Surface/underwater target classification is a key topic in marine information research.However,the complex underwater environment,coupled with the diversity of target types and their variable characteristics,presents ...Surface/underwater target classification is a key topic in marine information research.However,the complex underwater environment,coupled with the diversity of target types and their variable characteristics,presents significant challenges for classifier design.For shallow-water waveguides with a negative thermocline,a residual neural network(ResNet)model based on the sound field elevation structure is constructed.This model demonstrates robust classification performance even when facing low signal-to-noise ratios and environmental mismatches.Meanwhile,to address the reduced generalization ability caused by limited labeled acoustic data,an improved ResNet model based on unsupervised domain adaptation(“proposed UDA-ResNet”)is further constructed.This model incorporates data on simulated elevation structures of the sound field to augment the training process.Adversarial training is employed to extract domain-invariant features from simulated and trial data.These strategies help reduce the negative impact caused by domain differences.Experimental results demonstrate that the proposed method shows strong surface/underwater target classification ability under limited sample sizes,thus confirming its feasibility and effectiveness.展开更多
A feasible criterion was established to determine the lower size limit of raw coal(d_(pRm))for efficient beneficiation in the air-fluidized bed with magnetite particles.The feasibility of using small magnetite particl...A feasible criterion was established to determine the lower size limit of raw coal(d_(pRm))for efficient beneficiation in the air-fluidized bed with magnetite particles.The feasibility of using small magnetite particles to accommodate the fine raw coal was demonstrated from the experimental perspective.The minimum size for the magnetite particles to be fluidized smoothly was clarified as 47.1μm,which corresponded to the border between Geldart-B and-A groups.Since the gangue and coal components in the raw coal were crushed into the same size,d_(pRm)depended on the greater one between d_(pGm)(minimum size required for the gangue particles to sink towards the bottom)and d_(pCm)(minimum size required for the coal particles to float towards the top).dpcm was determined as 259μm by supposing that provided the gangue particles accumulated in the lower half bed,they could be potentially extracted from the bottom.On the other hand,it was observed that the coal particles could always accumulate in the upper half bed.Under such circumstances,dpcm was revealed as 9.8μm since finer coal particles would be blown out by air before the 47.1μm sized magnetite particles became fluidized.Eventually,dpRm was clarified as 259μm,agreeing with the common view that raw coal coarser than 6 mm could be effectively beneficiated in the air-fluidized bed with magnetite particles.Additionally,the difficulty in beneficiating the fine raw coal was revealed to arise more from the remixing of sorted gangue particles than that of separated coal particles.展开更多
A metallurgical model for austenite coarsening in the coarse-grained heat-affected zone(CGHAZ)containing titanium nitride(TiN)precipitation was studied.Unlike traditional methods estimating pinning capability based on...A metallurgical model for austenite coarsening in the coarse-grained heat-affected zone(CGHAZ)containing titanium nitride(TiN)precipitation was studied.Unlike traditional methods estimating pinning capability based on the precipitation size after welding,a proposed dissolution and coarsening model was applied to study the changes in TiN precipitation size and the associated pinning forces.The transmission electron microscope was used to analyze the size distribution of TiN particles before and after the welding thermal cycle.The size distribution showed a log-normal distribution before the thermal cycle.The prediction of post-thermal cycle size distributions with the proposed model was in agreement with the experimental results.Considering the short holding time at high temperature during welding,the thermodynamic stability conditions required for limiting grain size model cannot be achieved.A simple kinetic model for the prediction of austenite grain size in CGHAZ was established.Finally,the predicted austenite grain sizes agree better with experimental results than the conventional approach.展开更多
A low carbon hypoeutectoid steel(0.19 wt%C)with proeutectoid ferrite and pearlite dual-components was subjected to surface plastic deformation via pipe inner surface grinding(PISG)at room temperature.The deformation m...A low carbon hypoeutectoid steel(0.19 wt%C)with proeutectoid ferrite and pearlite dual-components was subjected to surface plastic deformation via pipe inner surface grinding(PISG)at room temperature.The deformation microstructures for each component were systematically characterized along depth,and the patterns of structural evolution toward nanometer regime as well as the governing parameters were addressed.Proeutectoid ferrite grains were refined down to 17 nm,and the pattern covering a length scale of 4–5 orders of magnitude from micron-to nanometer-scale follows:formation of cellular dislocation structure(CDS),elongated dislocation structure(EDS),ultrafine lamellar structure(UFL)and finally the nanolaminated structure(NL).The pearlite experiences the deformation and refinement,and finally the transforming the ultrafine pearlite(UFP)into nanolaminated pearlite(NLP)with the ferrite lamellae as thin as 20 nm.Refinement for both UFL(UFP)and NL(NLP)can be realized via forming novel extended boundaries within ferrite lamellae.A critical lattice curvature of~2.8°is required for forming such extended boundary,corresponding to a minimum strain gradient of 0.25μm^(-1)for a 100 nm-thick lamella.Refinement below size limit(expressed by lamellar thickness d_Tin nm)is correlated with the strain gradient(χ,inμm^(-1))by:d_T=12.5/x.Refinement contributions from strain gradient caused by PISG processing and material heterogeneity were discussed.展开更多
Additive manufacturing(AM),a key technology in the evolution of Industry 4.0,has revolutionized production processes by enabling the precise,layer-by-layer fabrication of complex and customized components,enhancing ef...Additive manufacturing(AM),a key technology in the evolution of Industry 4.0,has revolutionized production processes by enabling the precise,layer-by-layer fabrication of complex and customized components,enhancing efficiency and flexibility in smart manufacturing systems.However,one significant challenge hindering the acceptance of this technology is the limited print size,constrained by the machine’s small bed.To address this issue,a suitable polymer joining technique could be applied as a post-fabrication step.The present article examines findings on the Ultrasonic Welding(UW)of Material Extrusion(MEX)-3D printed parts made from commonly used thermoplastics,Acrylonitrile Butadiene Styrene(ABS)and Polylactic Acid(PLA).Key parameters in the process are identified and optimized through statistical methods,such as Design of Experiments(DOE),Taguchi,and Analysis of Variance(ANOVA).The findings showed that the material combination and the design of the energy directors had the greatest impact on the joint strength and elongation,leading to a joint efficiency increase of up to 174.52%.The research’s feasibility was additionally supported by applying the results to weld and fabricate a car’s rear wing and an agricultural drone,both of which demonstrated strong structural integrity.The proposed method is anticipated to increase acceptance of joining and welding techniques in the future,with UW showing significant potential for effectively joining 3D-printed parts and addressing the bed size limitations of 3D printers.展开更多
TiCx/Cu composites were fabricated by combustion synthesis and hot press technology. Using XRD, SEM, EDS, FESEM analysis methods, the effects of various carbon sources and different Cu contents on the microstructures ...TiCx/Cu composites were fabricated by combustion synthesis and hot press technology. Using XRD, SEM, EDS, FESEM analysis methods, the effects of various carbon sources and different Cu contents on the microstructures of TiCx/Cu composites and the size of TiCx particles were investigated. Results showed that TiCx reinforcing particles size increases with decreasing Cu content in Cu-Ti-C reaction system. With carbon nanotubes（carbon black） serving as carbon source, the generated TiCx particles size transits from nanometer to submicron when Cu content corresponding to the reaction system is reduced to 60 vol%（70 vol%）; while graphite serves as carbon source, there is no clear limiting concentration. C particles with smaller size, larger specific surface area and better distribution result in finer TiCx particles, which is more beneficial to generating nano-sized TiCx/Cu composites.展开更多
The South China Sea(SCS), which is the largest marginal sea in the western tropical Pacific, plays an important role in regional climate change. However, the research on the phytoplankton community structure(PCS) resp...The South China Sea(SCS), which is the largest marginal sea in the western tropical Pacific, plays an important role in regional climate change. However, the research on the phytoplankton community structure(PCS) response to the upwelling remains inadequate. In January 2014, the upwelling simulation experiment was performed in the western SCS. Results indicate that the nutrient-rich bottom water not only increased the total Chlorophyll a(Chl a) concentrations, but would potentially altered the PCS. Due to new nutrients added, microphytoplankton had more sensitivity response to nutrient uptake than other phytoplankton groups. The variation of nutrients induced by formation, weakening and disappearance of upwelling resulted in phytoplankton species succession from cyanophyta to bacillariophyta. It may be the leading factor of the changes in PCS and size-fractionated Chl a. The initial concentration of DIP less than 0.1 μmol L-1 could not sustain the phytoplankton growth. This indicates that phosphorus may be the limiting factor in the western SCS.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.62471024 and 62301183)the Open Research Fund of Hanjiang Laboratory(KF2024001).
文摘Surface/underwater target classification is a key topic in marine information research.However,the complex underwater environment,coupled with the diversity of target types and their variable characteristics,presents significant challenges for classifier design.For shallow-water waveguides with a negative thermocline,a residual neural network(ResNet)model based on the sound field elevation structure is constructed.This model demonstrates robust classification performance even when facing low signal-to-noise ratios and environmental mismatches.Meanwhile,to address the reduced generalization ability caused by limited labeled acoustic data,an improved ResNet model based on unsupervised domain adaptation(“proposed UDA-ResNet”)is further constructed.This model incorporates data on simulated elevation structures of the sound field to augment the training process.Adversarial training is employed to extract domain-invariant features from simulated and trial data.These strategies help reduce the negative impact caused by domain differences.Experimental results demonstrate that the proposed method shows strong surface/underwater target classification ability under limited sample sizes,thus confirming its feasibility and effectiveness.
基金supported by Shandong Provincial Natural Science Foundation(ZR2023MB038)Youth Innovation Team Program of Shandong Higher Education Institution(2022KJ156)。
文摘A feasible criterion was established to determine the lower size limit of raw coal(d_(pRm))for efficient beneficiation in the air-fluidized bed with magnetite particles.The feasibility of using small magnetite particles to accommodate the fine raw coal was demonstrated from the experimental perspective.The minimum size for the magnetite particles to be fluidized smoothly was clarified as 47.1μm,which corresponded to the border between Geldart-B and-A groups.Since the gangue and coal components in the raw coal were crushed into the same size,d_(pRm)depended on the greater one between d_(pGm)(minimum size required for the gangue particles to sink towards the bottom)and d_(pCm)(minimum size required for the coal particles to float towards the top).dpcm was determined as 259μm by supposing that provided the gangue particles accumulated in the lower half bed,they could be potentially extracted from the bottom.On the other hand,it was observed that the coal particles could always accumulate in the upper half bed.Under such circumstances,dpcm was revealed as 9.8μm since finer coal particles would be blown out by air before the 47.1μm sized magnetite particles became fluidized.Eventually,dpRm was clarified as 259μm,agreeing with the common view that raw coal coarser than 6 mm could be effectively beneficiated in the air-fluidized bed with magnetite particles.Additionally,the difficulty in beneficiating the fine raw coal was revealed to arise more from the remixing of sorted gangue particles than that of separated coal particles.
基金supported by the National Natural Science Foundation of China(U21A20116).
文摘A metallurgical model for austenite coarsening in the coarse-grained heat-affected zone(CGHAZ)containing titanium nitride(TiN)precipitation was studied.Unlike traditional methods estimating pinning capability based on the precipitation size after welding,a proposed dissolution and coarsening model was applied to study the changes in TiN precipitation size and the associated pinning forces.The transmission electron microscope was used to analyze the size distribution of TiN particles before and after the welding thermal cycle.The size distribution showed a log-normal distribution before the thermal cycle.The prediction of post-thermal cycle size distributions with the proposed model was in agreement with the experimental results.Considering the short holding time at high temperature during welding,the thermodynamic stability conditions required for limiting grain size model cannot be achieved.A simple kinetic model for the prediction of austenite grain size in CGHAZ was established.Finally,the predicted austenite grain sizes agree better with experimental results than the conventional approach.
基金the Hundred Outstanding Creative Talents Projects in Hebei University,Chinathe Project Program of Heavy Machinery Collaborative Innovation CenterChina and the National Natural Science Foundation of China(No.51171182)。
文摘A low carbon hypoeutectoid steel(0.19 wt%C)with proeutectoid ferrite and pearlite dual-components was subjected to surface plastic deformation via pipe inner surface grinding(PISG)at room temperature.The deformation microstructures for each component were systematically characterized along depth,and the patterns of structural evolution toward nanometer regime as well as the governing parameters were addressed.Proeutectoid ferrite grains were refined down to 17 nm,and the pattern covering a length scale of 4–5 orders of magnitude from micron-to nanometer-scale follows:formation of cellular dislocation structure(CDS),elongated dislocation structure(EDS),ultrafine lamellar structure(UFL)and finally the nanolaminated structure(NL).The pearlite experiences the deformation and refinement,and finally the transforming the ultrafine pearlite(UFP)into nanolaminated pearlite(NLP)with the ferrite lamellae as thin as 20 nm.Refinement for both UFL(UFP)and NL(NLP)can be realized via forming novel extended boundaries within ferrite lamellae.A critical lattice curvature of~2.8°is required for forming such extended boundary,corresponding to a minimum strain gradient of 0.25μm^(-1)for a 100 nm-thick lamella.Refinement below size limit(expressed by lamellar thickness d_Tin nm)is correlated with the strain gradient(χ,inμm^(-1))by:d_T=12.5/x.Refinement contributions from strain gradient caused by PISG processing and material heterogeneity were discussed.
文摘Additive manufacturing(AM),a key technology in the evolution of Industry 4.0,has revolutionized production processes by enabling the precise,layer-by-layer fabrication of complex and customized components,enhancing efficiency and flexibility in smart manufacturing systems.However,one significant challenge hindering the acceptance of this technology is the limited print size,constrained by the machine’s small bed.To address this issue,a suitable polymer joining technique could be applied as a post-fabrication step.The present article examines findings on the Ultrasonic Welding(UW)of Material Extrusion(MEX)-3D printed parts made from commonly used thermoplastics,Acrylonitrile Butadiene Styrene(ABS)and Polylactic Acid(PLA).Key parameters in the process are identified and optimized through statistical methods,such as Design of Experiments(DOE),Taguchi,and Analysis of Variance(ANOVA).The findings showed that the material combination and the design of the energy directors had the greatest impact on the joint strength and elongation,leading to a joint efficiency increase of up to 174.52%.The research’s feasibility was additionally supported by applying the results to weld and fabricate a car’s rear wing and an agricultural drone,both of which demonstrated strong structural integrity.The proposed method is anticipated to increase acceptance of joining and welding techniques in the future,with UW showing significant potential for effectively joining 3D-printed parts and addressing the bed size limitations of 3D printers.
文摘TiCx/Cu composites were fabricated by combustion synthesis and hot press technology. Using XRD, SEM, EDS, FESEM analysis methods, the effects of various carbon sources and different Cu contents on the microstructures of TiCx/Cu composites and the size of TiCx particles were investigated. Results showed that TiCx reinforcing particles size increases with decreasing Cu content in Cu-Ti-C reaction system. With carbon nanotubes（carbon black） serving as carbon source, the generated TiCx particles size transits from nanometer to submicron when Cu content corresponding to the reaction system is reduced to 60 vol%（70 vol%）; while graphite serves as carbon source, there is no clear limiting concentration. C particles with smaller size, larger specific surface area and better distribution result in finer TiCx particles, which is more beneficial to generating nano-sized TiCx/Cu composites.
基金upport of the National Programme on Global Change and Air-Sea Interaction (GASI-03-01-02-01)
文摘The South China Sea(SCS), which is the largest marginal sea in the western tropical Pacific, plays an important role in regional climate change. However, the research on the phytoplankton community structure(PCS) response to the upwelling remains inadequate. In January 2014, the upwelling simulation experiment was performed in the western SCS. Results indicate that the nutrient-rich bottom water not only increased the total Chlorophyll a(Chl a) concentrations, but would potentially altered the PCS. Due to new nutrients added, microphytoplankton had more sensitivity response to nutrient uptake than other phytoplankton groups. The variation of nutrients induced by formation, weakening and disappearance of upwelling resulted in phytoplankton species succession from cyanophyta to bacillariophyta. It may be the leading factor of the changes in PCS and size-fractionated Chl a. The initial concentration of DIP less than 0.1 μmol L-1 could not sustain the phytoplankton growth. This indicates that phosphorus may be the limiting factor in the western SCS.
