie system's hunting stability margin at high speeds,but time-delay in the control system cannot be ignored.
基金Supported by the National Basic Research Program of China under Grant Nos 2010CB327504,2011CB922100 and2011CB301900the National Natural Science Foundation of China under Grant Nos 11104130 and 61322112+2 种基金the Natural Science Foundation of Jiangsu Province under Grant Nos BK2011556 and BK2011050the Priority Academic Program Development of Jiangsu Higher Education Institutionsand the NUPTSF Grant Nos NY213069 and NY214028
文摘The effect of oxygen partial pressure (Po2) during the channel layer deposition on bias stability of amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFTs) is investigated. As Po2 increases from 10% to 30%, it is found that the device shows enhanced bias stress stability with significantly reduced threshold voltage drift under positive gate bias stress. Based on the x-ray photoelectron spectroscopy measurement, the concentration of oxygen vacancies (Or) within the a-IGZO layer is suppressed by increasing Po2. Meanwhile, the low-frequency noise analysis indicates that the average trap density near the channel/dielectric interface continuously drops with increasing Po2. Therefore, the improved interface quality with increasing Po2 during the channel layer deposition can be attributed to the reduction of interface Ov-related defects, which agrees with the enhanced bias stress stability of the a-IGZO TFTs.
文摘The presynaptic active zone is a dynamic structure that orchestrates regulated release of neurotrans- mitters. Developmental and aging processes, and changes in neuronal network activity can all modulate the number, size and composition of active zone and thereby synaptic efficacy. However, very little is known about the mechanism that controls the structural stability of active zone. By study- ing a model synapse, the Drosophila neuromuscular iunction, our recent work shed light on how two scaffolding proteins at the active zone regulate active zone stability by promoting a localized dephos- phorylation event at the nerve terminal. Here we discuss the major insights from our findings and their implications for future research.
基金Project supported by the National Natural Science Foundation of China(Grant No.61701349)the Natural Science Foundation of Shandong Province,China(Grant Nos.ZR2017QF012 and ZR2017MF042)the Program for the Top Young Innovative Talents,China(Grant No.Q1313-03)
文摘Active metamaterials incorporating with non-Foster elements have been considered as one of the means of overcoming inherent limitations of the passive counterparts, thus achieving broadband or gain metamaterials. However, realistic active metamaterials, especially non-Foster loaded medium, would face the challenge of the possibility of instability. Moreover,they normally appear to be time-variant and in unsteady states, which leads to the necessity of a stability method to cope with the stability issue considering the system model uncertainty. In this paper, we propose an immittance-based stability method to design a non-Foster loaded metamaterial ensuring robust stability. First, the principle of this stability method is introduced after comparing different stability criteria. Based on the equivalent system model, the stability characterization is used to give the design specifications to achieve an active metamaterial with robust stability. Finally, it is applied to the practical design of active metamaterial with non-Foster loaded loop arrays. By introducing the disturbance into the nonFoster circuit(NFC), the worst-case model uncertainty is considered during the design, and the reliability of our proposed method is verified. This method can also be applied to other realistic design of active metamaterials.
基金financially supported by the National Natural Science Foundation of China(41871064)the Second Tibetan Plateau Scientific Expedition and Research Program(2019QZKK0304)。
文摘The Qinghai-Tibet Plateau(QTP)distributes the largest extent of high-altitude mountain permafrost in the world(Zou et al.,2017),which has different characteristics from high-latitude permafrost(Yang et al.,2010)and stores massive soil carbon.
文摘An active front steering (AFS) intervention control during braking for vehicle stability is presented. Based on the investigation of AFS mechanism, a simplified model of steering system is established and integrated with vehicle model. Then the AFS control on vehicle handling dynamics during braking is designed. Due to the difficulties associated with the sideslip angle measurement of vehicle, a state observer is designed to provide real time estimation. Thereafter, the controller with the feedback of both sideslip and yaw angle is implemented. To evaluate the system control, the proposed AFS controlled vehicle has been tested in the Hardware-in-the-loop-simulation (HILS) system and compared with that of conventional vehicle. Results show that AFS can improve vehicle lateral stability effectively without reducing the braking performance.
基金the support of the author community in using REVTEX, offering suggestions and encouragement, testing new versions
文摘This paper adds a negative velocity feedback to the dynamical system of twin-tail aircraft to suppress the vibration.The system is represented by two coupled second-order nonlinear differential equations having both quadratic and cubic nonlinearities.The system describes the vibration of an aircraft tail subjected to both multi-harmonic and multi-tuned excitations.The method of multiple time scale perturbation is adopted to solve the nonlinear differential equations and obtain approximate solutions up to the third order approximations.The stability of the proposed analytic solution near the simultaneous primary,combined and internal resonance is studied and its conditions are determined.The effect of different parameters on the steady state response of the vibrating system is studied and discussed by using frequency response equations.Some different resonance cases are investigated numerically.
文摘The basic concepts about the active structures and some attributes of the modes were presented in paper “Liner Active Structures and Modes]( I) ". The characteristics of the active discrete systems and active beams were discussed, especially, the stability of the active structures and the orthogonality of the eigenvectors. The notes about modes were portrayed by a model of a seven-storeyed building with sensors and actuators. The concept of the adjoint active structure was extended from the discrete systems to the beams that were the representations of the continuous structures. Two types of beams with different placements of the measuring and actuating systems were discussed in detail. One is the beam with the discrete sensors and actuators, and the other is the beam with distributed sensor and actuator function. The orthogonality conditions were derived with the modal shapes of the active beam and its adjoint active beam. An example shows that the variation of eigenvalues with feedback amplitude for the homo-configuration and non-homo-configuration active structures.
基金financial support from the National Natural Science Foundation of China (U1510120, 91645110)the Project of Introducing Overseas Intelligence High Education of China (2017-2018)+1 种基金the Graduate Thesis Innovation Foundation of Donghua University (EG2016034)the College of Environmental Science and Engineering, State Environmental Protection Engineering Center for Pollution Treatment and Control in Textile Industry, Donghua University
文摘There has been a continuous need for high active, excellently durable and low-cost electrocatalysts for rechargeable zinc-air batteries. Among many low-cost metal based candidates, transition metal oxides with the CNTs composite have gained increasing attention. In this paper, the 3-D hollow sphere MnO_2 nanotube-supported Co_3O_4 nanoparticles and its carbon nanotubes hybrid material(Co_3 O_4/MnO_2-CNTs) have been synthesized via a simple co-precipitation method combined with post-heat treatment. The morphology and composition of the catalysts are thoroughly analyzed through SEM, TEM, TEM-mapping, XRD, EDX and XPS. In comparison with the commercial 20% Pt/C, Co_3O_4/MnO_2,bare MnO_2 nanotubes and CNTs, the hybrid Co_3O_4/MnO_2-CNTs-350 exhibits perfect bi-functional catalytic activity toward oxygen reduction reaction and oxygen evolution reaction under alkaline condition(0.1 M KOH). Therefore, high cell performances are achieved which result in an appropriate open circuit voltage(~1.47 V),a high discharge peak power density(340 mW cm^(-2)) and a large specific capacity(775 mAh g^(-1) at 10 mA cm^(-2)) for the primary Zn-air battery, a small charge-discharge voltage gap and a high cycle-life(504 cycles at 10 mA cm^(-2) with 10 min per cycle) for the rechargeable Zn-air battery. In particular, the simple synthesis method is suitable for a large-scale production of this bifunctional material due to a green, cost effective and readily available process.
基金Funded by the National Natural Science Foundation of China(No.U1304520)the Education Department of Henan Province(2013GGJS-185)
文摘SnS2 nanoflakes were successfully synthesized via a simple hydrothermal process. The as-prepared SnS2 samples were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), nitrogen adsorption-desorption isotherms, and UV-vis diffuse reflectance spectroscopy(DRS). The photocatalytic activities of the as-prepared SnS2 nanoflakes under visible light irradiation(λ〉420 nm) were evaluated by the degradation of rhodamine B(Rh B). The effect of hydrothermal temperatures on the photocatalytic efficiency of as-prepared SnS2 nanoflakes was investigated. The experimental result showed that SnS2 nanoflakes synthesized at the temprature of 160 o had higher photocatalytic efficiency and good photocatalytic stability.
基金supported by the National Natural Science Foundation of China(Grant Nos.61473208,61025019,and 91132722)ONR MURI N000141010278NIH grant R01EY016281
文摘Epilepsy is believed to be caused by a lack of balance between excitation and inhibitation in the brain. A promising strategy for the control of the disease is closed-loop brain stimulation. How to determine the stimulation control parameters for effective and safe treatment protocols remains, however, an unsolved question. To constrain the complex dynamics of the biological brain, we use a neural population model(NPM). We propose that a proportional-derivative(PD) type closed-loop control can successfully suppress epileptiform activities. First, we determine the stability of root loci, which reveals that the dynamical mechanism underlying epilepsy in the NPM is the loss of homeostatic control caused by the lack of balance between excitation and inhibition. Then, we design a PD type closed-loop controller to stabilize the unstable NPM such that the homeostatic equilibriums are maintained; we show that epileptiform activities are successfully suppressed. A graphical approach is employed to determine the stabilizing region of the PD controller in the parameter space, providing a theoretical guideline for the selection of the PD control parameters. Furthermore, we establish the relationship between the control parameters and the model parameters in the form of stabilizing regions to help understand the mechanism of suppressing epileptiform activities in the NPM. Simulations show that the PD-type closed-loop control strategy can effectively suppress epileptiform activities in the NPM.
基金supported by the Youth Innovation Promotion Association(no.2015147)CAS and National Program on Key Basic Research Project(973 Program,2012CB215500)+1 种基金the Outstanding Youngest Scientist FoundationChinese Academy of Sciences(CAS)
文摘Oxygen evolution reaction(OER) is one of the most important reactions in the energy storage devices such as metal–air batteries and unitized regenerative fuel cells(URFCs). However, the kinetically sluggishness of OER and the high prices as well as the scarcity of the most active precious metal electrocatalysts are the major bottleneck in these devices. Developing low-cost non-precious metal catalysts with high activity and stability for OER is highly desirable. A facile, in situ template method combining the dodecyl benzene sulfuric acid sodium(SDBS) assisted hydrothermal process with subsequent high-temperature treatment was developed to prepare porous Co3O4 with improved surface area and hierarchical porous structure as precious catalysts alternative for oxygen evolution reaction(OER). Due to the unique structure, the as-prepared catalyst shows higher electrocatalytic activity than Co3O4 prepared by traditional thermal-decomposition method(noted as Co3O4-T) and commercial IrO2 catalyst for OER in 0.1M KOH aqueous solution. Moreover, it displays improved stability than Co3O4-T. The results demonstrate a highly efficient, scalable, and low cost method for developing highly active and stable OER electrocatalysts in alkaline solutions.
基金financially supported by the National Natural Science Foundation of China(No.21542003)
文摘A new compound 8-chloro-7-(4-(3-chloropropanoyl)piperazin-1-yl)-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid(II, C20H20Cl2FN3O4, Mr = 456.08) was synthesized and characterized by 1H NMR, 13 C NMR, HR MS and single-crystal X-ray diffraction. X-ray powder diffraction(XRPD), thermal stabilities, UV-Vis spectrum, photoluminescent properties and absolute quantum yield of compound II were also investigated. The structure demonstrates that the crystal belongs to the triclinic system, space group P1 with a = 7.7339(3), b = 10.2396(5), c = 15.9076(8)A, α = 76.517(4), β = 77.609(4), γ = 80.320(4)°, V = 1187.22(9)A^3, Z = 2, Dc = 1.514 g/mm^3, μ = 4.901 mm^-1, F(000) = 556.0, R = 0.0534 and w R = 0.1447(I 〉 2σ(I)). The result reveals that fluoroquionolone moiety in this structure stacks with π×××π interactions to generate an infinite 1D chain, which can stabilize the whole framework of compound II. Delightfully, preliminary antibacterial activity in vitro against 4 cell strains uncovers that compound II has almost equal strong activity in comparison with Clinafloxacin, but stronger than Norfloxacin. These outcomes provide important information for further exploration of the structure-activity relationship(SAR) of compound II derivatives or analogs.
基金Natural Science Foundation of Guangdong Province,Grant/Award Number:2021A1515010395Fundamental Research Funds for the Central Universities,Grant/Award Number:2022ZYGXZR002+2 种基金National Natural Science Foundation of China,Grant/Award Numbers:22179039,22005105Pearl River Talent Recruitment Program,Grant/Award Number:2019QN01C693Guangdong Innovative and Entrepreneurial Research Team Program,Grant/Award Number:2021ZT09L392。
文摘While double perovskites of PrBaCo_(2)O_(6)(PBC)have been extensively developed as the cathodes for proton-conducting solid oxide fuel cells(H-SOFCs),the effects of Sr-or Ca-doping at the A site on the activity and stability of the oxygen reduction reaction are yet to be fully studied.Here,the effect of A-site doping on the oxygen reduction reaction activity and stability has been studied by evaluating the performance of both symmetrical and single cells.It is shown that Ca-doped PBC(PrBa_(0.8)Ca_(0.2)Co_(2)O_(6),PBCC)shows a slightly smaller polarization resistance(0.076Ωcm^(2))than that(0.085Ωcm^(2))of Sr-doped PBC(PrBa0.8Sr0.2Co2O6,PBSC)at 700◦C in wet air.Moreover,the degradation rate of PBCC is 0.0003Ωcm^(2)h^(−1)(0.3%h−1)in 100 h,about 1/10 of that of PBSC at 700◦C in wet air.In addition,it is also confirmed that single cells with PBCC cathode show higher peak power density(1.22Wcm^(−2)vs.1.08Wcm^(−2)at 650◦C)and better durability(degradation rate of 0.1%h^(−1)vs.0.13%h^(−1))than those with PBSC cathode.The distribution of relaxation time analyses suggests that the better stability of the PBCC electrode may come from the fast and stable surface oxygen exchange process in the medium frequency range of the electrochemical impedance spectrum.
文摘InP shows a very high efficiency for solar light to electricity conversion in solar cell and may present an expectation property in photocatalytic hydrogen evolution.However,it suffers serious corrosion in water dispersion.In this paper,it is demonstrated that the stability and activity of the InP-based catalyst are effectively enhanced by applying an anti-corrosion SnO layer and In(OH)_(3)transition layer,which reduces the crystal mismatch between SnO and InP and increases charge transfer.The obtained Pt/SnO/In(OH)_(3)/InP exhibits a hydrogen production rate of 144.42μmol/g in_(3)h under visible light illumination in multi-cycle tests without remarkable decay,12_(3)times higher than that of naked In(OH)_(3)/InP without any electron donor under visible irradiation.
基金supports of this work by KFUPM through the project # R15-CW-11 (MIT-13103, 13104) under the Center of Excellence for Scientific Research Collaboration with MIT and the project # RG 1311
文摘Polymeric-inorganic nanocomposite catalysts were synthesized by facile one-pot chemical polymerization of pyrrole in the presence of titanium dioxide nanoparticles. The electrical, optical, photovoltaic performance of dye sensitized solar cell(DSSC) and visible light driven photocatalytic activities of the nanocomposite were investigated. The prepared nanocomposite displays excellent photo-activity, attaining 100% degradation of methyl orange dye in 60 min under visible light source while 55% for pure TiO_2 under similar experimental conditions. The photovoltaic performance of the polypyrrole-titanium dioxide(PPy-TiO_2) nanocomposite has a 51.4% improvement with a photo-conversion efficiency of 8.07% as compared to pure TiO_2 based DSSC. By comparing the physical mixture of the PPy-TiO_2 nanocomposite and pristine TiO_2, the enhanced activity of the PPy-TiO_2 nanocomposite can be attributed to the reduced charge transfer resistance, outstanding electrical conductance of the PPy, the nano-sized structure of TiO_2 and their synergetic effect. Furthermore, the PPy-TiO_2 nanocomposite shows excellent electrical conductivity and isothermal stability under ambient conditions below 110?C.
文摘The temperature stability of supercapacitor(SC) is largely determined by the properties of the electrolyte.Hydrogel electrolytes(HGE), due to their hydrophilic polymer skeleton, show different temperature stability to that of liquid aqueous electrolytes. In this study, symmetric activated carbon(AC) SCs had been assembled with in situ electrodeposited poly(vinyl alcohol) potassium borate(PVAPB) HGE. The electrochemical performance of the SCs was systematically studied at different temperatures. Results show that the conductivity of PVAPB HGE is comparable with that of liquid aqueous electrolytes at different temperatures. The operating temperature range of PVAPB HGE SCs is -5–60°C, while those of the 1 mol/L Na2SO4SCs and the 0.9 mol/L KClSCs are 20–80°C and 20–40°C, respectively. The specific capacitance of PVAPB HGE SC is higher than those of SCs using liquid aqueous electrolytes at any temperature. The excellent temperature stability of PVAPB HGE makes it possible to build stable aqueous SCs in the wider temperature range.
文摘The catalytic activity of polycobaltprotoporphyrin(PCoPP)was compared with adsorbed cobaltprotoporphyrin monolayer.The results have shown that PCoPP film shows higher catalytic activity and stability than monolayer on glass carbon electrode in both alkaline and acid solution. Catalytic activity of PCoPP goes through a maximum with increase of film thickness.A model was proposed to explain such dependence.The effect of film thickness and solution pH on the stability of PCoPP film was studied.
文摘The p53 tumor suppressor is a sequence-specific transcription factor that undergoes an abundance of post-translational modifications for its regulation and activation.Acetylation of p53 is an important reversible enzymatic process that occurs in response to DNA damage and genotoxic stress and is indispensible for p53 transcriptional activity.p53 was the first non-histone protein shown to be acetylated by histone acetyl transferases,and a number of more recent in vivo models have underscored the importance of this type of modification for p53 activity.Here,we review the current knowledge and recent findings of p53 acetylation and deacetylation and discuss the implications of these processes for the p53 pathway.
基金Project supported by the National Ministry of Science and Technology and Key Research Project 973(Nos.2014CB340102,2017YFF0104601)the Preeminence Youth Fund of China(No.61625504)the National Natural Science Foundation of China(Nos.61527820,11674313,61535014,61727815)
文摘The frequency stability of free-running semiconductor lasers is influenced by several factors, such as driving current and external operating environment. The frequency stabilization of laser has become an international research hotspot in recent years. This paper reviews active frequency stabilization technologies of laser diodes and elaborates their principles. Based on differences of frequency discrimination curves, these active frequency stabilization technologies are classified into three major types, which are harmonic frequency stabilization,Pound-Drever-Hall(PDH) technology and curve subtraction frequency stabilization. Further, merits and demerits of each technology are compared from aspects of frequency stability and structure complexity. Finally, prospects of frequency stabilization technologies of semiconductor lasers are discussed in detail. Combining several of these methods are future trends, especially the combination of frequency stabilization of F–P cavity. And PID electronic control for optimizing the servo system is generally added in the methods mentioned above.