Generation and Suppression of Pendant Droplet Oscillation in Electron Beam Directed Energy Deposition

Electron beam–directed energy deposition(EB–DED)has emerged as a promising wire-based metal additive manufacturing technique.However,the effects of EBs on pendant droplets at wire tips have not yet been determined.The aim of this study is to enhance the understanding of this action by analyzing the mechanism of droplet oscillation.The pendant droplet oscillation phenomenon hinders the stable transfer of droplets to the molten pool and limits the feasibility of manufacturing complex lattice structures by EB–DED.Hence,another aim of this study is to create an oscillation suppression method.An escalating asymmetric amplitude is the main characteristic of droplet oscillation.The primary oscillationinducing force is the recoil force generated from the EB-acted local surface of the droplet.The physical mechanism of this force is the rapid increase and uneven distribution of the local surface temperature caused by the partial action of the EB.The prerequisites for droplet oscillation include vacuum conditions,high power densities,and bypass wire feeding processes.The proposed EB–dynamic surrounding melting(DSM)method can be applied to conveniently and effectively suppress oscillations,enable the accurate transfer of droplets to the molten pool,and achieve stable processes for preparing the strut elements of lattice structures.Lowering the temperature and improving the uniformity of its distribution are the mechanisms of oscillation suppression in EB–DSM.In this study,the physical basis for interpreting the mechanism by which EBs act on droplets and the technical basis for using EB–DED to prepare complex lattice structure parts are provided.

Artificial Self-Recovery Opens up a New Journey of Autonomous Health of Mechanical Equipments

1.Introduction With the implementation of modern production strategies,such as“Industry 4.0”and“Made in China 2025,”the development of high-end mechanical equipment is gradually reaching a high degree of parameterization,digitalization,networking,and intelligence[1].High-end mechanical equipment no longer consists of traditional single devices,but is closely linked to the overall production process;that is,a variety of devices interact with each other and collectively form a complex system.However,faults can lead to production delays throughout the system and even seriously threaten the safety of workers[2].In addition,equipment operating in unmanned air or space vehicles(including space robots)cannot be repaired by humans if they break down[3].Until recently,the typical method of addressing machine faults was primarily the“fault cure”method,which involves manually shutting down,inspecting,and repairing the equipment to restore normal operation.Accordingly,the maintenance cycle of the traditional“fault cure”method is time-consuming,and the quality of the maintenance depends on the skills of the technician[4].

Metal organic framework supported niobium pentoxide nanoparticles with exceptional catalytic effect on hydrogen storage behavior of MgH_(2)

Nb_(2)O_(5)nanoparticles with an average particle size of 10 nm supported on a rhombic dodecahedral metal organic framework(MOF)were successfully synthesized by a facile one-pot hydrothermal reaction and subsequent calcination process.Experimental results demonstrated that the prepared catalyst drastically improved the hydrogen storage behavior of MgH_(2).7 wt%Nb_(2)O_(5)@MOF doped MgH_(2)started to desorb hydrogen at 181.9℃and 6.2 wt%hydrogen could be released within 2.6 min and 6.3 min at 275℃and 250℃,respectively.The fully dehydrogenated composite also displayed excellent hydrogenation by decreasing the onset absorption temperature to 25℃and taking up4.9 wt%and 6.5 wt%hydrogen within 6 min at 1750C and 1500C,respectively.Moreover,the corresponding activation energy was calculated to be 75.57±4.16 kJ mol^(-1)for desorption reaction and 51.38±1.09 kJ mol^(-1)for absorption reaction.After 20 cycles,0.5 wt%hydrogen capacity was lost for the MgH_(2)+7 wt%Nb_(2)O_(5)@MOF composite,much lower than 1.5 wt%of the MgH_(2)+7 wt%Nb_(2)O_(5)composite.However,the addition of Nb_(2)O_(5)@MOF had limited effect on reducing the dehydrogenation enthalpy of MgH_(2).Microstructure analysis revealed that Nb_(2)O_(5)particles were uniformly distributed on surface of the MgH_(2)matrix and synergistically improved the hydrogen storage property of MgH_(2)with MOF.

FeCoNiCrMo high entropy alloy nanosheets catalyzed magnesium hydride for solid-state hydrogen storage

The catalytic effect of FeCoNiCrMo high entropy alloy nanosheets on the hydrogen storage performance of magnesium hydride(MgH_(2))was investigated for the first time in this paper.Experimental results demonstrated that 9wt%FeCoNiCrMo doped MgH_(2)started to dehydrogenate at 200℃and discharged up to 5.89wt%hydrogen within 60 min at 325℃.The fully dehydrogenated composite could absorb3.23wt%hydrogen in 50 min at a temperature as low as 100℃.The calculated de/hydrogenation activation energy values decreased by44.21%/55.22%compared with MgH_(2),respectively.Moreover,the composite’s hydrogen capacity dropped only 0.28wt%after 20 cycles,demonstrating remarkable cycling stability.The microstructure analysis verified that the five elements,Fe,Co,Ni,Cr,and Mo,remained stable in the form of high entropy alloy during the cycling process,and synergistically serving as a catalytic union to boost the de/hydrogenation reactions of MgH_(2).Besides,the FeCoNiCrMo nanosheets had close contact with MgH_(2),providing numerous non-homogeneous activation sites and diffusion channels for the rapid transfer of hydrogen,thus obtaining a superior catalytic effect.

Enhanced Harris Hawks Optimization Integrated with Coot Bird Optimization for Solving Continuous Numerical Optimization Problems

Harris Hawks Optimization(HHO)is a novel meta-heuristic algorithm that imitates the predation characteristics of Harris Hawk and combines Lévy flight to solve complex multidimensional problems.Nevertheless,the basic HHO algorithm still has certain limitations,including the tendency to fall into the local optima and poor convergence accuracy.Coot Bird Optimization(CBO)is another new swarm-based optimization algorithm.CBO originates from the regular and irregular motion of a bird called Coot on the water’s surface.Although the framework of CBO is slightly complicated,it has outstanding exploration potential and excellent capability to avoid falling into local optimal solutions.This paper proposes a novel enhanced hybrid algorithm based on the basic HHO and CBO named Enhanced Harris Hawks Optimization Integrated with Coot Bird Optimization(EHHOCBO).EHHOCBO can provide higher-quality solutions for numerical optimization problems.It first embeds the leadership mechanism of CBO into the population initialization process of HHO.This way can take full advantage of the valuable solution information to provide a good foundation for the global search of the hybrid algorithm.Secondly,the Ensemble Mutation Strategy(EMS)is introduced to generate the mutant candidate positions for consideration,further improving the hybrid algorithm’s exploration trend and population diversity.To further reduce the likelihood of falling into the local optima and speed up the convergence,Refracted Opposition-Based Learning(ROBL)is adopted to update the current optimal solution in the swarm.Using 23 classical benchmark functions and the IEEE CEC2017 test suite,the performance of the proposed EHHOCBO is comprehensively evaluated and compared with eight other basic meta-heuristic algorithms and six improved variants.Experimental results show that EHHOCBO can achieve better solution accuracy,faster convergence speed,and a more robust ability to jump out of local optima than other advanced optimizers in most test cases.Finally,EHHOCBOis applied to address four engineering design problems.Our findings indicate that the proposed method also provides satisfactory performance regarding the convergence accuracy of the optimal global solution.

Progress in research on tumor microenvironment-based spatial omics technologies

Spatial omics technology integrates the concept of space into omics research and retains the spatial information of tissues or organs while obtaining molecular information.It is characterized by the ability to visualize changes in molecular information and yields intuitive and vivid visual results.Spatial omics technologies include spatial transcriptomics,spatial proteomics,spatial metabolomics,and other technologies,the most widely used of which are spatial transcriptomics and spatial proteomics.The tumor microenvironment refers to the surrounding microenvironment in which tumor cells exist,including the surrounding blood vessels,immune cells,fibroblasts,bone marrow-derived inflammatory cells,various signaling molecules,and extracellular matrix.A key issue in modern tumor biology is the application of spatial omics to the study of the tumor microenvironment,which can reveal problems that conventional research techniques cannot,potentially leading to the development of novel therapeutic agents for cancer.This paper summarizes the progress of research on spatial transcriptomics and spatial proteomics technologies for characterizing the tumor immune microenvironment.

A survey on computationally efficient neural architecture search

Neural architecture search(NAS)has become increasingly popular in the deep learning community recently,mainly because it can provide an opportunity to allow interested users without rich expertise to benefit from the success of deep neural networks(DNNs).However,NAS is still laborious and time-consuming because a large number of performance estimations are required during the search process of NAS,and training DNNs is computationally intensive.To solve this major limitation of NAS,improving the computational efficiency is essential in the design of NAS.However,a systematic overview of computationally efficient NAS(CE-NAS)methods still lacks.To fill this gap,we provide a comprehensive survey of the state-of-the-art on CE-NAS by categorizing the existing work into proxy-based and surrogate-assisted NAS methods,together with a thorough discussion of their design principles and a quantitative comparison of their performances and computational complexities.The remaining challenges and open research questions are also discussed,and promising research topics in this emerging field are suggested.

Sucrose-associated SnRK1a1-mediated phosphorylation of Opaque2 modulates endosperm filling in maize

During maize endosperm filling,sucrose not only serves as a source of carbon skeletons for storage-reserve synthesis but also acts as a stimulus to promote this process.However,the molecular mechanisms underlying sucrose and endosperm filling are poorly understood.In this study,we found that sucrose promotes the expression of endosperm-filling hub gene Opaque2(O2),coordinating with storage-reserve accumulation.We showed that the protein kinase SnRK1a1 can attenuate O2-mediated transactivation,but sucrose can release this suppression.Biochemical assays revealed that SnRK1a1 phosphorylates O2 at serine 41(S41),negatively affecting its protein stability and transactivation ability.We observed that mutation of SnRK1a1 results in larger seeds with increased kernel weight and storage reserves,while overexpression of SnRK1a1 causes the opposite effect.Overexpression of the native O2(O2-OE),phospho-dead(O2-SA),and phospho-mimetic(O2-SD)variants all increased 100-kernel weight.Although O2-SA seeds exhibit smaller kernel size,they have higher accumulation of starch and proteins,resulting in larger vitreous endosperm and increased test weight.O2-SD seeds display larger kernel size but unchanged levels of storage reserves and test weight.O2-OE seeds show elevated kernel dimensions and nutrient storage,like a mixture of O2-SA and O2-SD seeds.Collectively,our study discovers a novel regulatory mechanism of maize endosperm filling.Identification of S41 as a SnRK1-mediated phosphorylation site in O2 offers a potential engineering target for enhancing storage-reserve accumulation and yield in maize.

直接和间接消费所引起的中国城乡空气污染相关过早死亡不平等性

Household consumption in China is associated with substantial PM_(2.5)pollution,through activities directly(i.e.,fuel use)and/or indirectly(i.e.,consumption of goods and services)causing pollutant emissions.Urban and rural households exhibit different consumption preferences and living areas,thus their contributions to and suffering from air pollution could differ.Assessing this contrast is crucial for comprehending the environmental impacts of the nation’s ongoing urbanization process.Here we quantify Chinese urban and rural households’contributions to ambient PM_(2.5)pollution and the health risks they suffer from,by integrating economic,atmospheric,and health models and/or datasets.The national premature deaths related to long-term exposure to PM_(2.5)pollution contributed by total household consumption are estimated to be 1.1 million cases in 2015,among which 56%are urban households and 44%are rural households.For pollution contributed indirectly,urban households,especially in developed provinces,tend to bear lower mortality risks compared with the portions of deaths or pollution they contribute.The opposite results are true for direct pollution.With China’s rapid urbanization process,without adequate reduction in emission intensity,the increased indirect pollution-associated premature deaths could largely offset that avoided by reduced direct pollution,and the indirect pollution-associated urban–rural inequalities might become severer.Developing pollution mitigation strategies from both production and consumption sides could help with reducing pollution-related mortality and associated urban-rural inequality.

Inducing piezoelectricity in distorted rutile TiO_(2)for enhanced tetracycline hydrochloride degradation through photopiezocatalysis

Various material design strategies have been developed to enhance photocatalytic performance of TiO_(2).However,no report is available on applications of the photopiezocatalysis strategy on TiO_(2)due to its lack of piezoelectricity.Here we developed a low-temperature molten salt etching process to create rutile TiO_(2)nanoparticles by etching[MgO_(6)]octahedrons away from MgTiO_(3)by molten NH_(4)Cl,during which a lattice distortion occurred in TiO_(2).The lattice distortion broke the structure symmetry of rutile TiO_(2)and subsequently endowed these rutile TiO_(2)nanoparticles with an unusual piezoelectric response with the maximum effective piezoelectric coefficient(d_(33))of~41.6 pm/V,which had not previously been found in TiO_(2)photocatalysts.Thus,the photopiezocatalysis strategy was applied for the first time to enhance the photocatalytic performance of these TiO_(2)nanoparticles.The creation of lattice distortion to induce piezoelectricity could be extended to other photocatalysts that the photopiezocatalysis strategy has not been applied to and may generate novel functionalities for various technical applications.

Antimicrobial resistance characteristics and phylogenetic relationships of pleuromutilin-resistant Enterococcus isolates from different environmental samples along a laying hen production chain

Antimicrobial resistance in the laying hen production industry has become a serious public health problem.The antimicrobial resistance and phylogenetic relationships of the common conditional pathogen Enterococcus along the laying hen production chain have not been systematically clarified.105 Enterococcus isolates were obtained from 115 environmental samples (air,dust,feces,fies,sewage,and soil) collected along the laying hen production chain (breeding chicken,chick,young chicken,and commercial laying hen).These Enterococcus isolates exhibited resistance to some clinically relevant antibiotics,such as tetracycline (92.4%),streptomycin (92.4%),and erythromycin (91.4%),and all strains had multidrug resistance phenotypes.Whole genome sequencing characterized 29 acquired antibiotic resistance genes (ARGs) that conferred resistance to 11 classes of antibiotics in 51pleuromutilin-resistant Enterococcus isolates,and lsa(E),which mediates resistance to pleuromutilins,always co-occurred with lnu(B).Alignments with the Mobile Genetic Elements database identified four transposons (Tn554,Tn558,Tn6261,and Tn6674) with several ARGs(erm(A),ant(9)-la,fex(A),and optrA) that mediated resistance to many clinically important antibiotics.Moreover,we identified two new transposons that carried ARGs in the Tn554 family designated as Tn7508 and Tn7492.A complementary approach based on conventional multi-locus sequence typing and whole genome single nucleotide polymorphism analysis showed that phylogenetically related pleuromutilin-resistant Enterococcus isolates were widely distributed in various environments on different production farms.Our results indicate that environmental contamination by antimicrobial-resistant Enterococcus requires greater attention,and they highlight the risk of pleuromutilin-resistant Enterococcus and ARGs disseminating along the laying hen production chain,thereby warranting effective disinfection.

Mismatch analysis of all-fiber coherent beam combiners based on the self-imaging effect

All-fiber coherent beam combiners based on the self-imaging effect can achieve a near-perfect single laser beam,which can provide a promising way to overcome the power limitation of a single-fiber laser.One of the key points is combining efficiency,which is determined by various mismatches during fabrication.A theoretical model has been built,and the mismatch error is analyzed numerically for the first time.The mismatch errors have been numerically studied with the beam quality and combining efficiency being chosen as the evaluation criteria.The tolerance of each mismatch error for causing 1%loss is calculated to guide the design of the beam combiners.The simulation results are consistent with the experimental results,which show that the mismatch error of the square-core fiber is the main cause of the efficiency loss.The results can provide useful guidance for the fabrication of all-fiber coherent beam combiners.

Effect of post-heat treatment on Ti_(2)AlNb-based alloy fabricated by twin-wire alternating dual-electron beam additive manufacturing technology

Thanks to its excellent high-temperature performance and moderate density,Ti_(2) AlNb-based alloy is con-sidered to be a new generation of high-temperature structural material in the aerospace field.However,its application is restricted currently due to the limitations of traditional processing methods.Recently,our group first successfully prepared this alloy with an unconventional approach named wire-based in-situ additive manufacturing(AM)technology,and great mechanical performance has been obtained.The unbalanced thermal process of AM easily causes inconsistent or undesired microstructures,as well as mechanical properties.Therefore,in this study,we further carried out post-heat treatment research on the as-printed sample so as to optimize its mechanical performance.Results show that theα2-phase will precipitate from the as-deposited samples(B2/β+O)after solution treatment(ST),while all precipitates were dissolved to the B2/β-matrix when the solution temperature was 1100℃.The aging treatment(AT)promoted a great number of O-phases precipitated and led to an increase in its proportion.With the increase in aging temperature,the tensile strength decreased(995 to 821 MPa)gradually coupling the increase of fracture strain(1.65%to 2.12%),while the aging duration time did not show an obvious ef-fect on its performance.In addition,after proper heat treatment,the high temperature(650℃)tensile strength of the samples was as high as 818 and 792 MPa.This research not only promotes the develop-ment of Ti_(2) AlNb-based alloy fabricated through in-situ AM,but also facilitates its further application in the aerospace field.

Recent advances of magnesium hydride as an energy storage material

Energy storage is the key for large-scale application of renewable energy,however,massive efficient en-ergy storage is very challenging.Magnesium hydride(MgH_(2))offers a wide range of potential applications as an energy carrier due to its advantages of low cost,abundant supplies,and high energy storage capac-ity.However,the practical application of MgH_(2) for energy storage is still impeded by its sluggish kinetics,poor cycling stability,etc.Herein,we provide an overview of recent advances of MgH_(2) for enhancing the hydrogen storage,lithium-ion storage,and heat storage performances.For hydrogen storage,a particular emphasis was put on altering the kinetics and thermodynamics of MgH_(2) via catalyzing,alloying,nano-sizing,and compositing.Modifications to MgH_(2) as a battery anode material mainly focus on the effect of additives,electrolytes,and structure configurations.Prototype heat storage apparatus was proposed based on MgH_(2) and coupled with other materials or systems to improve the heat storage and economic efficiency.Besides,prospects of MgH_(2) in these fields are discussed.This review would stimulate more insightful and pioneering research for the design and preparation of MgH_(2) with excellent energy storage performances.

Exploring the abundance and influencing factors of antimicrobial resistance genes in manure plasmidome from swine farms

Plasmids play a critical role in the dissemination of antimicrobial resistance genes(ARGs),however,a systematical understanding of ARGs originated from plasmids in swine production is currently lacking.Herein,quantitative polymerase chain reaction was applied to determine the prevalence of ten ARGs and the class1 integron gene intI1 of plasmid source in swinemanure from 44 farms in Sichuan,Hubei and Hebei provinces,China.All assayed ARGs were observed in plasmid DNA samples,and the average absolute abundance of aac(6’)-Ib-cr,blaNDM,blaCTX-M,optrA,ermB,floR,mcr-1,qnrS,tetM,sul1 and intI1 were 7.09,2.90,4.67,6.62,7.55,7.14,4.08,4.85,7.16,7.11 and 8.07 of 10 log copies/gram,respectively.IntI1 showed a high correlation(r>0.8,P<0.01)with the abundance of aac(6’)-Ib-cr and sul1 in swine manure.Moreover,the farm scale(i.e.,herd population)and geographical location were not found to be critical factors influencing the absolute abundance of ARGs of plasmid DNA in swine farms.However,the concentrations of florfenicol,Cu,Zn,Fe,total phosphorus(TP)and total potassium(TK)demonstrated a significant correlation with the abundance of several ARGs.Particularly,Cu and Zn had high correlations with optrA and blaCTX-M,respectively.Our results demonstrated that antibiotics,heavy metals and environmental nutrients are likely jointly contributing to the long-term persistence of ARGs in swine production.This study provides insights into the abundance and influencing factors of ARGs from swine manure,which is of significance for assessing and reducing the public health risks in livestock production.

Highly selective photocatalytic CO_(2) reduction to ethylene in pure water by Nb_(2)O_(5) nanoparticles with enriched surface –OH groups under simulated solar illumination

Photocatalytic CO_(2) reduction to valuable chemical compounds could be a promising approach for carbon-neutral practice.In this work,a simple and robust thermal decomposition process was developed with ammonium carbonate((NH4)2CO3)as both precipitation agent and sacrificial template to produce fine Nb_(2)O_(5) nanoparticles with the rich existence of surface hydroxyl(–OH)groups.It was found by density functional theory(DFT)calculations and experiments that the rich existence of the surface–OH groups enhanced the adsorption of both reactants(CO_(2) and H_(2)O molecules)for the photocatalytic CO_(2) reduction on these fine Nb_(2)O_(5) nanoparticles,and the highly selective conversion of CO_(2) to the high-value chemical compound of ethylene(C_(2)H_(4),~68μmol·g^(−1)·h^(−1) with~100%product selectivity)was achieved under simulated solar illumination without usage of any sacrificial agents or noble metal cocatalysts.This synthesis process may also be readily applied as a surface engineering method to enrich the existence of the surface–OH groups on various metal oxide-based photocatalysts for a broad range of technical applications.

Epigenetic regulation of mesenchymal stem cell aging through histone modifications

Stem cell senescence and exhaustion,a hallmark of aging,lead to declines in tissue repair and regeneration in aged individuals.Emerging evidence has revealed that epigenetic regulation plays critical roles in the self-renew,lineage-commitment,survival,and function of stem cells.Moreover,epigenetic alterations are considered important drivers of stem cell dysfunction during aging.In this review,we focused on current knowledge of the histone modifications in the aging of mesenchymal stem cells(MSCs).The aberrant epigenetic modifications on histones,including methylation and acetylation,have been found in aging MSCs.By disturbing the expression of specific genes,these epigenetic modifications affect the self-renew,survival,and differentiation of MSCs.A set of epigenetic enzymes that write or erase these modifications are critical in regulating the aging of MSCs.Furthermore,we discussed the rejuvenation strategies based on epigenetics to prevent stem cell aging and/or rejuvenate senescent MSCs.

Radial electromagnetic type unbalance vibration self-recovery regulation system for high-end grinding machine spindles

Modern rotating machines,which are represented by high-end grinding machines,have developed toward high precision,intelligence,and high durability in recent years.As the core components of grinding machine spindles,grinding wheels greatly affect the vibration level during operation.The unbalance vibration self-recovery regulation(UVSRR)system is proposed to suppress the vibration of grinding wheels during workpiece processing,eliminating or minimizing the imbalance.First,technical principles and the system composition are introduced.Second,the balancing actuator in the UVSRR system is analyzed in detail.The advanced nature of the improved structure is presented through structure introduction and advantage analysis.The performance of the balancing actuator is mutually verified by the theoretical calculation of torque and software simulation.Results show that the self-locking torque satisfies the actual demand,and the driving torque is increased by 1.73 times compared with the traditional structure.Finally,the engineering application value of the UVSRR system is verified by laboratory performance comparison and actual factory application.The balancing speed and effect of the UVSRR system are better than those of an international mainstream product and,the quality of the workpieces machined in the factory improved by 40%.

Climate change in the Hongliujing area of Lop Nur over the past 200 years revealed by the stable oxygen isotopes of Tamarix cones

The layers of Tamarix cones within sedimentary deposits in arid regions have significant chronological and paleoenvironmental implications.Here,we compare the δ^(18)O values of Tamarix cones in the Hongliujing area of Lop Nur with meteorological data for the Ruoqiang meteorological station for 1960-2019 AD.Linear regression analysis was used to reconstruct the average temperature for April and the precipitation for November in the Hongliujing area over the past 200 years.The results showed that the δ^(18)O values were significantly negatively correlated with the temperature for February,April,May,August,December,and with the annual mean temperature;significantly negatively correlated with the precipitation for February and April;significantly negatively correlated with the sunshine hours for March and May;significantly positively correlated with the sunshine hours for February,July,August,October,and December,and with the annual mean values;and significantly correlated with the relative humidity for April,July,August,September,October,and November,and with the annual mean values.Based on the δ^(18)O record of the past 200 years,the Hongliujing area experienced two warm-wet periods(1874-1932 and 2004-2019 AD)and two cold-dry periods(1832–1873 and 1933-2003 AD).Thus,the climate was characterized by alternating warm-wet and cold-dry conditions.Wavelet analysis revealed three main cycles:45 years,29 years,and 14 years.

Crustal velocity structure of the Northwest Sub-basin of the South China Sea based on seismic data reprocessing

The deep crustal structure of the Northwest Sub-basin(NWSB)of the South China Sea(SCS)is of great importance for understanding the tectonic nature of the continent-ocean transition(COT)and magmatism in this oceanic basin.The 2-D wide-angle reflection/refraction seismic profile OBS2006-2 is almost parallel to the extinct spreading ridge(ESR)of the NWSB.In addition to the original data,we added the data of two reprocessed OBS stations,and carried out seismic phase re-picking and travel-time imaging to obtain the crustal velocity structure along this profile.Resolution tests demonstrate that the newly acquired velocity structure is more reliable than the prior interpretation.The depth of the Moho(23.5–11.8 km)and crustal thickness(20.5–6.5 km)systematically changes from continental crust of the Xisha Block to the oceanic crust within the NWSB.The COT zone has a width of^20 km and the depth of the Moho decreases from 15.0 to 11.0 km,corresponding to a^4 km decrease in crustal thickness(6–10 km).A high velocity layer(HVL,7.2–7.4 km s–1)exists at the bottom of the crust at the location where the sharp lateral transition of the continental crust to the oceanic crust occurs.Age dating shows that the Doublepeak Seamount was formed at^23 Ma,after the cessation of the NWSB seafloor spreading(~32–25 Ma).The crust beneath the Double-peak Seamount is oceanic with a thickness of 9 km.We infer that this oceanic crust was formed by magmatic upwelling and decompression melting along a pre-existing zone of weakness.