PVDF-assisted pyrolysis strategy for corrugated plate oxygen electrocatalysis nanoreactor:Simultaneously realizing efficient active sites and rapid mass transfer

Though Zn-air batteries(ZABs)are one of the most promising system for energy storage and conversion,challenge still persists in its commercial application due to the sluggish kinetics of oxygen reduction/evolution reaction(ORR/OER).Hereby,a polyvinylidene fluoride(PVDF)-assisted pyrolysis strategy is proposed to develop a novel corrugated plate-like bifunctional electrocatalyst using two-dimensional zeolitic imidazolate frameworks(2D ZIF-67)as the precursor.The employed PVDF plays an important role in inheriting the original 2D structure of ZIF-67 and modulating the composition of the final products.As a result,a corrugated plate-like electrocatalyst,high-density Co nanoparticles decorated 2D Co,N,and F tri-doped carbon nanosheets,can be obtained.The acquired electrocatalyst enables efficient active sites and rapid mass transfer simultaneously,thus showing appreciable electrocatalytic performance for rechargeable Zn-air batteries.Undoubtedly,our proposed strategy offers a new perspective to the design of advanced oxygen electrocatalysts.

Configuring single-layer MXene nanosheet onto natural wood fiber via C-Ti-C covalent bonds for high-stability Li-S batteries

Lithium-sulfur batteries(LSBs)are considered promising candidates for next-generation battery technologies owing to their outstanding theoretical energy density and cost-effectiveness.However,the low conductivity and polysulfide shuttling effect of S cathodes severely hamper the practical performance of LSBs.Herein,in situ-generated single layer MXene nanosheet/hierarchical porous carbonized wood fiber(MX/PCWF)composites are prepared via a nonhazardous eutectic activation strategy coupled with pyrolysis-induced gas diffusion.The unique architecture,wherein single layer MXene nanosheets are constructed on carbonized wood fiber walls,ensures rapid polysulfide conversion and continuous electron transfer for redox reactions.The C-Ti-C bonds formed between MXene and PCWF can considerably expedite the conversion of polysulfides,effectively suppressing the shuttle effect.An impressive capacity of 1301.1 m A h g^(-1)at 0.5 C accompanied by remarkable stability is attained with the MX/PCWF host,as evidenced by the capacity maintenance of 722.6 m A h g^(-1)after 500 cycles.Notably,the MX/PCWF/S cathode can still deliver a high capacity of 886.8 m A h g^(-1)at a high S loading of 5.6 mg cm^(-2).The construction of two-dimensional MXenes on natural wood fiber walls offers a competitive edge over S-based cathode materials and demonstrates a novel strategy for developing high-performance batteries.

国家标准《建筑隔震设计标准》编制与说明

汶川地震后,建筑隔震技术日益受到重视。《建筑隔震设计标准》从筹备到完成报批稿编制,先后历经8年,汇集了28家编制单位的成果,征求了两百多位专家和技术人员的意见,在充分参考现行相关标准条文的基础上,发展并确立了以"直接设计法""复振型分解反应谱法"和新一代隔震设计反应谱为代表性内容的方法体系,将于近期颁布。本文对《建筑隔震设计标准》的核心内容进行了简要介绍,包括内容总述、标准创新点、关键问题、设计算例、应用意义等,供科研和技术人员参考。

Circular Formation Flight Control for Unmanned Aerial Vehicles With Directed Network and External Disturbance

This paper proposes a new distributed formation flight protocol for unmanned aerial vehicles(UAVs)to perform coordinated circular tracking around a set of circles on a target sphere.Different from the previous results limited in bidirectional networks and disturbance-free motions,this paper handles the circular formation flight control problem with both directed network and spatiotemporal disturbance with the knowledge of its upper bound.Distinguishing from the design of a common Lyapunov fiunction for bidirectional cases,we separately design the control for the circular tracking subsystem and the formation keeping subsystem with the circular tracking error as input.Then the whole control system is regarded as a cascade connection of these two subsystems,which is proved to be stable by input-tostate stability(ISS)theory.For the purpose of encountering the external disturbance,the backstepping technology is introduced to design the control inputs of each UAV pointing to North and Down along the special sphere(say,the circular tracking control algorithm)with the help of the switching function.Meanwhile,the distributed linear consensus protocol integrated with anther switching anti-interference item is developed to construct the control input of each UAV pointing to east along the special sphere(say,the formation keeping control law)for formation keeping.The validity of the proposed control law is proved both in the rigorous theory and through numerical simulations.

In-situ self-templated preparation of porous core-shell Fe_(1-x)S@N,S co-doped carbon architecture for highly efficient oxygen reduction reaction

Transition metal compound(TMC)/carbon hybrids,as prospering electrocatalyst,have attracted great attention in the field of oxygen reduction reaction(ORR).Their morphology,structure and composition often play a crucial role in determining the ORR performance.In this work,we for the first time report the successful fabrication of porous core-shell Fe_(1-x)S@N,S co-doped carbon(Fe_(1-x)S@NSC-t,t represents etching time)by a novel in-situ self-template induced strategy using Fe3O4 nanospheres and pyrrole as sacrificial self-template.The post-polymerization of pyrrole can be accomplished by the Fe^(3+)released through the etching of Fe_(3)O_(4) by HCl acid.Thus,the etching time has a significant effect on the morphology,structure,composition a nd ORR performance of Fe_(1-x)S@NSC-t.Based on the cha racterizations,we find Fe_(1-x)S@NSC-24 can realize effective and balanced combination of Fe_(1-x)S and NSC,possessing porous core-shell architecture,optimized structure defect,specific surface area and doped heteroatoms configurations(especially for pyridinic N,graphitic N and Fe-N structure).These features thus lead to outstanding catalytic activity and cycling stability towards ORR.Our work provides a good guidance on the design of TMC/carbon-based electrodes with unique stable morphology and optimized structure and composition.

Coordinated Adaptive Control for Coordinated Path-following Surface Vessels with a Time-invariant Orbital Velocity

This article considers the problem of directing a family of fully actuated surface vessels to cooperatively follow a set of convex and closed orbits with a time-invariant reference orbital velocity and maintain attitude synchronization. A consensusbased adaptive control law under a bidirectional communication topology is proposed to estimate the reference orbital velocity so that the restriction that every vessel in the family must have access to the reference in the previous literature can be removed.The assumption of nonzero total linear speed of each vessel is removed by the use of potential function. Simulation results demonstrate the effectiveness of the proposed approach.

受时空调制电网控制的动态声子晶体

宽频弹性波衰减技术在现代工程应用中有不可或缺的地位.本文提出了一种基于时间/空间调制电网和压电材料的动态声子晶体并进行了实验验证.该动态声子晶体可以在多频带上实现对弯曲波传输的衰减,并对衰减频带进行调控.压电分流电路为机械模态和电模态提供了能量交换的同时也产生了布拉格带隙.该动态声子晶体仅需对电网进行时间/空间调制以实现可调制的宽频带弯曲波衰减.其中,通过对电网进行空间调制可实现两条布拉格带隙从而扩大了机电耦合以及弯曲波衰减的频率范围.另一方面,时间调制使机电耦合的模态频率产生线性平移从而生成了多条时间-布拉格带隙.更重要的是,本文提供了一种简易的弯曲波带隙调谐方式,即只对单一电阻进行控制.相关实验也进一步验证了时间/空间调制对弯曲波传输的影响.该动态声子晶体可以为下一代可调谐的多频带滤波器等设备提供新思路.

In Situ Embedment of ZnS Nanocrystals in High Porosity Carbon Fibers as an Advanced Anode Material for Efcient Lithium Storage

ZnS is a promising material for lithium-ion battery anodes due to its abundant natural resources,simplicity of synthesis,and high theoretical lithium storage capacity.However,it needs to be optimized for its low conductivity and volume efect during the charge–discharge process.The traditional method of combining with carbonaceous materials is usually laborious,and the required sulfuration process may possibly result in the destruction of materials morphology.In this study,hybrid materials formed by the combination of ZnS nanocrystals and high porosity carbon fbers were synthesized by one-step electrospinning using zinc diethyldithiocarbamate and polyacrylonitrile as raw materials and poly(ethylene glycol)—block-poly(propylene glycol)—block-poly(ethylene glycol)as template.The method is simple and avoids the infuence of sulfuration process on the morphology of materials.The composite presents a specifc capacity of 592.2 mAh g^(−1) under a current density of 1 A g^(−1) after 1000 cycles.The porous structure signifcantly decreases the difusion mean-free path of Li+and inhibits the volume efect associated with the lithium storage process of ZnS.In addition,the 3D cross-linked carbon fbers improve the conductivity of materials.This study can serve as an inspiration for the development of other lithium storage composites.

力电耦合主动超材料及其弹性波调控

超材料是实现新奇弹性波调控功能的关键所在.其中,被动超材料最先被研究者关注,目前已实现了波动阻隔、负折射、波聚焦、绕射隐身等反常波动效果,因此被动超材料在低频减振降噪、结构健康监测和波动能量收集等方面有着广泛的应用前景.然而,被动超材料在制备完成后,其等效属性和波控功能很难再根据实际需求进行调节,限制了其在真实工作环境中的应用.近年来出现的力电耦合超材料能够实现波动性质的主动调节,突破了被动超材料的限制,因此受到越来越多的关注.力电耦合超材料在微结构材料组分和拓扑构型之外引入多物理场耦合效应来改变等效属性,并能通过外部电场控制实现特定的非常规属性或者材料属性的主动甚至自适应调节.本文首先介绍力电耦合超材料的基本概念.然后,根据外部电场作用方式的不同将力电耦合超材料分为两类;并从等效属性的电场调控机理、耦合电场/微结构设计和波控功能等方面,对力电耦合超材料的研究现状和发展趋势进行了详尽的介绍和讨论.最后,针对波动控制的功能拓展、宽低频实现机理、动态均匀化以及高效数值预报等方面,对未来力电耦合超材料的研究方向与应用领域进行展望.

Kir2.1 Channel Regulation of Glycinergic Transmission Selectively Contributes to Dynamic Mechanical Allodynia in a Mouse Model of Spared Nerve Injury

Neuropathic pain is a chronic debilitating symptom characterized by spontaneous pain and mechanical allodynia. It occurs in distinct forms, including brushevoked dynamic and filament-evoked punctate mechanical allodynia. Potassium channel 2.1(Kir2.1), which exhibits strong inward rectification, is and regulates the activity of lamina I projection neurons. However, the relationship between Kir2.1 channels and mechanical allodynia is still unclear. In this study, we first found that pretreatment with ML133, a selective Kir2.1 inhibitor, by intrathecal administration, preferentially inhibited dynamic, but not punctate, allodynia in mice with spared nerve injury(SNI).Intrathecal injection of low doses of strychnine, a glycine receptor inhibitor, selectively induced dynamic, but not punctate allodynia, not only in na¨?ve but also in ML133-pretreated mice. In contrast, bicuculline, a GABAAreceptor antagonist, induced only punctate, but not dynamic,allodynia. These results indicated the involvement of glycinergic transmission in the development of dynamic allodynia. We further found that SNI significantly suppressed the frequency, but not the amplitude, of the glycinergic spontaneous inhibitory postsynaptic currents(gly-sIPSCs) in neurons on the lamina II-III border of the spinal dorsal horn, and pretreatment with ML133 prevented the SNI-induced gly-sIPSC reduction. Furthermore, 5 days after SNI, ML133, either by intrathecal administration oracute bath perfusion, and strychnine sensitively reversed the SNI-induced dynamic, but not punctate, allodynia and the gly-sIPSC reduction in lamina IIi neurons, respectively.In conclusion, our results suggest that blockade of Kir2.1 channels in the spinal dorsal horn selectively inhibits dynamic, but not punctate, mechanical allodynia by enhancing glycinergic inhibitory transmission.

Finite-time coordinated path-following control of leader-following multi-agent systems

This paper presents applications of the continuous feedback method to achieve path-following and a formation moving along the desired orbits within a finite time.It is assumed that the topology for the virtual leader and followers is directed.An additional condition of the so-called barrier function is designed to make all agents move within a limited area.A novel continuous finite-time path-following control law is first designed based on the barrier function and backstepping.Then a novel continuous finite-time formation algorithm is designed by regarding the path-following errors as disturbances.The settling-time properties of the resulting system are studied in detail and simulations are presented to validate the proposed strategies.

Osteoarthritis animal models for biomaterial-assisted osteochondral regeneration

Clinical therapeutics for the regeneration of osteochondral defects(OCD)in the early stages of osteoarthritis remain an enormous challenge in orthopaedics.For in-depth studies of tissue engineering and regenerative medicine in terms of OCD treatment,the utility of an optimal OCD animal model is crucial for assessing the effects of implanted biomaterials on the repair of damaged osteochondral tissues.Currently,the most frequently used in vivo animal models for OCD regeneration include mice,rats,rabbits,dogs,pigs,goats,sheep,horses and nonhuman primates.However,there is no single“gold standard”animal model to accurately recapitulate human disease in all aspects,thus understanding the benefits and limitations of each animal model is critical for selecting the most suitable one.In this review,we aim to elaborate the complex pathological changes in osteoarthritic joints and to summarise the advantages and limitations of OCD animal models utilised for biomaterial testing along with the methodology of outcome assessment.Furthermore,we review the surgical procedures of OCD creation in different species,and the novel biomaterials that promote OCD regeneration.Above all,it provides a significant reference for selection of an appropriate animal model for use in preclinical in vivo studies of biomaterial-assisted osteochondral regeneration in osteoarthritic joints.