Stabilization strategy of a car-following model with multiple time delays of the drivers

An extended car-following model with multiple delays is constructed to describe driver's driving behavior.Through stability analysis,the stability condition of this uncontrolled model is given.To dampen the negative impact of the driver's multiple delays(i.e.,stability condition is not satisfied),a novel control strategy is proposed to assist the driver in adjusting vehicle operation.The control strategy consists of two parts:the design of control term as well as the design of the parameters in the term.Bifurcation analysis is performed to illustrate the necessity of the design of parameters in control terms.In the course of the design of parameters in the control term,we improve the definite integral stability method to reduce the iterations by incorporating the characteristics of bifurcation,which can determine the appropriate parameters in the control terms more quickly.Finally,in the case study,we validate the control strategy by utilizing measured data and configuring scenario,which is closer to the actual traffic.The results of validation show that the control strategy can effectively stabilize the unstable traffic flow caused by driver's delays.

Stable attenuation-compensated reverse time migration and its application to land seismic data

Intrinsic attenuation of the earth causes energy loss and phase distortion in seismic wave propagation.To obtain high-resolution imaging results,these negative effects must be considered during reverse time migration(RTM).We can easily implement attenuation-compensated RTM using the constant Q viscoacoustic wave equation with decoupled amplitude attenuation and phase dispersion terms.However,the nonphysical amplitude-compensation process will inevitably amplify the high-frequency noise in the wavefield in an exponential form,causing the numerical simulation to become unstable.This is due to the fact that the amplitude of the compensation grows exponentially with frequency.In order to achieve stable attenuation-compensated RTM,we modify the analytic expression of the attenuation compensation extrapolation operator and make it only compensate for amplitude loss within the effective frequency band.Based on this modified analytic formula,we then derive an explicit time-space domain attenuation compensation extrapolation operator.Finally,the implementation procedure of stable attenuation-compensated RTM is presented.In addition to being simple to implement,the newly proposed attenuation-compensated extrapolation operator is superior to the conventional low-pass filter in suppressing random noise,which will further improve the imaging resolution.We use two synthetic and one land seismic datasets to verify the stability and effectiveness of the proposed attenuationcompensated RTM in improving imaging resolution in viscous media.

Achieving efficient N_(2)electrochemical reduction by stabilizing the N2H*intermediate with the frustrated Lewis pairs

Electrocatalytic nitrogen reduction reaction(eNRR)with sustainable energy under ambient conditions represents an attractive approach to producing ammonia,but the design of the-state-of-the-art electrocatalyst with high efficiency and selectivity still faces formidable challenges.In contrast to traditional eNRR catalyst design strategies focusing on N≡N triple bond activation,we herein theoretically proposed an alternative strategy to improve eNRR performance via stabilizing the N_(2)H^(*)intermediate using catalysts with the frustrated Lewis pairs(FLPs),i.e.,transition metal(TM)atoms and boron(B)atom co-doped 2D black phosphorus(TM-B@BP).Our density functional theory(DFT)results reveal that the TM atom donates electrons to the adsorbed N_(2)molecule,while B atom provides empty orbital to stabilize the adsorption of N_(2)H^(*)intermediate.This framework successfully identifies five promising candidates(i.e.,Ti-B@BP,V-B@BP,Cr-B@BP,Mn-B@BP and Fe-B@BP)with low theoretical limiting potentials(−0.60,−0.41,−0.45,−0.43 and−0.50 V,respectively)and high selectivity for eNRR.We believe that the intermediate stabilization strategy introduced in current work offers a new opportunity to achieve accelerated and cost-effective ammonia synthesis with electrocatalysis.

The Stabilizing Role of Material Structure in Scientific Practice

Knowledge of the environment is essential for the survival of organisms; but those organisms have to have the capacity to stabilize such knowledge. The aim of this article is to analyze the various strategies for stabilizing human knowledge, with a special focus on its material anchors and their interactions with other stabilization means. In particular, I consider how such stabilization is reflected in scientific activity and practice, and what its repercussions are for the models of science that have dominated the philosophical landscape of the 20th century. My starting hypothesis will be that the role of material anchors in stabilizing conceptual blends is analogous to that of technology in grounding scientific knowledge. The framework I adopt with regard to conceptualization is that of Fauconnier and Turner （2002） on conceptual blends. Just as technology intervenes in scientific practice in conjunction with conceptual elements, so do material anchors, which conjoin other non-material strategies of knowledge stabilization. Endowing knowledge with a material basis may be understood firstly as an element （sometimes a key element） for representing knowledge and offering an explanation, and secondly as a way of providing a scientific hypothesis with empirical grounding. It is this second sense that connects with scientific experimentation and the use of instruments and technology.

Recent Advances in Stability Improvement Strategies of M-N_(x)/C Catalysts Towards Oxygen Reduction Reaction

Although fuel cells possess advantages of high energy conversion efficiency and zero-carbon emission,their large-scale commercialization is restricted by expensive and scarce platinum(Pt)catalysts.Metal-nitrogen-carbon(M-Nx/C)catalysts are hailed as the most promising candidates to replace Pt due to their considerable oxygen reduction reaction(ORR)activity and low cost.Despite tremendous progress in terms of active site identification and activity improvement being achieved in the past few decades,the M-Nx/C catalysts still suffer from insufficient durability,which drastically limits their practical application.In this regard,understanding degradation mechanisms and customizing stabilization strategies are of significant importance yet challengeable.In this review,we summarize the recent advances in the stability improvement of M-Nx/C catalysts.The stability test protocols of the M-Nx/C are firstly introduced.Subsequently,with the combination of advanced ex situ and in situ characterization techniques and density functional theory calculation,we present a comprehensive overview of the main degradation mechanisms during ORR process.Aiming at these deactivation issues,a variety of novel improvement strategies are developed to enhance the stability of M-Nx/C.Finally,the current challenges and prospects to design highly stable M-Nx/C catalysts are also proposed.

Preparation of Perovskite Solar Cells in the Air:Degradation Mechanism and Prospects on Large-Area Fabrication

The preparation of perovskite solar cells(PsCs)in the air environment has attracted the attention of numerous experimenters due to its low preparation cost and the possibility of commercialization.Although the power conversion efficiency(PCE)of PSCs has increased rapidly and exceeded 25%,which is comparable to commercial polysilicon solar cells,most certified or reported high-efficiency perovskite solar cells are still confined to glove boxes or relatively small active areas in the air environment due to moisture,oxygen,high temperature,and ultraviolet(UV)factors.In this review.

Advanced Strategies for Stabilizing Single‑Atom Catalysts for Energy Storage and Conversion

Well-defined atomically dispersed metal catalysts(or single-atom catalysts)have been widely studied to fundamentally under-stand their catalytic mechanisms,improve the catalytic efficiency,increase the abundance of active components,enhance the catalyst utilization,and develop cost-effective catalysts to effectively reduce the usage of noble metals.Such single-atom cata-lysts have relatively higher selectivity and catalytic activity with maximum atom utilization due to their unique characteristics of high metal dispersion and a low-coordination environment.However,freestanding single atoms are thermodynamically unstable,such that during synthesis and catalytic reactions,they inevitably tend to agglomerate to reduce the system energy associated with their large surface areas.Therefore,developing innovative strategies to stabilize single-atom catalysts,including mass-separated soft landing,one-pot pyrolysis,co-precipitation,impregnation,atomic layer deposition,and organometallic complexation,is critically needed.Many types of supporting materials,including polymers,have been commonly used to stabilize single atoms in these fabrication techniques.Herein,we review the stabilization strategies of single-atom catalyst,including different synthesis methods,specific metals and carriers,specific catalytic reactions,and their advantages and disadvantages.In particular,this review focuses on the application of polymers in the synthesis and stabilization of single-atom catalysts,including their functions as carriers for metal single atoms,synthetic templates,encapsulation agents,and protection agents during the fabrication process.The technical challenges that are currently faced by single-atom catalysts are summarized,and perspectives related to future research directions including catalytic mechanisms,enhancement of the catalyst loading content,and large-scale implementation are proposed to realize their practical applications.

The Unique Strategies of Flight Initiation Adopted by Butterflies on Vertical Surfaces

As the basis of flight behavior,the initiation process of insect flight is accompanied by a transition from crawling mode to flight mode,and is clearly important and complex.Insects take flight from a vertical surface,which is more difficult than takeoff from a horizontal plane,but greatly expands the space of activity and provides us with an excellent bionic model.In this study,the entire process of a butterfly alighting from a vertical surface was captured by a high-speed camera system,and the movements of its body and wings were accurately measured for the first time.After analyzing the movement of the center of mass,it was found that before initiation,the acceleration perpendicular to the wall was much greater than the acceleration parallel to the wall,reflecting the positive effects of the legs during the initiation process.However,the angular velocity of the body showed that this process was unstable,and was further destabilized as the flight speed increased.Comparing the angles between the body and the vertical direction before and after leaving the wall,a significant change in body posture was found,evidencing the action of aerodynamic forces on the body.The movement of the wings was further analyzed to obtain the laws of the three Euler angles,thus revealing the locomotory mechanism of the butterfly taking off from the vertical surface.