A novel approach of decorating graphene surface with graphene quantum dots(abbreviated as GQDs@Gr)was presented to achieve superior tribological properties in Gr/Cu composites.The prepared GQDs@Gr hybrid reinforcement...A novel approach of decorating graphene surface with graphene quantum dots(abbreviated as GQDs@Gr)was presented to achieve superior tribological properties in Gr/Cu composites.The prepared GQDs@Gr hybrid reinforcement possessed superior dispersion and had achieved strong interface bonding with Cu matrix.GQDs@Gr/Cu composite showed a good combination of wear resistance and electrical conductivity due to the synergistic effect of GQDs and Gr.Specifically,the coefficient of friction(COF)was reduced to 0.3,the wear rate(WR)was 2.13×10^(-5) mm^(3)·N^(−1)·m^(−1)(only a quarter of pure copper),and maintained the electrical conductivity of 96.5%IACS(international annealed copper standard).As a result,delamination,fracture,and plow furrows on the wear surface of Gr/Cu composite indicate that fatigue and abrasive adhesive wear are the main wear mechanisms.Wear surface lubrication film and strong interface bonding ensure better comprehensive performance of GQDs@Gr/Cu composite.展开更多
Based on the strength reduction method and strain-softening model,a method for progressive failure analysis of strain-softening slopes was presented in this paper.The mutation is more pronounced in strain-softening an...Based on the strength reduction method and strain-softening model,a method for progressive failure analysis of strain-softening slopes was presented in this paper.The mutation is more pronounced in strain-softening analysis,and the mutation of displacement at slope crest was taken as critical failure criterion.An engineering example was provided to demonstrate the validity of the present method.This method was applied to a cut slope in an industry site.The results are as follows:(1) The factor of safety and the critical slip surface obtained by the present method are between those by peak and residual strength.The analysis with peak strength would lead to non-conservative results,but that with residual strength tends to be overly conservative.(2) The thickness of the shear zone considering strain-softening behaviour is narrower than that with non-softening analysis.(3) The failure of slope is the process of the initiation,propagation and connection of potential failure surface.The strength parameters are mobilized to a non-uniform degree while progressive failure occurs in the slope.(4) The factor of safety increases with the increase of residual shear strain threshold and elastic modulus.The failure mode of slope changes from shallow slip to deep slip.Poisson's ratio and dilation angle have little effect on the results.展开更多
Pure WC-6%Co nanosized composite powders were synthesized via a low-temperature method.The effects of carbon source on microstructure characteristic of composite powders were investigated,and the effects of heat-treat...Pure WC-6%Co nanosized composite powders were synthesized via a low-temperature method.The effects of carbon source on microstructure characteristic of composite powders were investigated,and the effects of heat-treatment parameter on carbon content of composite powders were also discussed.The results of SEM and XRD revealed that the carbon decomposing from glucose was more active than carbon black.Therefore,WC-Co nanosized composite powders could be synthesized at 900°C for 1 h under a hydrogen atmosphere.The individual WC grains were bonded together into a long strip under the action of cobalt.The results of carbon analysis revealed that the total carbon content decreased with the increase of the temperature in the range of 800-1000°C.Moreover,the total carbon content and the compounded carbon increased with the increase of the flow rate of H2 in the range of 1.1-1.9 m3/h.展开更多
To address the issues of reduced graphene oxide(RGO) dispersion in copper(Cu) matrix and interface bonding between RGO and Cu, an electrostatic adsorption method with interface transition phase design was employed to ...To address the issues of reduced graphene oxide(RGO) dispersion in copper(Cu) matrix and interface bonding between RGO and Cu, an electrostatic adsorption method with interface transition phase design was employed to prepare the RGO/Cu based composites. Cu-Ti alloy powder was employed to improve the combination by forming carbides at the RGO-Cu interface. It was noted that the mechanical property of 0.3 wt.%RGO/Cu-Ti composite was increased by 60% compared with that of the matrix. Strengthening mechanism analysis suggested that the enhancement of the mechanical property was ascribed to the load transfer and second phase strengthening which were from the improved dispersion of RGO and the in-situ formed titanium carbide phase.展开更多
To investigate the microwave effect on the WC–Co alloys,WC–8 wt%Co alloy was fabricated by microwave sintering(MWS)in this paper.The results show that decarburization layer forms on the surface of the microwave-sint...To investigate the microwave effect on the WC–Co alloys,WC–8 wt%Co alloy was fabricated by microwave sintering(MWS)in this paper.The results show that decarburization layer forms on the surface of the microwave-sintered samples.WC grain coarsening in the core area is strongly suppressed by the decarburization effect.In addition,the microstructure of the MWS-fabri-cated alloy was compared to that of the alloy sintered by vacuum sintering(VS).Microstructural investigations by transmission electron microscopy(TEM)and energy dis-persive spectroscopy(EDS)show that more tungsten(29.50 wt%)is dissolved in the cobalt binder phase in microwave-sintered alloy than that in the vacuum-sintered samples.Finally,the formation mechanism of the surface layer by skin effect was discussed.展开更多
While the present structural integrity evaluation method is based on the philosophy of assumed similitude, Fatigue and Damage Tolerance(F&DT) evaluations for next generation of air-vehicles require high-fidelity p...While the present structural integrity evaluation method is based on the philosophy of assumed similitude, Fatigue and Damage Tolerance(F&DT) evaluations for next generation of air-vehicles require high-fidelity physical models within cyberspace. To serve the needs of F&DT evaluation in digital twin paradigm, a fatigue damage-cumulative model within peridynamic framework is proposed in this paper. Based on the concept of fatigue element block and damage accumulation law in form of Coffin-Manson relationship, the proposed model applies to both fatigue crack initiation and fatigue crack growth;fatigue crack growth rates under constant-amplitude and simple variable-amplitude block loading cases can be well predicted for three common structural materials without inputs of Paris law parameters. Additionally, the proposed model can also be easily extended to a probabilistic version;for verification, multiple-site-damage problems are simulated and the statistic nature of fatigue process in experiments can be well captured. In the end, main features of the proposed model are summarized, and distinctions from the other models are discussed. There may be a potential for the peridynamic damage-cumulative model proposed in this work to numerically predict fatigue problems in digital twin paradigm for future generations of aerospace vehicles.展开更多
This paper presents an incremental cutting method for evaluating the longitudinal residual stresses in a butt welded thin plate via combining the traditional residual stress measurement methods and the advanced optica...This paper presents an incremental cutting method for evaluating the longitudinal residual stresses in a butt welded thin plate via combining the traditional residual stress measurement methods and the advanced optical technique.The proposed approach,which can be called digital image correlation（DIC）-aided slitting technique,introduces a successive extension slot to a specimen and employs the DIC technique to measure the released displacement profiles of the cutting sections after each cutting increment.Then the displacement profiles are used to directly calculate the residual stress distributions up to the slot tip and hence,a stress distribution can be obtained after a cutting increment.Finally,all of the stress distributions are averaged to ultimately determine the original residual stress field.This method does not include any complex experimental operations or tedious derivation,and the resolution of stress variation is greatly improved by the continuous measurement of the released displacements.The presented method has been preliminarily verified by a specimen with residual stress introduced by a four-point bending test.The results show that residual stresses determined by the DIC-aided slitting technique agree well with those from finite element（FE） prediction.The residual stress in a friction stir welded aluminum specimen obtained by the presented technique is also consistent with the evaluations given by X-ray diffraction.Furthermore,the residual stresses obtained by the DIC-aided slitting technique demonstrate higher accuracy and stability than the evaluations derived by the DIC-aided contour method.展开更多
In order to uniformly disperse the ceramic reinforcements synthesized in-situ in the copper matrix composites,this study used Carbon Polymer Dot(CPD)as the carbon source and Cu–1.0%Ti alloy powder as the matrix for s...In order to uniformly disperse the ceramic reinforcements synthesized in-situ in the copper matrix composites,this study used Carbon Polymer Dot(CPD)as the carbon source and Cu–1.0%Ti alloy powder as the matrix for supplying Ti source to prepare in-situ synthesized TiC/Cu composites.The results show that TiC nano-precipitates,having the similar particle sizes with the CPD,form at the grains interior and grain boundaries,and maintain a uniform distribution state.Compared with the matrix,0.3 wt%CPD/Cu composite displays the best strengthplastic compatibility,the ultimate tensile strength achieves 385 MPa accompanied with a corresponding elongation of 21%,owing to the dislocation hindrance caused by nano-carbide and excellent interface bonding between nano TiC and the Cu matrix.The density function theory calculation supports our experimental results by showing a tighter and stronger interface contact.This work presents a new approach for studying in-situ carbide precipitates.展开更多
Isotropic Sm-Co nanoparticle powders with high coercivity were prepared by high-energy ball milling followed by optimal annealing at different temperatures.The covercivity increased monotonically with increasing of th...Isotropic Sm-Co nanoparticle powders with high coercivity were prepared by high-energy ball milling followed by optimal annealing at different temperatures.The covercivity increased monotonically with increasing of the annealing temperature and a highest coercivity of 31.2 kOe was obtained.The sample with an optimal energy product of 17.0 MGOe still had a coercivity of 18.2 kOe.The evolution of phase,particle size,mechanism of coercivity and other related magnetic properties were analyzed.The excellent performance is attributed to nanoscale size grains below 15 nm and good exchange coupling between nanoparticles.展开更多
The configuration and quality of reinforcements, as well as the robustness of interfacial bonding,holding a critical significance in determining the concurrence between electrical conductivity and mechanical strength ...The configuration and quality of reinforcements, as well as the robustness of interfacial bonding,holding a critical significance in determining the concurrence between electrical conductivity and mechanical strength in metal matrix composites. In this study, citric acid was employed as the precursor for synthesizing multiscale carbon nanomaterials(graphene quantum dots and graphene, abbreviated as GQDs and GN). The GQDs@GN/Cu composites were fabricated through a segmented ball milling process in conjunction with subsequent spark plasma sintering(SPS). The intragranular GQDs and intergranular GQDs@GN had synergistically reinforced Cu composites through Orowan strengthening, load transfer strengthening and refinement strengthening. Furthermore,the robust interface bonding between GQDs@GN and Cu effectively mitigated interfacial impedance stemming from electron-boundary scattering. The yield strength and ultimate tensile strength of the GQDs@GN/Cu composites were recorded as 270 and 314 MPa, respectively, representing an improvement of 92 and 28% over pure Cu, while maintaining electrical conductivity at a level comparable to that of pure Cu. This study advances the understanding of the possibility of realizing a synergistic compatibility between electrical conductivity and mechanical strength in Cu composites.展开更多
Strengthening interface bonding between boron nitride nanosheets(BNNS)and copper matrix is an essential prerequisite for exploiting a new generation of copper matrix composites(CMCs)with high strength and wear resista...Strengthening interface bonding between boron nitride nanosheets(BNNS)and copper matrix is an essential prerequisite for exploiting a new generation of copper matrix composites(CMCs)with high strength and wear resistance.Herein,BNNS/Cu composites were fabricated by the powder metallurgy route,matrix-alloying(adding 1.0 wt%Ti)strategy was adopted to improve the interfacial wettability and strengthen interface adhesion.A typical"sandwich"-like multiply interface structure involving TiN transition layers,BNNS and Cu matrix had been well constructed through the rational heat treatment(900℃ for 120 min).Additionally,nano-sized TiB whisker was in situ formed in the vicinity of the interface,it had linked the BNNS-Cu-TiN multiply interface,which played a role of"threading the needle"and significantly strengthened the multi-interfaces bonding.This specific interface structure was finely characterized,and the formation mechanism of solid-state interfacial reaction feature was proposed.The results demonstrated that the ultimate tensile strength(UTS)of BNNS/Cu-(Ti)-900℃ increased from 248 to 530 MPa(increased by 114%),and the coefficient of friction(COF)decreased from 0.51 to 0.28 than pure Cu.This work highlights the importance of interface configuration design,which contributes to the development of CMCs with prominent comprehensive properties.展开更多
In this study,wild eggplant germplasm No.M239,which is highly susceptible to Verticillium wilt,was used as the experimental material.The physiological and biochemical indices(SOD,PAL,MDA and soluble protein)of M239 ro...In this study,wild eggplant germplasm No.M239,which is highly susceptible to Verticillium wilt,was used as the experimental material.The physiological and biochemical indices(SOD,PAL,MDA and soluble protein)of M239 roots were measured at different times(0,12,24,36,48,60 and 72 h)post inoculation with Verticillium dahliae,and the key time points for the M239 response to Verticillium wilt infection were screened.Then,RNA-Seq technology was used to screen the differentially expressed genes(DEGs)in M239 roots at 0,12 and 48 h post-inoculation(hpi).The transcriptional results of M239 were also compared with those resistance genes from some reported wild relative Solanum species(S.sisymbriifolium and S.aculeatissimum).Then some DEGs were chosen for validation by qRT–PCR.The results showed that 12 and 48 hpi were the turning points in the changes in all physiological and biochemical indices.A total of 6,783 DEGs were identified by RNA-Seq,including 6,141 DEGs(3,046 upregulated and 3,095 downregulated)at the M_12 h vs.M_0 h,1,903 DEGs(792 upregulated and 1,111 downregulated)at M_48 h vs.M_12 h,and 1,261 DEGs that appeared simultaneously in both stages.KEGG enrichment analysis showed that there were 5 metabolic pathways enriched from DEGs,which were mostly related to primary metabolism,such as glycolysis,amino acid and ribosome biogenesis.Compared with the NCBI non-redundant protein(NR)database,one Ve2 homologous gene and 8 PR protein-related genes were screened.Transcription factor analysis showed that there were a large number of DEGs,such as MYB,AP2-EREBP,bHLH,NAC and Orphans in the two stages.Compared with the reported Verticillium wilt-resistant wild eggplant species,it was found that there were fewer genes and enriched metabolic pathways in the M239 response to Verticillium wilt infection,and it also lacked the response of some known key resistance genes.These results proved that the above resistance genes and metabolic pathways played a key role in the wild eggplant response to V.dahliae infection.展开更多
Taking the wireless enamel(wireless enamel refers to make enamel works without filigree)production technique in jewelry practice course as the research object,combined with years of enamel teaching experience in the G...Taking the wireless enamel(wireless enamel refers to make enamel works without filigree)production technique in jewelry practice course as the research object,combined with years of enamel teaching experience in the Gemmological Institute of China University of Geosciences(Wuhan),this study expounds the theoretical class,design preparation,creative idea and technique practice application from the course teaching objectives and the implementation,which also emphasizes the practical improvability of students’design practice ability and innovative thinking ability.During the period,it focuses on the core processes,such as wireless enamel glaze method,object correction,firing time,composite application and system integration,to help students solve the key and difficult problems in the wireless enamel firing process.展开更多
The realization of high-quality(Q)resonators regardless of the underpinning material platforms has been a ceaseless pursuit,because the high-Q resonators provide an extreme environment for confining light to enable ob...The realization of high-quality(Q)resonators regardless of the underpinning material platforms has been a ceaseless pursuit,because the high-Q resonators provide an extreme environment for confining light to enable observations of many nonlinear optical phenomenon with high efficiencies.Here,photonic microresonators with a mean Q factor of 6.75×10^(6)were demonstrated on a 4H-silicon-carbide-on-insulator(4H-SiCOI)platform,as determined by a statistical analysis of tens of resonances.Using these devices,broadband frequency conversions,including second-,third-,and fourth-harmonic generations have been observed.Cascaded Raman lasing has also been demonstrated in our SiC microresonator for the first time,to the best of our knowledge.Meanwhile,by engineering the dispersion properties of the SiC microresonator,we have achieved broadband Kerr frequency combs covering from 1300 to 1700nm.Our demonstration represents a significant milestone in the development of SiC photonic integrated devices.展开更多
The fast-developing synthetic biology(SB)has provided many genetic tools to reprogram and engineer cells for improved performance,novel functions,and diverse applications.Such cell engineering resources can play a cri...The fast-developing synthetic biology(SB)has provided many genetic tools to reprogram and engineer cells for improved performance,novel functions,and diverse applications.Such cell engineering resources can play a critical role in the research and development of novel therapeutics.However,there are certain limitations and challenges in applying genetically engineered cells in clinical practice.This literature review updates the recent advances in biomedical applications,including diagnosis,treatment,and drug development,of SB-inspired cell engineering.It describes technologies and relevant examples in a clinical and experimental setup that may significantly impact the biomedicine field.At last,this review concludes the results with future directions to optimize the performances of synthetic gene circuits to regulate the therapeutic activities of cell-based tools in specific diseases.展开更多
In view of wide applications of structured light fields and plasmonic vortices,we propose the concept of compound plasmonic vortex and design several structured plasmonic vortex generators.This kind of structured plas...In view of wide applications of structured light fields and plasmonic vortices,we propose the concept of compound plasmonic vortex and design several structured plasmonic vortex generators.This kind of structured plasmonic vortex generators consists of multiple spiral nanoslits and they can generate two or more concentric plasmonic vortices.Different from Laguerre-Gaussian beam,the topological charge of the plasmonic vortex in different region is different.Theoretical analysis lays the basis for the design of radially structured plasmonic vortex generators and numerical simulations for several examples confirm the effectiveness of the design principle.The discussions about the interference of vortex fields definite the generation condition for the structured vortex.This work provides a design methodology for generating new vortices using spiral nanoslits and the advanced radially structured plasmonic vortices is helpful for broadening the applications of vortex fields.展开更多
In this study,glucose and NH4F were utilized as sources of carbon and fluorine,respectively,for the synthesis of LiMn_(0.6)Fe_(0.4)PO_(4)(LMFP)nanoscales.These nanoscales were subsequently modified with varying levels...In this study,glucose and NH4F were utilized as sources of carbon and fluorine,respectively,for the synthesis of LiMn_(0.6)Fe_(0.4)PO_(4)(LMFP)nanoscales.These nanoscales were subsequently modified with varying levels of fluorine-doped carbon through co-precipitation and mechanical ball milling processes.The LMFP,incorporating carbon and varying levels of fluoride ions,exhibit higher specific discharge capacities at 0.2 Cand electrochemical characteristics compared to the original LMFP coated solely with carbon.The inclusion of fluorine-doped carbon in the composite material creates numerous pathways for expeditious electron transfer.Moreover,the partial formation of metal fluoride at the interface between the surface of LMFP and the layer of carbon coating doped with fluorine enhances the reduction in the charge-transfer resistance.The modified ferromanganese phosphate cathode material reveals an outstanding discharge capacity displaying a reversible discharge specific capacity value of 131.73 mA h g^(−1)at 10C and 154.6 mA h g^(−1)at 0.2C,due to its unique structure.展开更多
Tetracycline repressor(TetR)family regulators(TFRs)are the largest group of DNA-binding transcription factors and are widely distributed in bacteria and archaea.TFRs play vital roles in controlling the expression of v...Tetracycline repressor(TetR)family regulators(TFRs)are the largest group of DNA-binding transcription factors and are widely distributed in bacteria and archaea.TFRs play vital roles in controlling the expression of various genes and regulating diverse physiological processes.Recently,a TFR protein Pseudomonas virulence regulator A(PvrA),was identified from Pseudomonas aeruginosa as the transcriptional activator of genes involved in fatty acid utilization and bacterial virulence.Here,we show that PvrA can simultaneously bind to multiple pseudo-palindromic sites and upregulate the expression levels of target genes.Cryo-electron microscopy(cryo-EM)analysis indicates the simultaneous DNA recognition mechanism of PvrA and suggests that the bound DNA fragments consist of a distorted B-DNA double helix.The crystal structure and functional analysis of PvrA reveal a hinge region that secures the correct domain motion for recognition of the promiscuous promoter.Additionally,our results showed that mutations disrupting the regulatory hinge region have differential effects on biofilm formation and pyocyanin biosynthesis,resulting in attenuated bacterial virulence.Collectively,these findings will improve the understanding of the relationship between the structure and function of the TetR family and provide new insights into the mechanism of regulation of P.aeruginosa virulence.展开更多
Marine dissolved organic matter (DOM) represents the largest carbon reservoir (~662 Pg carbon;Hansell, 2013). DOM in the ocean could be introduced from rivers, marine aerosols, and adjacent continental shelves, even p...Marine dissolved organic matter (DOM) represents the largest carbon reservoir (~662 Pg carbon;Hansell, 2013). DOM in the ocean could be introduced from rivers, marine aerosols, and adjacent continental shelves, even produced, and transformed by physical processes (such as desorption and transfer), as well as microbial processes. A significant amount of DOM resists quick degradation and is classified as refractory DOM (RDOM) based on its reactivity and longevity (Hansell, 2013).展开更多
Metallic phthalocyanines are promising electrocatalysts for CO_(2) reduction reaction(CO_(2)RR).However,their catalytic activity and stability(especially under high potential)are still unsatisfactory.Herein,we synthes...Metallic phthalocyanines are promising electrocatalysts for CO_(2) reduction reaction(CO_(2)RR).However,their catalytic activity and stability(especially under high potential)are still unsatisfactory.Herein,we synthesized a covalent organic polymer(COP-CoPc)by introducing charge-switchable viologen ligands into cobalt phthalocyanine(CoPc).The COP-CoPc exhibits great activity for CO_(2)RR,including a high Faradaic efficiency over a wide potential window and the highest CO partial current density among all ligand-tuned phthalocyanine catalysts reported in the H-type cell.Particularly,COP-CoPc also shows great potential for practical applications,for example,a FECO of>95%is realized at a large current density of 150 mA/cm^(2) in a two-electrode membrane electrode assembly reactor.Ex situ and in situ X-ray absorption fine structure spectroscopy measurements and theory calculations reveal that when the charge-switchable viologen ligands switch to neutral-state ones,they can act as electron donors to enrich the electron density of Co centers in COP-CoPc and enhance the desorption of*CO,thus improving the CO selectivity.Moreover,the excellent reversible redox capability of viologen ligands and the increased Co–N bonding strength in the Co–N4 sites enable COP-CoPc to possess outstanding stability under elevated potentials and currents,enriching the knowledge of charge-switchable ligands tailored CO_(2)RR performance.展开更多
基金supported by Yunnan Fundamental Research Projects(No.202401CF070085)Yunnan Engineering Research Projects(No.2023-XMDJ-00617273)+1 种基金Industrial Support Plan Project of Gansu Provincial Education Department(No.2024CYZC-22)the National Natural Science Foundation of China(No.52064032).
文摘A novel approach of decorating graphene surface with graphene quantum dots(abbreviated as GQDs@Gr)was presented to achieve superior tribological properties in Gr/Cu composites.The prepared GQDs@Gr hybrid reinforcement possessed superior dispersion and had achieved strong interface bonding with Cu matrix.GQDs@Gr/Cu composite showed a good combination of wear resistance and electrical conductivity due to the synergistic effect of GQDs and Gr.Specifically,the coefficient of friction(COF)was reduced to 0.3,the wear rate(WR)was 2.13×10^(-5) mm^(3)·N^(−1)·m^(−1)(only a quarter of pure copper),and maintained the electrical conductivity of 96.5%IACS(international annealed copper standard).As a result,delamination,fracture,and plow furrows on the wear surface of Gr/Cu composite indicate that fatigue and abrasive adhesive wear are the main wear mechanisms.Wear surface lubrication film and strong interface bonding ensure better comprehensive performance of GQDs@Gr/Cu composite.
基金Project supported by the National Natural Science Foundation of China (No. 10972238)the Scholarship Award for Excellent Doctoral Student Granted by Ministry of Educationthe Transportation Science and Technology Projects of Hunan Province (No. 201003),China
文摘Based on the strength reduction method and strain-softening model,a method for progressive failure analysis of strain-softening slopes was presented in this paper.The mutation is more pronounced in strain-softening analysis,and the mutation of displacement at slope crest was taken as critical failure criterion.An engineering example was provided to demonstrate the validity of the present method.This method was applied to a cut slope in an industry site.The results are as follows:(1) The factor of safety and the critical slip surface obtained by the present method are between those by peak and residual strength.The analysis with peak strength would lead to non-conservative results,but that with residual strength tends to be overly conservative.(2) The thickness of the shear zone considering strain-softening behaviour is narrower than that with non-softening analysis.(3) The failure of slope is the process of the initiation,propagation and connection of potential failure surface.The strength parameters are mobilized to a non-uniform degree while progressive failure occurs in the slope.(4) The factor of safety increases with the increase of residual shear strain threshold and elastic modulus.The failure mode of slope changes from shallow slip to deep slip.Poisson's ratio and dilation angle have little effect on the results.
基金Project(51274107)supported by the National Natural Science Foundation of ChinaProject(2015FB127)supported by the Yunnan Natural Science Foundation,ChinaProject(2016P20151130003)supported by Analysis Foundation of Kunming University of Science and Technology,China
文摘Pure WC-6%Co nanosized composite powders were synthesized via a low-temperature method.The effects of carbon source on microstructure characteristic of composite powders were investigated,and the effects of heat-treatment parameter on carbon content of composite powders were also discussed.The results of SEM and XRD revealed that the carbon decomposing from glucose was more active than carbon black.Therefore,WC-Co nanosized composite powders could be synthesized at 900°C for 1 h under a hydrogen atmosphere.The individual WC grains were bonded together into a long strip under the action of cobalt.The results of carbon analysis revealed that the total carbon content decreased with the increase of the temperature in the range of 800-1000°C.Moreover,the total carbon content and the compounded carbon increased with the increase of the flow rate of H2 in the range of 1.1-1.9 m3/h.
基金Project(2019ZE001)supported by the Yunnan Science and Technology Major Project,ChinaProject(YNWR-QNBJ-2018-005)supported by Yunnan Ten Thousand Talents Plan Young & Elite Talents Project,China。
文摘To address the issues of reduced graphene oxide(RGO) dispersion in copper(Cu) matrix and interface bonding between RGO and Cu, an electrostatic adsorption method with interface transition phase design was employed to prepare the RGO/Cu based composites. Cu-Ti alloy powder was employed to improve the combination by forming carbides at the RGO-Cu interface. It was noted that the mechanical property of 0.3 wt.%RGO/Cu-Ti composite was increased by 60% compared with that of the matrix. Strengthening mechanism analysis suggested that the enhancement of the mechanical property was ascribed to the load transfer and second phase strengthening which were from the improved dispersion of RGO and the in-situ formed titanium carbide phase.
基金the National Natural Science Foundation of China(No.51274107)。
文摘To investigate the microwave effect on the WC–Co alloys,WC–8 wt%Co alloy was fabricated by microwave sintering(MWS)in this paper.The results show that decarburization layer forms on the surface of the microwave-sintered samples.WC grain coarsening in the core area is strongly suppressed by the decarburization effect.In addition,the microstructure of the MWS-fabri-cated alloy was compared to that of the alloy sintered by vacuum sintering(VS).Microstructural investigations by transmission electron microscopy(TEM)and energy dis-persive spectroscopy(EDS)show that more tungsten(29.50 wt%)is dissolved in the cobalt binder phase in microwave-sintered alloy than that in the vacuum-sintered samples.Finally,the formation mechanism of the surface layer by skin effect was discussed.
基金supported by the National Natural Science Foundation of China (No. 11672012)。
文摘While the present structural integrity evaluation method is based on the philosophy of assumed similitude, Fatigue and Damage Tolerance(F&DT) evaluations for next generation of air-vehicles require high-fidelity physical models within cyberspace. To serve the needs of F&DT evaluation in digital twin paradigm, a fatigue damage-cumulative model within peridynamic framework is proposed in this paper. Based on the concept of fatigue element block and damage accumulation law in form of Coffin-Manson relationship, the proposed model applies to both fatigue crack initiation and fatigue crack growth;fatigue crack growth rates under constant-amplitude and simple variable-amplitude block loading cases can be well predicted for three common structural materials without inputs of Paris law parameters. Additionally, the proposed model can also be easily extended to a probabilistic version;for verification, multiple-site-damage problems are simulated and the statistic nature of fatigue process in experiments can be well captured. In the end, main features of the proposed model are summarized, and distinctions from the other models are discussed. There may be a potential for the peridynamic damage-cumulative model proposed in this work to numerically predict fatigue problems in digital twin paradigm for future generations of aerospace vehicles.
基金supported by the National Natural Science Foundation of China(No.11272029)
文摘This paper presents an incremental cutting method for evaluating the longitudinal residual stresses in a butt welded thin plate via combining the traditional residual stress measurement methods and the advanced optical technique.The proposed approach,which can be called digital image correlation（DIC）-aided slitting technique,introduces a successive extension slot to a specimen and employs the DIC technique to measure the released displacement profiles of the cutting sections after each cutting increment.Then the displacement profiles are used to directly calculate the residual stress distributions up to the slot tip and hence,a stress distribution can be obtained after a cutting increment.Finally,all of the stress distributions are averaged to ultimately determine the original residual stress field.This method does not include any complex experimental operations or tedious derivation,and the resolution of stress variation is greatly improved by the continuous measurement of the released displacements.The presented method has been preliminarily verified by a specimen with residual stress introduced by a four-point bending test.The results show that residual stresses determined by the DIC-aided slitting technique agree well with those from finite element（FE） prediction.The residual stress in a friction stir welded aluminum specimen obtained by the presented technique is also consistent with the evaluations given by X-ray diffraction.Furthermore,the residual stresses obtained by the DIC-aided slitting technique demonstrate higher accuracy and stability than the evaluations derived by the DIC-aided contour method.
基金supported by the Chinese National Science Foundation(Grant No.52174345,52064032)the Yunnan Science and Technology Projects(Grant No.202002AB080001)Science and Technology Major Project of Yunnan Province(Grant No.202202AG050004).
文摘In order to uniformly disperse the ceramic reinforcements synthesized in-situ in the copper matrix composites,this study used Carbon Polymer Dot(CPD)as the carbon source and Cu–1.0%Ti alloy powder as the matrix for supplying Ti source to prepare in-situ synthesized TiC/Cu composites.The results show that TiC nano-precipitates,having the similar particle sizes with the CPD,form at the grains interior and grain boundaries,and maintain a uniform distribution state.Compared with the matrix,0.3 wt%CPD/Cu composite displays the best strengthplastic compatibility,the ultimate tensile strength achieves 385 MPa accompanied with a corresponding elongation of 21%,owing to the dislocation hindrance caused by nano-carbide and excellent interface bonding between nano TiC and the Cu matrix.The density function theory calculation supports our experimental results by showing a tighter and stronger interface contact.This work presents a new approach for studying in-situ carbide precipitates.
基金supported by the National Natural Science Foundation of China(Grant Nos.51771220,51771095,51422106)the Major Program of the Zhejiang Provincial Natural Science Foundation of China(Grant No.LD19E010001).
文摘Isotropic Sm-Co nanoparticle powders with high coercivity were prepared by high-energy ball milling followed by optimal annealing at different temperatures.The covercivity increased monotonically with increasing of the annealing temperature and a highest coercivity of 31.2 kOe was obtained.The sample with an optimal energy product of 17.0 MGOe still had a coercivity of 18.2 kOe.The evolution of phase,particle size,mechanism of coercivity and other related magnetic properties were analyzed.The excellent performance is attributed to nanoscale size grains below 15 nm and good exchange coupling between nanoparticles.
基金financially supported by the National Natural Science Foundation of China (Nos.52174345 and 52064032)the Science and Technology Major Project of Yunnan Province (No.202202AG050004)。
文摘The configuration and quality of reinforcements, as well as the robustness of interfacial bonding,holding a critical significance in determining the concurrence between electrical conductivity and mechanical strength in metal matrix composites. In this study, citric acid was employed as the precursor for synthesizing multiscale carbon nanomaterials(graphene quantum dots and graphene, abbreviated as GQDs and GN). The GQDs@GN/Cu composites were fabricated through a segmented ball milling process in conjunction with subsequent spark plasma sintering(SPS). The intragranular GQDs and intergranular GQDs@GN had synergistically reinforced Cu composites through Orowan strengthening, load transfer strengthening and refinement strengthening. Furthermore,the robust interface bonding between GQDs@GN and Cu effectively mitigated interfacial impedance stemming from electron-boundary scattering. The yield strength and ultimate tensile strength of the GQDs@GN/Cu composites were recorded as 270 and 314 MPa, respectively, representing an improvement of 92 and 28% over pure Cu, while maintaining electrical conductivity at a level comparable to that of pure Cu. This study advances the understanding of the possibility of realizing a synergistic compatibility between electrical conductivity and mechanical strength in Cu composites.
基金financially supported by Yunnan Fundamental Research Projects(No.202301BE070001-007)。
文摘Strengthening interface bonding between boron nitride nanosheets(BNNS)and copper matrix is an essential prerequisite for exploiting a new generation of copper matrix composites(CMCs)with high strength and wear resistance.Herein,BNNS/Cu composites were fabricated by the powder metallurgy route,matrix-alloying(adding 1.0 wt%Ti)strategy was adopted to improve the interfacial wettability and strengthen interface adhesion.A typical"sandwich"-like multiply interface structure involving TiN transition layers,BNNS and Cu matrix had been well constructed through the rational heat treatment(900℃ for 120 min).Additionally,nano-sized TiB whisker was in situ formed in the vicinity of the interface,it had linked the BNNS-Cu-TiN multiply interface,which played a role of"threading the needle"and significantly strengthened the multi-interfaces bonding.This specific interface structure was finely characterized,and the formation mechanism of solid-state interfacial reaction feature was proposed.The results demonstrated that the ultimate tensile strength(UTS)of BNNS/Cu-(Ti)-900℃ increased from 248 to 530 MPa(increased by 114%),and the coefficient of friction(COF)decreased from 0.51 to 0.28 than pure Cu.This work highlights the importance of interface configuration design,which contributes to the development of CMCs with prominent comprehensive properties.
基金supported by the National Natural Science Foundation of China(31960594)the Yunnan Fundamental Research Projects(202201AT070074,2019FB059)the Yunnan Technical Innovation Talent Training Project(202205AD160029).
文摘In this study,wild eggplant germplasm No.M239,which is highly susceptible to Verticillium wilt,was used as the experimental material.The physiological and biochemical indices(SOD,PAL,MDA and soluble protein)of M239 roots were measured at different times(0,12,24,36,48,60 and 72 h)post inoculation with Verticillium dahliae,and the key time points for the M239 response to Verticillium wilt infection were screened.Then,RNA-Seq technology was used to screen the differentially expressed genes(DEGs)in M239 roots at 0,12 and 48 h post-inoculation(hpi).The transcriptional results of M239 were also compared with those resistance genes from some reported wild relative Solanum species(S.sisymbriifolium and S.aculeatissimum).Then some DEGs were chosen for validation by qRT–PCR.The results showed that 12 and 48 hpi were the turning points in the changes in all physiological and biochemical indices.A total of 6,783 DEGs were identified by RNA-Seq,including 6,141 DEGs(3,046 upregulated and 3,095 downregulated)at the M_12 h vs.M_0 h,1,903 DEGs(792 upregulated and 1,111 downregulated)at M_48 h vs.M_12 h,and 1,261 DEGs that appeared simultaneously in both stages.KEGG enrichment analysis showed that there were 5 metabolic pathways enriched from DEGs,which were mostly related to primary metabolism,such as glycolysis,amino acid and ribosome biogenesis.Compared with the NCBI non-redundant protein(NR)database,one Ve2 homologous gene and 8 PR protein-related genes were screened.Transcription factor analysis showed that there were a large number of DEGs,such as MYB,AP2-EREBP,bHLH,NAC and Orphans in the two stages.Compared with the reported Verticillium wilt-resistant wild eggplant species,it was found that there were fewer genes and enriched metabolic pathways in the M239 response to Verticillium wilt infection,and it also lacked the response of some known key resistance genes.These results proved that the above resistance genes and metabolic pathways played a key role in the wild eggplant response to V.dahliae infection.
基金This paper is the phased results of the following projects,an undergraduate teaching reform research project of China University of Geosciences(Wuhan)General Teaching reform project(Project No.2021A36)the Key Project of Hubei Provincial Key Research Base of Humanities and Social Sciences(Project No.CJHIXM-02-202101)the Central University New Youth Research Foundation Project(Project No.G1323522065).
文摘Taking the wireless enamel(wireless enamel refers to make enamel works without filigree)production technique in jewelry practice course as the research object,combined with years of enamel teaching experience in the Gemmological Institute of China University of Geosciences(Wuhan),this study expounds the theoretical class,design preparation,creative idea and technique practice application from the course teaching objectives and the implementation,which also emphasizes the practical improvability of students’design practice ability and innovative thinking ability.During the period,it focuses on the core processes,such as wireless enamel glaze method,object correction,firing time,composite application and system integration,to help students solve the key and difficult problems in the wireless enamel firing process.
基金National Key R&D Program of China(2017YFE0131300,2019YFA0705000)National Natural Science Foundation of China(Nos.U1732268,61874128,61851406,11705262,11905282,12004116,12074400,and 11734009)+4 种基金Frontier Science Key Program of CAS(No.QYZDY-SSW-JSC032)Chinese-Austrian Cooperative R&D Project(No.GJHZ201950)Program of Shanghai Academic Research Leader(19XD1404600)Shanghai Sailing Program(No.19YF1456200,19YF1456400)K.C.Wong Education Foundation(GJTD-2019-11).
文摘The realization of high-quality(Q)resonators regardless of the underpinning material platforms has been a ceaseless pursuit,because the high-Q resonators provide an extreme environment for confining light to enable observations of many nonlinear optical phenomenon with high efficiencies.Here,photonic microresonators with a mean Q factor of 6.75×10^(6)were demonstrated on a 4H-silicon-carbide-on-insulator(4H-SiCOI)platform,as determined by a statistical analysis of tens of resonances.Using these devices,broadband frequency conversions,including second-,third-,and fourth-harmonic generations have been observed.Cascaded Raman lasing has also been demonstrated in our SiC microresonator for the first time,to the best of our knowledge.Meanwhile,by engineering the dispersion properties of the SiC microresonator,we have achieved broadband Kerr frequency combs covering from 1300 to 1700nm.Our demonstration represents a significant milestone in the development of SiC photonic integrated devices.
基金the National Natural Science Foundation of China(Grant No.81871615).
文摘The fast-developing synthetic biology(SB)has provided many genetic tools to reprogram and engineer cells for improved performance,novel functions,and diverse applications.Such cell engineering resources can play a critical role in the research and development of novel therapeutics.However,there are certain limitations and challenges in applying genetically engineered cells in clinical practice.This literature review updates the recent advances in biomedical applications,including diagnosis,treatment,and drug development,of SB-inspired cell engineering.It describes technologies and relevant examples in a clinical and experimental setup that may significantly impact the biomedicine field.At last,this review concludes the results with future directions to optimize the performances of synthetic gene circuits to regulate the therapeutic activities of cell-based tools in specific diseases.
基金the National Natural Science Foundation of China(NSFC)(Grant Nos.10874105 and 11704231).
文摘In view of wide applications of structured light fields and plasmonic vortices,we propose the concept of compound plasmonic vortex and design several structured plasmonic vortex generators.This kind of structured plasmonic vortex generators consists of multiple spiral nanoslits and they can generate two or more concentric plasmonic vortices.Different from Laguerre-Gaussian beam,the topological charge of the plasmonic vortex in different region is different.Theoretical analysis lays the basis for the design of radially structured plasmonic vortex generators and numerical simulations for several examples confirm the effectiveness of the design principle.The discussions about the interference of vortex fields definite the generation condition for the structured vortex.This work provides a design methodology for generating new vortices using spiral nanoslits and the advanced radially structured plasmonic vortices is helpful for broadening the applications of vortex fields.
基金Major Science and Technology Projects of Yunnan Province(grant No.202202AG050003).
文摘In this study,glucose and NH4F were utilized as sources of carbon and fluorine,respectively,for the synthesis of LiMn_(0.6)Fe_(0.4)PO_(4)(LMFP)nanoscales.These nanoscales were subsequently modified with varying levels of fluorine-doped carbon through co-precipitation and mechanical ball milling processes.The LMFP,incorporating carbon and varying levels of fluoride ions,exhibit higher specific discharge capacities at 0.2 Cand electrochemical characteristics compared to the original LMFP coated solely with carbon.The inclusion of fluorine-doped carbon in the composite material creates numerous pathways for expeditious electron transfer.Moreover,the partial formation of metal fluoride at the interface between the surface of LMFP and the layer of carbon coating doped with fluorine enhances the reduction in the charge-transfer resistance.The modified ferromanganese phosphate cathode material reveals an outstanding discharge capacity displaying a reversible discharge specific capacity value of 131.73 mA h g^(−1)at 10C and 154.6 mA h g^(−1)at 0.2C,due to its unique structure.
基金supported by the Ministry of Science and Technology of China(2022YFC2303700,2021YFA1301900)The National Natural Science Foundation of China(81871615,32222040,32070049)+1 种基金Tianjin Synthetic Biotechnology Innovation Capacity Improvement Action(TSBICIP-KJGG-008)supported in part by a Tibet Science Foundation grant(XZ202001ZY0036 N)to Yonghong Zhou。
文摘Tetracycline repressor(TetR)family regulators(TFRs)are the largest group of DNA-binding transcription factors and are widely distributed in bacteria and archaea.TFRs play vital roles in controlling the expression of various genes and regulating diverse physiological processes.Recently,a TFR protein Pseudomonas virulence regulator A(PvrA),was identified from Pseudomonas aeruginosa as the transcriptional activator of genes involved in fatty acid utilization and bacterial virulence.Here,we show that PvrA can simultaneously bind to multiple pseudo-palindromic sites and upregulate the expression levels of target genes.Cryo-electron microscopy(cryo-EM)analysis indicates the simultaneous DNA recognition mechanism of PvrA and suggests that the bound DNA fragments consist of a distorted B-DNA double helix.The crystal structure and functional analysis of PvrA reveal a hinge region that secures the correct domain motion for recognition of the promiscuous promoter.Additionally,our results showed that mutations disrupting the regulatory hinge region have differential effects on biofilm formation and pyocyanin biosynthesis,resulting in attenuated bacterial virulence.Collectively,these findings will improve the understanding of the relationship between the structure and function of the TetR family and provide new insights into the mechanism of regulation of P.aeruginosa virulence.
基金supported by the National Natural Science Foundation of China (Grant Nos. 92058207 & 42076037)the Fundamental Research Funds for the Central Universities (Grant No. 202042010)+1 种基金the Taishan Young Scholars (Grant No. tsqn202103030)the Shandong Province Natural Science Foundation (Grant No. ZR2021JQ12)。
文摘Marine dissolved organic matter (DOM) represents the largest carbon reservoir (~662 Pg carbon;Hansell, 2013). DOM in the ocean could be introduced from rivers, marine aerosols, and adjacent continental shelves, even produced, and transformed by physical processes (such as desorption and transfer), as well as microbial processes. A significant amount of DOM resists quick degradation and is classified as refractory DOM (RDOM) based on its reactivity and longevity (Hansell, 2013).
基金supported by the National Natural Science Foundation of China(Nos.52002015,22275010,22105016,and 52172241)the General Research Fund(Nos.CityU 11308120 and CityU 11308321)The authors thank the facility support of the 4B9A beamline of Beijing Synchrotron Radiation Facility(BSRF).
文摘Metallic phthalocyanines are promising electrocatalysts for CO_(2) reduction reaction(CO_(2)RR).However,their catalytic activity and stability(especially under high potential)are still unsatisfactory.Herein,we synthesized a covalent organic polymer(COP-CoPc)by introducing charge-switchable viologen ligands into cobalt phthalocyanine(CoPc).The COP-CoPc exhibits great activity for CO_(2)RR,including a high Faradaic efficiency over a wide potential window and the highest CO partial current density among all ligand-tuned phthalocyanine catalysts reported in the H-type cell.Particularly,COP-CoPc also shows great potential for practical applications,for example,a FECO of>95%is realized at a large current density of 150 mA/cm^(2) in a two-electrode membrane electrode assembly reactor.Ex situ and in situ X-ray absorption fine structure spectroscopy measurements and theory calculations reveal that when the charge-switchable viologen ligands switch to neutral-state ones,they can act as electron donors to enrich the electron density of Co centers in COP-CoPc and enhance the desorption of*CO,thus improving the CO selectivity.Moreover,the excellent reversible redox capability of viologen ligands and the increased Co–N bonding strength in the Co–N4 sites enable COP-CoPc to possess outstanding stability under elevated potentials and currents,enriching the knowledge of charge-switchable ligands tailored CO_(2)RR performance.
