摘要：In this paper,a hybrid integrated broadband Doherty power amplifier(DPA)based on a multi-chip module(MCM),whose active devices are fabricated using the gallium nitride(GaN)process and whose passive circuits are fabricated using the gallium arsenide(GaAs)integrated passive device(IPD)process,is proposed for 5G massive multiple-input multiple-output(MIMO)*** inverted DPA structure with a low-Q output network is proposed to achieve better bandwidth performance,and a single-driver architecture is adopted for a chip with high gain and small *** proposed DPA has a bandwidth of 4.4-5.0 GHz that can achieve a saturation of more than 45.0 *** gain compression from 37 dBm to saturation power is less than 4 dB,and the average power-added efficiency(PAE)is 36.3%with an 8.5 dB peak-to-average power ratio(PAPR)in 4.5-5.0 *** measured adjacent channel power ratio(ACPR)is better than
50 dBc after digital predistortion(DPD),exhibiting satisfactory linearity.

摘要：Attaining a decarbonized and sustainable energy system,which is the core solution to global energy issues,is accessible through the development of hydrogen ***-exchange membrane water electrolyzers(PEMWEs)are promising devices for hydrogen production,given their high efficiency,rapid responsiveness,and *** plates account for a relatively high percentage of the total cost and weight compared with other components of ***,optimization of their design may accelerate the promotion of *** paper reviews the advances in materials and flow-field design for bipolar ***,the working conditions of proton-exchange membrane fuel cells(PEMFCs)and PEMWEs are compared,including reaction direction,operating temperature,pressure,input/output,and ***,the current research status of bipolar-plate substrates and surface coatings is summarized,and some typical channel-rib flow fields and porous flow fields are ***,the effects of materials on mass and heat transfer and the possibility of reducing corrosion by improving the flow field structure are ***,this review discusses the potential directions of the development of bipolar-plate design,including material fabrication,flow-field geometry optimization using threedimensional printing,and surface-coating composition optimization based on computational materials science.

摘要：Solid solution-strengthened copper alloys have the advantages of a simple composition and manufacturing process,high mechanical and electrical comprehensive performances,and low cost;thus,they are widely used in high-speed rail contact wires,electronic component connectors,and other *** the contradiction between low alloying and high performance is an important challenge in the development of solid solution-strengthened copper *** the typical solid solution-strengthened alloy Cu-4Zn-1Sn as the research object,we proposed using the element In to replace Zn and Sn to achieve low alloying in this *** new alloys,Cu-1.5Zn-1Sn-0.4In and Cu-1.5Zn-0.9Sn-0.6In,were designed and *** total weight percentage content of alloying elements decreased by 43%and 41%,respectively,while the product of ultimate tensile strength(UTS)and electrical conductivity(EC)of the annealed state increased by 14%and 15%.After cold rolling with a 90%reduction,the UTS of the two new alloys reached 576 and 627MPa,respectively,the EC was 44.9%IACS and 42.0%IACS,and the product of UTS and EC(UTS×EC)was 97%and 99%higher than that of the annealed state *** dislocations proliferated greatly in cold-rolled alloys,and the strengthening effects of dislocations reached 332 and 356 MPa,respectively,which is the main reason for the considerable improvement in mechanical properties.

摘要：Traditional 3Ni weathering steel cannot completely meet the requirements for offshore engineering development,resulting in the design of novel 3Ni steel with the addition of microalloy elements such as Mn or Nb for strength enhancement becoming a *** stress-assisted corrosion behavior of a novel designed high-strength 3Ni steel was investigated in the current study using the corrosion big data *** information on the corrosion process was recorded using the galvanic corrosion current monitoring *** gradi-ent boosting decision tree(GBDT)machine learning method was used to mine the corrosion mechanism,and the importance of the struc-ture factor was *** exposure tests were conducted to verify the calculated results using the GBDT *** indic-ated that the GBDT method can be effectively used to study the influence of structural factors on the corrosion process of 3Ni ***-ferent mechanisms for the addition of Mn and Cu to the stress-assisted corrosion of 3Ni steel suggested that Mn and Cu have no obvious effect on the corrosion rate of non-stressed 3Ni steel during the early stage of *** the corrosion reached a stable state,the in-crease in Mn element content increased the corrosion rate of 3Ni steel,while Cu reduced this *** the presence of stress,the increase in Mn element content and Cu addition can inhibit the corrosion *** corrosion law of outdoor-exposed 3Ni steel is consistent with the law based on corrosion big data technology,verifying the reliability of the big data evaluation method and data prediction model selection.

摘要：Shearing dislocation is a common failure type for rock–backfill interfaces because of backfill sedimentation and rock strata movement in backfill mining *** paper designed a test method for rock–backfill shearing *** digital image techno-logy and three-dimensional(3D)laser morphology scanning techniques,a set of 3D models with rough joint surfaces was ***,the mechanical behavior of rock–backfill shearing dislocation was investigated using a direct shear *** effects of interface roughness on the shear–displacement curve and failure characteristics of rock–backfill specimens were *** 3D fractal dimen-sion,profile line joint roughness coefficient(JRC),profile line two-dimensional fractal dimension,and the surface curvature of the frac-tures were *** correlation characterization of surface roughness was then analyzed,and the shear strength could be measured and calculated using *** results showed the following:there were three failure threshold value points in rock–backfill shearing dis-location:30%–50%displacement before the peak,70%–90%displacement before the peak,and 100%displacement before the peak to post-peak,which could be a sign for rock–backfill shearing dislocation *** surface JRC could be used to judge the rock–backfill shearing dislocation failure,including post-peak sliding,uniform variations,and gradient change,corresponding to rock–backfill disloca-tion failure on the field *** research reveals the damage mechanism for rock–backfill complexes based on the free joint surface,fills the gap of existing shearing theoretical systems for isomerism complexes,and provides a theoretical basis for the prevention and control of possible disasters in backfill mining.

摘要：Nonreciprocity of thermal metamaterials has significant application prospects in isolation protection,unidirectional transmission,and energy ***,due to the inherent isotropic diffusion law of heat flow,it is extremely difficult to achieve nonreciprocity of heat *** review presents the recent developments in thermal nonreciprocity and explores the fundamental theories,which underpin the design of nonreciprocal thermal metamaterials,i.e.,the Onsager reciprocity ***,three methods for achieving nonreciprocal metamaterials in the thermal field are elucidated,namely,nonlinearity,spatiotemporal modulation,and angular momentum bias,and the applications of nonreciprocal thermal metamaterials are *** also discuss nonreciprocal thermal ***,the potential applications of nonreciprocity to other Laplacian physical fields are ***,the prospects for advancing nonreciprocal thermal metamaterials are highlighted,including developments in device design and manufacturing techniques and machine learning-assisted material design.

摘要：Due to the long-term plate tectonic movements in southwestern china,the in-situ stress field in deep formations is *** passing through deep soft-rock mass under non-hydrostatic high in-situ stress field,tunnels will suffer serious asymmetric *** is no available support design method for tunnels under such a situation in existing studies to clarify the support time and support *** study first analyzed the mechanical behavior of tunnels in non-hydrostatic in-situ stress field and derived the theoretical equations of the ground squeezing curve(GSC)and ground loosening curve(GLC).Then,based on the convergence confinement theory,the support design method of deep soft-rock tunnels under non-hydrostatic high in-situ stress field was established considering both squeezing and loosening *** addition,this method can provide the clear support time and support stiffness of the second layer of initial *** proposed design method was applied to the Wanhe tunnel of the china-Laos railway in *** data indicated that the optimal support scheme had a good effect on controlling the tunnel deformation in non-hydrostatic high in-situ stress *** applications showed that the secondary lining could be constructed properly.

摘要：Non-pillar mining technology with automatically formed roadway is a new mining method without coal pillar reservation and roadway *** stability control of automatically formed roadway is the key to the successful application of the new *** order to realize the stability control of the roadway surrounding rock,the mechanical model of the roof and rib support structure is established,and the influence mechanism of the automatically formed roadway parameters on the compound force is *** this basis,the roof and rib support structure technology of confined lightweight concrete is proposed,and its mechanical tests under different eccentricity are carried *** results show that the bearing capacity of confined lightweight concrete specimens is basically the same as that of ordinary confined concrete *** bearing capacity of confined lightweight concrete specimens under different eccentricities is 1.95 times higher than those of U-shaped steel *** comparing the test results with the theoretical calculated results of the confined concrete,the calculation method of the bearing capacity for the confined lightweight concrete structure is *** design method of confined lightweight concrete support structure is established,and is successfully applied in the extra-large mine,Ningtiaota Coal Mine,china.

摘要：The problems associated with vibrations of viaducts and low-frequency structural noise radiation caused by train excitation continue to increase in importance.A new floating-slab track vibration isolator-non-obstructive particle damping-phononic crystal vibration isolator is proposed herein,which uses the particle damping vibration absorption technology and bandgap vibration control *** vibration reduction performance of the NOPD-PCVI was analyzed from the perspective of vibration *** paper explores the structure-borne noise reduction performance of the NOPD-PCVIs installed on different bridge structures under varying service conditions encountered in practical engineering *** load transferred to the bridge is obtained from a coupled train-FST-bridge analytical model considering the different structural parameters of *** vibration responses are obtained using the finite element method,while the structural noise radiation is simulated using the frequency-domain boundary element *** the particle swarm optimization algorithm,the parameters of the NOPD-PCVI are optimized so that its frequency bandgap matches the dominant bridge structural noise frequency *** noise reduction performance of the NOPD-PCVIs is compared to the steel-spring isolation under different service conditions.

摘要：Metalenses with achromatic performance offer a new opportunity for high-quality imaging with an ultracompact configuration;however,they suffer from complex fabrication processes and low focusing *** this study,we propose an efficient design method for achromatic microlenses on a wavelength scale using materials with low dispersion,an adequately designed convex surface,and a thickness profile *** taking into account the absolute chromatic aberration,relative focal length shift(FLS),and numerical aperture(NA),microlens with a certain focal length can be realized through our realized map of geometric ***,the designed achromatic microlenses with low-dispersion fused silica were fabricated using a focused ion beam,and precise surface profiles were *** fabricated microlenses exhibited a high average focusing efficiency of 65%at visible wavelengths of 410-680 nm and excellent achromatic capability via white light ***,the design exhibited the advantages of being polarization-insensitive and *** results demonstrate the effectiveness of our proposed achromatic microlens design approach,which expands the prospects of miniaturized optics such as virtual and augmented reality,ultracompact microscopes,and biological endoscopy.