Recent progress and challenges in structural construction strategy of metal-based catalysts for nitrate electroreduction to ammonia

Ammonia plays an essential role in human production and life as a raw material for chemical fertilizers.The nitrate electroreduction to ammonia reaction(NO_(3)RR)has garnered attention due to its advantages over the Haber-Bosch process and electrochemical nitrogen reduction reaction.Therefore,it represents a promising approach to safeguard the ecological environment by enabling the cycling of nitrogen species.This review begins by discussing the theoretical insights of the NO_(3)RR.It then summarizes recent advances in catalyst design and construction strategies,including alloying,structure engineering,surface engineering,and heterostructure engineering.Finally,the challenges and prospects in this field are presented.This review aims to guide for enhancing the efficiency of electrocatalysts in the NO_(3)RR,and offers insights for converting NO_(3)-to NH_(3).

Research on the Reform of the Course“Reading of Concrete Structure Plan and Construction Drawings”Under the Background of“Promoting Teaching and Learning Through Competitions”

The inherent teaching approach can no longer meet the demands of society.In this paper,current issues within the teaching landscape of architectural engineering technology in higher vocational colleges as well as the policies and teaching demands that formed the basis of this model were analyzed.The study shows the importance of the implementation of the teaching model“promoting teaching and learning through competitions.”This model puts emphasis on the curriculum and teaching resources,while also integrating the teaching process and evaluation with competition.These efforts aim to drive education reform in order to better align with the objectives of vocational education personnel training,while also acting as a reference for similar courses.

Dynamic behavior of reinforced concrete frame structure during construction

The effects of concrete's time-variant elastic modulus,casting structural components,assembling temporary shoring framework system,and shock by operating construction equipment on dynamic behavior of the reinforced concrete frame structure during construction were investigated. The dynamic tests of an eight-storey reinforced concrete frame structure during full-scaled stages of the sixth storey construction cycle were carried out by ambient vibration. Natural frequencies,corresponding mode shapes and damping ratio were determined by power spectrum processing the tested signal data in frequency domain. The changes of frequencies,mode shapes and damping ratios at different construction stages were given. The results show that natural frequencies and modal damping ratios reach the maximum at stage of casting fresh concrete,especially for higher modes. Modal damping ratios at each construction stage are less than 5% of those during usage.

Rapid excavation with a newly developed retaining system: Spiral assembly steel structure

The spiral assembly steel structure, a newly developed retaining wall for the rapid excavation of small-sized foundation pits in unsaturated soil, is presented. This new type of retaining structure is prefabricated in the factory and is assembled on site in the excavation of a pit. This retaining structure is composed of several prefabricated steel structural units, in which the adjacent steel structural units are joined with connectors. Each steel structural unit has one steel pipe in the radial direction and is welded to a single piece of steel plate. After full installation in situ, the retaining structure becomes a cylindrical steel structure. With the protection afforded by this new type of retaining structure, excavation work can be completed within 24 h to a depth up to 5 m. In order to verify the reliability and effectiveness of this new retaining structure, field construction tests were conducted in Beijing, China. The test construction was monitored. The monitoring program included measuring stress in the structure, lateral earth pressure, and lateral deformation of the surrounding soil. The monitoring data from the field test were compared with the theoretical results. The results show that the proposed new structure is reliable and effective.

Microstructures and Mechanical Properties of a New Multi-functional 460 MPa Grade Construction Structural Steel

This article reports a new generation of Q460 multi-functional construction structural steel,which has high strength(yield strength larger than 460 MPa),excellent toughness(higher than 110 J/cm^(2) at-60 ℃),lower yield ratio(lower than 0.8),good fire resistance(yield strength at 600 ℃ larger than two-thirds of its room-temperature yield strength)and better corrosion resistance.The eff ects of finish cooling temperature(FCT)on the microstructure and properties were studied by scanning electron microscopy(SEM),transmission electron microscopy(TEM),emission electron probe micro-analysis(EPMA),electron backscattering diff raction(EBSD),tensile tester,impact tester,periodic immersion cycle acceleration test and electrochemical experiment.The results show that the strength and toughness are simultaneously improved by decreasing the FCT due to more lath-like bainite with large number of dislocations,refined martensite/austenite(M/A)with higher carbon concentration and increased high angle boundaries.In addition,the fire resistance of the newly developed Q460 steel is obviously better than the conventional one,which is mainly due to non-recrystallized lath-like bainite with high dislocation density at elevated temperature.The corrosion resistance of the new Q460 steel is also improved due to the addition of Cu and Cr.

Enhancing electromagnetic wave absorption in carbon fiber using FeS_(2)nanoparticles

Carbon-based electromagnetic wave absorbing materials(absorbers)adhered with metallic sulfide nanoparticles of good electrical conductivity attract increasing researchers’attention.In this study,on the basis of carbon fiber(C_(f))@Fe_(3)O_(4) nanocomposites obtained by the electrostatic spinning and reflow method,C_(f)@FeS_(2)nanocomposite was successfully prepared during a further hydrothermal process.The products exhibit excellent electromagnetic wave absorption performances with a minimum reflection loss(RLmin)of-54.11 dB at 2.13 mm matching thickness.At the same time,the optimal effective absorption bandwidth(EAB)value of 6.04 GHz at a thickness of 1.98 mm covers the whole Ku band,suggesting its excellent electromagnetic wave absorption performances.In addition,the interlaced network structure constructed by carbon fiber,outstanding conductivity of FeS_(2)nanoparticles,and interfacial polarization from hetero-structure play significant parts in enhancing the electromagnetic parameters and absorption performances.All these results suggest that the C_(f)@FeS_(2)nanocomposites can be taken as a new electromagnetic wave-absorbing material under their low density,simple craft,and strong absorption characteristics.

THE TRACE IDENTITY, A POWERFUL TOOL FOR CONSTRUCTING THE HAMILTONIAN STRUCTURE OF INTEGRABLE SYSTEMS (Ⅱ)

An isospectral problem with four potentials is discussed. The corresponding hierarchy of nonlinearevolution equations is derived. It is shown that the AKNS, Levi, D-AKNS hierarchies and a new oneare reductions of the above hierarchy. In each case the relevant Hamiltonian form is established bymaking use of the trase identity.

On Hamiltonian realization of time-varying nonlinear systems

This paper Investigates Hamiltonian realization of time-varying nonlinear （TVN） systems, and proposes a number of new methods for the problem. It is shown that every smooth TVN system can be expressed as a generalized Hamiltonian system if the origin is the equilibrium of the system. If the Jacooian matrix of a TVN system is nonsingular, the system has a generalized Hamiltonian realization whose structural matrix and Hamiltonian function are given explicitly. For the case that the Jacobian matrix is sin- gular; this paper provides a constructive decomposition method, and then proves that a TVN system has a generalized Hamiltonian realization if its Jacobian matrix has a non- singular main diagonal block. Furthermore, some sufficient （necessary and sufficient） conditions for dissipative Hamiltonian realization of TVN systems are also presented in this paper.

COMPUTER PROGRAM FOR DIRECTED STRUCTURE TOPOLOGY OPTIMIZATION

To compensate for the imperfection of traditional bi-directional evolutionary structural optimization, material interpolation scheme and sensitivity filter functions are introduced. A suitable filter can overcome the checkerboard and mesh-dependency. And the historical information on accurate elemental sensitivity numbers are used to keep the objective function converging steadily. Apart from rational intervals of the relevant important parameters, the concept of distinguishing between active and non-active elements design is proposed, which can be widely used for improving the function and artistry of structures directly, especially for a one whose accurate size is not given. Furthermore, user-friendly software packages are developed to enhance its accessibility for practicing engineers and architects. And to reduce the time cost for large timeconsuming complex structure optimization, parallel computing is built-in in the MATLAB codes. The program is easy to use for engineers who may not be familiar with either FEA or structure optimization. And developers can make a deep research on the algorithm by changing the MATLAB codes. Several classical examples are given to show that the improved BESO method is superior for its handy and utility computer program software.

Multilayer core-shell nanostructures for enhanced 808 nm responsive upconversion

The construction of core-shell structure is an effective strategy for promoting the emission efficiency of upconversion nanocrystals(UCNCs). In this work, the UCNCs based on Nd-doping with a multilayer coreshell nanostructure are fabricated toward achieving efficient upconversion for 808 nm excitation, which have great potential for optical applications, especially photobiological applications.

Molecular simulation-based research on antifreeze peptides:advances and perspectives

Antifreeze protein(AFP)can inhibit the growth of ice crystals to protect organisms from freezing damage,and demonstrates broad application prospects in food industry.Antifreeze peptides(AFPP)are specifi c peptides with functional domains showing antifreeze activity in AFP.Bioinformatics-based molecular simulation technology can more accurately explain the properties and mechanisms of biological macromolecules.Therefore,the binding stability of antifreeze peptides and antifreeze proteins(AFP(P))to ice and the molecular-scale growth kinetics of ice were analyzed by molecular simulation,which can make up for the limitations of experimental technology.This review concludes the molecular simulation-based research in the inhibition’s study of AFP(P)on ice growth,including sequence prediction,structure construction,molecular docking and molecular dynamics(MD)studies of AFP(P)on ice applications in growth inhibition.Finally,the review prospects the future direction of designing new antifreeze biomimetic materials through molecular simulation and machine learning.The information presented in this paper will help enrich our understanding of AFPP.