摘要：Compared to the traditional lumped-parameter model, computational fluid dynamics （CFD） attracted more attentions due to facilitating more accurate reactor design and optimization methods when analyzing the heat transfer in the industrial packed bed. Here, a model was developed based on the CFD theory, in which the heterogeneous fluid flow was resolved by considering the oscillatory behavior of voidage and the effective fluid viscosity. The energy transports in packed bed were calculated by the convection and diffusion incorporated with gaseous dispersion in fluid and the contacting thermal conductivity of packed particles in solids. The heat transfer coefficient between fluid and wall was evaluated by considering the turbulence due to the packed particles adjacent to the wall. Thus, the heat transfer in padded bed can be predicted without using any adjustable semi-empirical effective thermal conductivity coefficient. The experimental results from the literature were employed to validate this model.

摘要：Intelligent structures like zero Poisson’s ratio(ZPR)cellular structures have been widely applied to the engineering fields such as morphing wings in recent decades,owing to their outstanding characteristics including light weight and low effective modulus. In-plane and out-of-plane mechanical properties of ZPR cellular structures are investigated in this paper. A theoretical method for calculating in-plane tensile modulus,in-plane shear modulus and out-of-plane bending modulus of ZPR cellular structures is proposed,and the impacts of the unit cell geometrical configurations on in-plane tensile modulus,in-plane shear modulus and out-of-plane bending modulus are studied systematically based on finite element(FE)simulation. Experimental tests validate the feasibility and effectiveness of the theoretical and FE analysis. And the results show that the in-plane and out-of-plane mechanical properties of ZPR cellular structures can be manipulated by designing cell geometrical parameters.

摘要：To gain a deep insight into the hot drawing process of aluminum alloy sheet, simulations of cylindrical cup drawing at elevated temperatures were carried out with experimental validation. The influence of four important process parameters, namely,punch velocity, blank holder force(BHF), friction coefficient and initial forming temperature of blank on drawing characteristics(*** thickness and thickness deviation) was investigated with the help of design of experiments(DOE), analysis of variance(ANOVA) and analysis of mean(ANOM). Based on the results of ANOVA, it is shown that the blank holder force has the greatest influence on minimum thickness. The importance of punch velocity for thickness deviation is 44.35% followed by BHF of 24.88%,friction coefficient of 15.77% and initial forming temperature of blank of 14.995%. After determining the significance of each factor on forming characteristics, how the individual parameter affects characteristics was further analyzed by ANOM.

摘要：Since LiOsO_3 was discovered, obtaining easy-accessible polar metals for research and applications has been challenging. In this paper, we present a multilayer design strategy, which is configured as ferroelectric layer/carrier reservoir layer/isolation layer/substrate, for obtaining polar metals by electrostatically doping a strained ferroelectric material in a more effective way. In the proposed configuration, both 1 unit-cell thick BaTiO_3 and PbTiO_3 exhibited considerable Ti off-centering with various strains,which should extend the applicability of ferroelectric-based polar metals in ultra-thin devices. Moreover, engineered by the compressive strain and the BaTiO_3 thickness, the design strategy effectively achieved polar metallicity and dimensionalitytunable electronic states associated with the modulation of highly anisotropic properties such as electrical and electronic thermal conductivity, which may be helpful for designing ultra-thin, ultrafast, and low-power switch devices.

摘要：An investigation of the effect of simplifying bogie regions on the aerodynamic performance of a high-speed train was carried out by studying four train models,to explore possible ways to optimise the train underbody structure,improve the underbody aerodynamic performance,and reduce the aerodynamic *** shear stress transport(SST)k-ωturbulence model was used to study the airflow features of the high-speed train with different bogie regions at Re=2.25×10^(6).The calculated aerodynamic drag and surface pressure were compared with the experimental benchmark of wind tunnel *** results show that the SST k-ωmodel presents high accuracy in predicting the flow fields around the train,and the numerical results closely agree with the experimental *** with the train with simplified bogies,the aerodynamic drag of the train with a smooth surface and the train with enclosed bogie cavities/inter-carriage gaps decreases by 38.2%and 30.3%,respectively,while it increases by 10.8%for the train with cavities but no ***,enclosing bogie cavities shows a good capability of aerodynamic drag reduction for a new generation of highspeed trains.

摘要：The development of a high-performing pseudocapacitor requires a comprehensive understanding of electrode materials from the aspects of electron transfer and electrolyte ion adsorption and ***,these factors are considered over the prototype TiO_(2),and a high pseudocapacitance is achieved via the introduction of various defects,i.e.,oxygen defect(V_(O))and co-doped defect(V_(O)+N_(O)).The study is based on joint explorations of first-principle calculations and the transfer matrix *** to pristine TiO_(2)(300 F g^(-1)),defective TiO_(2) produces pseudocapacitance as high as 1700 F g^(-1).Moreover,defects induce small barriers for electron transmission caused by surface band *** climbing image nudged elastic band diffusion of H ions displays a much higher barrier in TiO_(2)-V_(O) than in TiO_(2)-V_(O)+N_(O).Such a result indicates easy H diffusion in the co-doped *** work provides insights into the adsorption and diffusion of electrolyte ions and the influence of defects on electron *** results are also significant for the design and optimization of electrode materials for the next generation of supercapacitors.

摘要：In the past few decades,we have seen the rapid development of bioactive materials which can repair damaged tissues and save human ***,researchers have sought to develop bioactive materials with unique physical and chemical properties,such as stiffness,functional groups,nanotopographies and stimulus-responsive properties,to promote tissue regeneration at the biointerface.

摘要：The discovery of superconductivity at Tc = 26 K in fluorine-doped LaFeAsO [1] has led to the subsequent findings of dozens of new superconducting materials in the class of Fe-based superconductors (FeSCs)[2,3]. All those FeSCs were found to possess antifluorite-like Fe2X2 (X = As, Se) layers which were believed to be the crucial structural motif for the emergence of high-temperature superconductivity. This common feature makes it possible to design a new FeSC with the crystal chemistry [3-5]. For example, with the consideration of the intergrowth of BaFe2As2 and BaTi2As2O, the new FeSC Ba2Fe2Ti2As4O (Tc=21 K) was discovered [6]. The block-layer-design approach was also demonstrated to be effective for other class of layered materials, such as Eu3Bi2S4F4 [7], LaPb- BiS3O [8], La5Cu4As4O4C12 [9], Pb5BiFe3O10Cl2 [10], and Bi4Q4CU1.7Se2.7CI03 [11].

摘要：Brake friction materials with different zinc powder contents(0,2,4,6,8 wt.%)were fabricated via powder metallurgy *** results indicate that with the increasing zinc powder content,the density and thermal conductivity of the materials gradually increase,while the hardness decreases *** increasing zinc powder content,the curve of the nominal friction coefficient shows fluctuating trend but the lowest friction coefficient also shows an ***,the wear rate and braking noise of the friction material monotonously decrease with increasing zinc *** effect may be attributed to the transformation of the tribological mechanism from adhesive wear and abrasive wear to adhesive *** brake friction material with 4 wt.%zinc powder exhibits both the best tribological and noise performance.

摘要：Bridges crossing active faults are more likely to suffer serious damage or even collapse due to the wreck capabilities of near-fault pulses and surface ruptures under *** a high-speed railway simply-supported girder bridge with eight spans crossing an active strike-slip fault as the research object,a refined coupling dynamic model of the high-speed train-CRTS III slab ballastless track-bridge system was established based on *** rationality of the established model was thoroughly *** horizontal ground motions in a fault rupture zone were simulated and transient dynamic analyses of the high-speed train-track-bridge coupling system under 3-dimensional seismic excitations were subsequently *** safe running speed limits of a high-speed train under different earthquake levels(frequent occurrence,design and rare occurrence)were assessed based on wheel-rail dynamic(lateral wheel-rail force,derailment coefficient and wheel-load reduction rate)and rail deformation(rail dislocation,parallel turning angle and turning angle)*** optimization was then investigated in terms of the rail fastener stiffness and isolation layer friction *** of the wheel-rail dynamic indicators demonstrate the safe running speed limits for the high-speed train to be approximately 200 km/h and 80 km/h under frequent and design earthquakes,while the train is unable to run safely under rare *** addition,the rail deformations under frequent,design and rare earthquakes meet the safe running requirements of the high-speed train for the speeds of 250,100 and 50 km/h,*** speed limits determined for the wheel-rail dynamic indicators are lower due to the complex coupling effect of the train-track-bridge system under track *** running safety of the train was improved by increasing the fastener stiffness and isolation layer friction *** the rail fastener lateral stiffness of 60 kN/mm and isolat