Surface classification, 3D parting line, parting surface generation and demoldability analysis which is helpful to select optimal parting direction and optimal parting line are involved in auto-matic cavity design bas...Surface classification, 3D parting line, parting surface generation and demoldability analysis which is helpful to select optimal parting direction and optimal parting line are involved in auto-matic cavity design based on the my-testing model. A new ray-testing approach is presented to classify the part surfaces to core/cavity surfaces and undercut surfaces by automatic identifying the visibility of surfaces. A simple, direct and efficient algorithm to identify surface visibility is developed. The algorithm is robust and adapted to rather complicated geometry, so it is valuable in computer-aided mold design systems. To validate the efficiency of the approach, an experimental program is implemented. Case studies show that the approach is practical and valuable in automatic parting line and parting surface generation.展开更多
The analyses of different sulfur forms, the trace elements in pyrites using electron microprobe and the trace elements in coal using INAA (instrumental neutron activation analysis) of the Late Paleozoic coals from the...The analyses of different sulfur forms, the trace elements in pyrites using electron microprobe and the trace elements in coal using INAA (instrumental neutron activation analysis) of the Late Paleozoic coals from the Taozao coalfield in Shandong Province, China, conclude that most sulfur (>75 %) in high-sulfur coal of Taiyuan Formation occurred as pyrite, in which many hazardous elements co-existed and their concentrations varied with their geological origin. The concentrations of hazardous elements in high-sulfur coals from Taiyuan Formation, composing mainly of Cu, As, U, Pb, Mo and Co, are much higher than those in the low-sulfur coals from Shanxi Formation and Shihezi Formation, because the influence of seawater during and after coal accumulation in Taiyuan Formation is stronger than those in Shanxi and Shihezi formations. Moreover, the element As is related to Fe, and both elements exist mainly in the form of pyrite. The element U is richer in the coal influenced by seawater. In addition, the coal affected by the magmatism contains more U, too. When high-sulfur coals are processed with heavy media washing to remove sulfur and minerals, the majority of hazardous elements will also be removed from the coals.展开更多
On the basis of the comprehensive analysis about the automatic generation of the injection mold parting surface, the parting surface design method which introduces knowledge and case-based reasoning （CBR） into the c...On the basis of the comprehensive analysis about the automatic generation of the injection mold parting surface, the parting surface design method which introduces knowledge and case-based reasoning （CBR） into the computer-aided design is described by combining with the actual characteristic in injection mold design, and the design process of case-based reasoning method is also given. A case library including the information of parting surface is built with the index of main shape features, The automatic design of the mold parting surface is realized combined with the forward-reasoning method and the similarity solution procedure. The rule knowledge library is also founded including the knowledge, principles and experiences for parting surface design. An example is used to show the validity of the method, and the quality and the efficiency of the mold design are improved.展开更多
It is critical to identify core/cavity and undercut surfaces of molds in parting line generation. A new Ray-Testing approach is presented to detect these surfaces by identifying the visibility of surfaces. A simple, d...It is critical to identify core/cavity and undercut surfaces of molds in parting line generation. A new Ray-Testing approach is presented to detect these surfaces by identifying the visibility of surfaces. A simple, direct and efficient algorithm to identify surface visibility is developed. Case studies show that the approach is practical and valuable in automated parting line generation.展开更多
A CAD approach which can optimize and automate the parting direction determination is presented. The approach is based on the geometrical and topological information of the solid modelling of the plastic moulded part ...A CAD approach which can optimize and automate the parting direction determination is presented. The approach is based on the geometrical and topological information of the solid modelling of the plastic moulded part in order to select a pair of optimal parting directions of a two plate mould which minimizes the number of side cores. The shell of a part is divided into inter influential regions and non influential faces in the mould design point of view. Through analyzing and computing the accessibility direction cones of the inter influential regions, the optimal parting directions can be determined automatically.展开更多
Large size titanium alloy parts are widely used in aerospace.However,they are difficult to manufacture using mechanical cutting technology because of severe tool wear.Electrochemical jet machining is a promising techn...Large size titanium alloy parts are widely used in aerospace.However,they are difficult to manufacture using mechanical cutting technology because of severe tool wear.Electrochemical jet machining is a promising technology to achieve high efficiency,because it has high machining flexibility and no machining tool wear.However,reports on the macro electrochemical jet machining of large size titanium alloy parts are very scarce,because it is difficult to achieve effective constraint of the flow field in macro electrochemical jet machining.In addition,titanium alloy is very sensitive to fluctuation of the flow field,and a turbulent flow field would lead to serious stray corrosion.This paper reports a series of investigations of the electrochemical jet machining of titanium alloy parts.Based on the flow analysis and experiments,the machining flow field was effectively constrained.TB6 titanium alloy part with a perimeter of one meter was machined.The machined surface was smooth with no obvious machining defects.The machining process was particularly stable with no obvious spark discharge.The research provides a reference for the application of electrochemical jet machining technology to achieve large allowance material removal in the machining of large titanium alloy parts.展开更多
In the face of data scarcity in the optimization of maintenance strategies for civil aircraft,traditional failure data-driven methods are encountering challenges owing to the increasing reliability of aircraft design....In the face of data scarcity in the optimization of maintenance strategies for civil aircraft,traditional failure data-driven methods are encountering challenges owing to the increasing reliability of aircraft design.This study addresses this issue by presenting a novel combined data fusion algorithm,which serves to enhance the accuracy and reliability of failure rate analysis for a specific aircraft model by integrating historical failure data from similar models as supplementary information.Through a comprehensive analysis of two different maintenance projects,this study illustrates the application process of the algorithm.Building upon the analysis results,this paper introduces the innovative equal integral value method as a replacement for the conventional equal interval method in the context of maintenance schedule optimization.The Monte Carlo simulation example validates that the equivalent essential value method surpasses the traditional method by over 20%in terms of inspection efficiency ratio.This discovery indicates that the equal critical value method not only upholds maintenance efficiency but also substantially decreases workload and maintenance costs.The findings of this study open up novel perspectives for airlines grappling with data scarcity,offer fresh strategies for the optimization of aviation maintenance practices,and chart a new course toward achieving more efficient and cost-effective maintenance schedule optimization through refined data analysis.展开更多
It’s a pleasure to be here and speak about the industrial copilot and generative AI and the changing applications.As you all know,generative AI has arrived since a few years ago,we have generative AI not only in the ...It’s a pleasure to be here and speak about the industrial copilot and generative AI and the changing applications.As you all know,generative AI has arrived since a few years ago,we have generative AI not only in the consumer world,but also in the industrial world.Siemens is very active in the industrial space.We need to make AI real,because at the end in industry manufacturing,you are producing parts in the real world.So we need to make sure that AI and its applications can interact and comply with the real world.展开更多
It has long been noticed that focus is able to influence the truth-conditions of coun-terfactual conditionals.Namely,stressing different parts of a counterfactual leads to distinct interpretations.However,existing the...It has long been noticed that focus is able to influence the truth-conditions of coun-terfactual conditionals.Namely,stressing different parts of a counterfactual leads to distinct interpretations.However,existing theories,such as those by von Finte1 and Rooth,fail to ad-equately account for this phenomenon.In this paper,I exposit the drawbacks of these theories and then propose a novel account,ie.the Good Question-Answer(GQA)view.The GQA account posits that focus triggers question-answer pairs,and pragmatic pressures conceming the adequacy of such question answer pairs in contexts are able to affect the truth-conditions of counterfactuals.I also argue for the GQA account by appeal to its theoretical virtues.展开更多
To meet the increased demand for light-weight and high-performance special-shaped load bearing parts in automotive industry,the short carbon fiber reinforced magnesium matrix composite(C_(sf)/Mg)part with complex conf...To meet the increased demand for light-weight and high-performance special-shaped load bearing parts in automotive industry,the short carbon fiber reinforced magnesium matrix composite(C_(sf)/Mg)part with complex configuration features and abrupt cross-sectional transitions was fabricated by liquid-solid extrusion following vacuum pressure infiltration process(LSEVI).Near-net forming schemes of both the special-shaped fiber preform and composite part were proposed.The effect of process parameters on the forming quality of the composite part was discussed.Meanwhile,the microstructures and compressive properties in different regions of the part were analyzed.The results show that the forward forming scheme provides the special-shaped fiber preform with no surface defects.For the C_(sf)/AZ91D part,its internal microstructures show that the infiltration of liquid magnesium is sufficient and uniform.The compressive strength of the composite part can reach up to 487 MPa,corresponding to~40%increase compared to 335 MPa of the AZ91D alloy.The average compressive strain of composites is less than 10%,which is about 50%of that of the AZ91D alloy.When the fiber orientation is parallel to the shear direction on the shear plane,the load-bearing capacity of the fiber is much higher than that of the fiber perpendicular to the shear direction.This work not only provides a convenient approach to fabricate special-shaped preform with high fiber volume fraction,but also gives a demonstration for the near-net forming of C_(sf)/Mg parts with excellent material isotropy and compressive properties.展开更多
The somatotopic representation of specific body parts is a well-established spatial organizational principle in the primary somatosensory and motor cortices.
We investigate the quantum dynamics of the 1D spinless Fermi-Hubbard model with a linear-tilted potential.Surprisingly in a strong resonance regime,we show that the model can be described by the kinetically constraine...We investigate the quantum dynamics of the 1D spinless Fermi-Hubbard model with a linear-tilted potential.Surprisingly in a strong resonance regime,we show that the model can be described by the kinetically constrained effective Hamiltonian,and it can be spontaneously divided into two commuting parts dubbed Hamiltonian dimerization,which are composed of two distinct sets of constrained nearest-neighbor hopping terms:one set acting exclusively on odd bonds and the other on even bonds.Specifically it is shown that each part can be independently mapped onto the well-known PXP model;therefore the dimerized Hamiltonian is equivalent to a two-fold PXP model.As a consequence,we numerically demonstrate this system can host the so-called quantum many-body scars,which present dynamical revivals and ergodicity-breaking behaviors.However,in sharp contrast with traditional quantum many-body scars,here the scarring states in our model driven by different parts of the Hamiltonian will revive in different periods,and those of double parts can display a biperiodic revival pattern,both originating from the Hamiltonian dimerization.Besides,the condition of off-resonance is also discussed,and we show the crossover from quantum many-body scar to ergodicity breaking is diagnosed via level statistics.Our model provides a platform for understanding the interplay of Hilbert space fragmentation and the constrained quantum systems.展开更多
On July 17,2024,Chinese electric vehicle manufacturer GAC International opened a smart factory in Rayong Province,Thailand.The next day,then Prime Minister of Thailand Saita Thawaixin met with a delegation led by Zeng...On July 17,2024,Chinese electric vehicle manufacturer GAC International opened a smart factory in Rayong Province,Thailand.The next day,then Prime Minister of Thailand Saita Thawaixin met with a delegation led by Zeng Qinghong,chairman of GAC Group.He encouraged GAC to purchase various spare parts in Thailand to enhance Thailand’s position in the global electric vehicle industry supply chain.“Thailand has a favorable business environment,”Zeng responded.“As the location of GAC’s first wholly-owned overseas facility,it was our premier choice.”展开更多
Ensuring the long-term and stable operation of mechanical equipment has been a research emphasis with the development of aerospace and polar exploration,which necessitates the prepared materials with high mechanical s...Ensuring the long-term and stable operation of mechanical equipment has been a research emphasis with the development of aerospace and polar exploration,which necessitates the prepared materials with high mechanical strength as well as excellent wear resistance[1].The traditional lubricant is widely acknowledged to be susceptible to evaporation or decomposition under extreme conditions,necessitating the deposition of a protective thin film on critical mechanical parts’surfaces to enhance their mechanical and tribological properties[2,3].展开更多
Additive manufacturing provides achievability for the fabrication of bimetallic and multi-material structures;however,the material compatibility and bondability directly affect the parts’formability and final quality...Additive manufacturing provides achievability for the fabrication of bimetallic and multi-material structures;however,the material compatibility and bondability directly affect the parts’formability and final quality.It is essential to understand the underlying printability of different material combinations based on an adapted process.Here,the printability disparities of two common and attractive material combinations(nickel-and iron-based alloys)are evaluated at the macro and micro levels via laser directed energy deposition(DED).The deposition processes were captured using in situ high-speed imaging,and the dissimilarities in melt pool features and track morphology were quantitatively investigated within specific process windows.Moreover,the microstructure diversity of the tracks and blocks processed with varied material pairs was comparatively elaborated and,complemented with the informative multi-physics modeling,the presented non-uniformity in mechanical properties(microhardness)among the heterogeneous material pairs was rationalized.The differences in melt flow induced by the unlike thermophysical properties of the material pairs and the resulting element intermixing and localized re-alloying during solidification dominate the presented dissimilarity in printability among the material combinations.This work provides an in-depth understanding of the phenomenological differences in the deposition of dissimilar materials and aims to guide more reliable DED forming of bimetallic parts.展开更多
An increasing number of researchers have researched fixture layout optimization for thin-walled part assembly during the past decades.However,few papers systematically review these researches.By analyzing existing lit...An increasing number of researchers have researched fixture layout optimization for thin-walled part assembly during the past decades.However,few papers systematically review these researches.By analyzing existing literature,this paper summarizes the process of fixture layout optimization and the methods applied.The process of optimization is made up of optimization objective setting,assembly variation/deformation modeling,and fixture layout optimization.This paper makes a review of the fixture layout for thin-walled parts according to these three steps.First,two different kinds of optimization objectives are introduced.Researchers usually consider in-plane variations or out-of-plane deformations when designing objectives.Then,modeling methods for assembly variation and deformation are divided into two categories:Mechanism-based and data-based methods.Several common methods are discussed respectively.After that,optimization algorithms are reviewed systematically.There are two kinds of optimization algorithms:Traditional nonlinear programming and heuristic algorithms.Finally,discussions on the current situation are provided.The research direction of fixture layout optimization in the future is discussed from three aspects:Objective setting,improving modeling accuracy and optimization algorithms.Also,a new research point for fixture layout optimization is discussed.This paper systematically reviews the research on fixture layout optimization for thin-walled parts,and provides a reference for future research in this field.展开更多
Stereolithography(SLA)combined with a two-step post-processing method“oxidation−reduction”was developed to fabricate pure copper with high complexity.The copper slurries for SLA were prepared,and particularly the in...Stereolithography(SLA)combined with a two-step post-processing method“oxidation−reduction”was developed to fabricate pure copper with high complexity.The copper slurries for SLA were prepared,and particularly the influence of volume fraction of copper on the properties of copper slurries was investigated.In the two-step post-treatment process,organics were removed by oxidation and copper powder was oxidized simultaneously,and then the oxidized copper was reduced into highly reactive copper particles,improving the sintering activity of the copper green body and enhancing the relative density of the sintered part.The results show that curing depth of the copper slurries decreased with the increase of volume fraction of copper.The viscosity of the pure copper slurry rises exponentially as the volume fraction of copper exceeded 50%.The highest volume fraction of pure copper slurry for SLA is 55%.The specimens exhibited an increase in hardness and electrical conductivity with the increase of volume fraction of copper.Specifically,the maximum values of hardness and conductivity of samples with 55 vol.%copper were HV 52.7 and 57.1%(IACS),respectively.展开更多
Prompt radiation emitted during accelerator operation poses a significant health risk,necessitating a thorough search and securing of hazardous areas prior to initiation.Currently,manual sweep methods are employed.How...Prompt radiation emitted during accelerator operation poses a significant health risk,necessitating a thorough search and securing of hazardous areas prior to initiation.Currently,manual sweep methods are employed.However,the limitations of manual sweeps have become increasingly evident with the implementation of large-scale accelerators.By leveraging advancements in machine vision technology,the automatic identification of stranded personnel in controlled areas through camera imagery presents a viable solution for efficient search and security.Given the criticality of personal safety for stranded individuals,search and security processes must be sufficiently reliable.To ensure comprehensive coverage,180°camera groups were strategically positioned on both sides of the accelerator tunnel to eliminate blind spots within the monitoring range.The YOLOV8 network model was modified to enable the detection of small targets,such as hands and feet,as well as larger targets formed by individuals near the cameras.Furthermore,the system incorporates a pedestrian recognition model that detects human body parts,and an information fusion strategy is used to integrate the detected head,hands,and feet with the identified pedestrians as a cohesive unit.This strategy enhanced the capability of the model to identify pedestrians obstructed by equipment,resulting in a notable improvement in the recall rate.Specifically,recall rates of 0.915 and 0.82were obtained for Datasets 1 and 2,respectively.Although there was a slight decrease in accuracy,it aligned with the intended purpose of the search-and-secure software design.Experimental tests conducted within an accelerator tunnel demonstrated the effectiveness of this approach in achieving reliable recognition outcomes.展开更多
This study proposes an image-based three-dimensional(3D)vector reconstruction of industrial parts that can gener-ate non-uniform rational B-splines(NURBS)surfaces with high fidelity and flexibility.The contributions o...This study proposes an image-based three-dimensional(3D)vector reconstruction of industrial parts that can gener-ate non-uniform rational B-splines(NURBS)surfaces with high fidelity and flexibility.The contributions of this study include three parts:first,a dataset of two-dimensional images is constructed for typical industrial parts,including hex-agonal head bolts,cylindrical gears,shoulder rings,hexagonal nuts,and cylindrical roller bearings;second,a deep learning algorithm is developed for parameter extraction of 3D industrial parts,which can determine the final 3D parameters and pose information of the reconstructed model using two new nets,CAD-ClassNet and CAD-ReconNet;and finally,a 3D vector shape reconstruction of mechanical parts is presented to generate NURBS from the obtained shape parameters.The final reconstructed models show that the proposed approach is highly accurate,efficient,and practical.展开更多
文摘Surface classification, 3D parting line, parting surface generation and demoldability analysis which is helpful to select optimal parting direction and optimal parting line are involved in auto-matic cavity design based on the my-testing model. A new ray-testing approach is presented to classify the part surfaces to core/cavity surfaces and undercut surfaces by automatic identifying the visibility of surfaces. A simple, direct and efficient algorithm to identify surface visibility is developed. The algorithm is robust and adapted to rather complicated geometry, so it is valuable in computer-aided mold design systems. To validate the efficiency of the approach, an experimental program is implemented. Case studies show that the approach is practical and valuable in automatic parting line and parting surface generation.
文摘The analyses of different sulfur forms, the trace elements in pyrites using electron microprobe and the trace elements in coal using INAA (instrumental neutron activation analysis) of the Late Paleozoic coals from the Taozao coalfield in Shandong Province, China, conclude that most sulfur (>75 %) in high-sulfur coal of Taiyuan Formation occurred as pyrite, in which many hazardous elements co-existed and their concentrations varied with their geological origin. The concentrations of hazardous elements in high-sulfur coals from Taiyuan Formation, composing mainly of Cu, As, U, Pb, Mo and Co, are much higher than those in the low-sulfur coals from Shanxi Formation and Shihezi Formation, because the influence of seawater during and after coal accumulation in Taiyuan Formation is stronger than those in Shanxi and Shihezi formations. Moreover, the element As is related to Fe, and both elements exist mainly in the form of pyrite. The element U is richer in the coal influenced by seawater. In addition, the coal affected by the magmatism contains more U, too. When high-sulfur coals are processed with heavy media washing to remove sulfur and minerals, the majority of hazardous elements will also be removed from the coals.
文摘On the basis of the comprehensive analysis about the automatic generation of the injection mold parting surface, the parting surface design method which introduces knowledge and case-based reasoning （CBR） into the computer-aided design is described by combining with the actual characteristic in injection mold design, and the design process of case-based reasoning method is also given. A case library including the information of parting surface is built with the index of main shape features, The automatic design of the mold parting surface is realized combined with the forward-reasoning method and the similarity solution procedure. The rule knowledge library is also founded including the knowledge, principles and experiences for parting surface design. An example is used to show the validity of the method, and the quality and the efficiency of the mold design are improved.
文摘It is critical to identify core/cavity and undercut surfaces of molds in parting line generation. A new Ray-Testing approach is presented to detect these surfaces by identifying the visibility of surfaces. A simple, direct and efficient algorithm to identify surface visibility is developed. Case studies show that the approach is practical and valuable in automated parting line generation.
文摘A CAD approach which can optimize and automate the parting direction determination is presented. The approach is based on the geometrical and topological information of the solid modelling of the plastic moulded part in order to select a pair of optimal parting directions of a two plate mould which minimizes the number of side cores. The shell of a part is divided into inter influential regions and non influential faces in the mould design point of view. Through analyzing and computing the accessibility direction cones of the inter influential regions, the optimal parting directions can be determined automatically.
基金the National Natural Science Foundation of China(No.52205468)China Postdoctoral Science Foundation(No.2022M710061 and No.2023T160277)Natural Science Foundation of Jiangsu Province(No.BK20210755)。
文摘Large size titanium alloy parts are widely used in aerospace.However,they are difficult to manufacture using mechanical cutting technology because of severe tool wear.Electrochemical jet machining is a promising technology to achieve high efficiency,because it has high machining flexibility and no machining tool wear.However,reports on the macro electrochemical jet machining of large size titanium alloy parts are very scarce,because it is difficult to achieve effective constraint of the flow field in macro electrochemical jet machining.In addition,titanium alloy is very sensitive to fluctuation of the flow field,and a turbulent flow field would lead to serious stray corrosion.This paper reports a series of investigations of the electrochemical jet machining of titanium alloy parts.Based on the flow analysis and experiments,the machining flow field was effectively constrained.TB6 titanium alloy part with a perimeter of one meter was machined.The machined surface was smooth with no obvious machining defects.The machining process was particularly stable with no obvious spark discharge.The research provides a reference for the application of electrochemical jet machining technology to achieve large allowance material removal in the machining of large titanium alloy parts.
文摘In the face of data scarcity in the optimization of maintenance strategies for civil aircraft,traditional failure data-driven methods are encountering challenges owing to the increasing reliability of aircraft design.This study addresses this issue by presenting a novel combined data fusion algorithm,which serves to enhance the accuracy and reliability of failure rate analysis for a specific aircraft model by integrating historical failure data from similar models as supplementary information.Through a comprehensive analysis of two different maintenance projects,this study illustrates the application process of the algorithm.Building upon the analysis results,this paper introduces the innovative equal integral value method as a replacement for the conventional equal interval method in the context of maintenance schedule optimization.The Monte Carlo simulation example validates that the equivalent essential value method surpasses the traditional method by over 20%in terms of inspection efficiency ratio.This discovery indicates that the equal critical value method not only upholds maintenance efficiency but also substantially decreases workload and maintenance costs.The findings of this study open up novel perspectives for airlines grappling with data scarcity,offer fresh strategies for the optimization of aviation maintenance practices,and chart a new course toward achieving more efficient and cost-effective maintenance schedule optimization through refined data analysis.
文摘It’s a pleasure to be here and speak about the industrial copilot and generative AI and the changing applications.As you all know,generative AI has arrived since a few years ago,we have generative AI not only in the consumer world,but also in the industrial world.Siemens is very active in the industrial space.We need to make AI real,because at the end in industry manufacturing,you are producing parts in the real world.So we need to make sure that AI and its applications can interact and comply with the real world.
基金supported by the Major Program of National Social Science Foundation of China(No.23&ZD240)。
文摘It has long been noticed that focus is able to influence the truth-conditions of coun-terfactual conditionals.Namely,stressing different parts of a counterfactual leads to distinct interpretations.However,existing theories,such as those by von Finte1 and Rooth,fail to ad-equately account for this phenomenon.In this paper,I exposit the drawbacks of these theories and then propose a novel account,ie.the Good Question-Answer(GQA)view.The GQA account posits that focus triggers question-answer pairs,and pragmatic pressures conceming the adequacy of such question answer pairs in contexts are able to affect the truth-conditions of counterfactuals.I also argue for the GQA account by appeal to its theoretical virtues.
基金support from the National Natural Science Foundation of China (No.52231004,52175365,51972271)Dr.Jiawei Fu appreciates the support from The Young Talents Plan in Shaanxi Province of China (No.00121)。
文摘To meet the increased demand for light-weight and high-performance special-shaped load bearing parts in automotive industry,the short carbon fiber reinforced magnesium matrix composite(C_(sf)/Mg)part with complex configuration features and abrupt cross-sectional transitions was fabricated by liquid-solid extrusion following vacuum pressure infiltration process(LSEVI).Near-net forming schemes of both the special-shaped fiber preform and composite part were proposed.The effect of process parameters on the forming quality of the composite part was discussed.Meanwhile,the microstructures and compressive properties in different regions of the part were analyzed.The results show that the forward forming scheme provides the special-shaped fiber preform with no surface defects.For the C_(sf)/AZ91D part,its internal microstructures show that the infiltration of liquid magnesium is sufficient and uniform.The compressive strength of the composite part can reach up to 487 MPa,corresponding to~40%increase compared to 335 MPa of the AZ91D alloy.The average compressive strain of composites is less than 10%,which is about 50%of that of the AZ91D alloy.When the fiber orientation is parallel to the shear direction on the shear plane,the load-bearing capacity of the fiber is much higher than that of the fiber perpendicular to the shear direction.This work not only provides a convenient approach to fabricate special-shaped preform with high fiber volume fraction,but also gives a demonstration for the near-net forming of C_(sf)/Mg parts with excellent material isotropy and compressive properties.
文摘The somatotopic representation of specific body parts is a well-established spatial organizational principle in the primary somatosensory and motor cortices.
基金supported by the National Key R&D Program of China(Grant No.2023YFA1406002)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0301200)。
文摘We investigate the quantum dynamics of the 1D spinless Fermi-Hubbard model with a linear-tilted potential.Surprisingly in a strong resonance regime,we show that the model can be described by the kinetically constrained effective Hamiltonian,and it can be spontaneously divided into two commuting parts dubbed Hamiltonian dimerization,which are composed of two distinct sets of constrained nearest-neighbor hopping terms:one set acting exclusively on odd bonds and the other on even bonds.Specifically it is shown that each part can be independently mapped onto the well-known PXP model;therefore the dimerized Hamiltonian is equivalent to a two-fold PXP model.As a consequence,we numerically demonstrate this system can host the so-called quantum many-body scars,which present dynamical revivals and ergodicity-breaking behaviors.However,in sharp contrast with traditional quantum many-body scars,here the scarring states in our model driven by different parts of the Hamiltonian will revive in different periods,and those of double parts can display a biperiodic revival pattern,both originating from the Hamiltonian dimerization.Besides,the condition of off-resonance is also discussed,and we show the crossover from quantum many-body scar to ergodicity breaking is diagnosed via level statistics.Our model provides a platform for understanding the interplay of Hilbert space fragmentation and the constrained quantum systems.
文摘On July 17,2024,Chinese electric vehicle manufacturer GAC International opened a smart factory in Rayong Province,Thailand.The next day,then Prime Minister of Thailand Saita Thawaixin met with a delegation led by Zeng Qinghong,chairman of GAC Group.He encouraged GAC to purchase various spare parts in Thailand to enhance Thailand’s position in the global electric vehicle industry supply chain.“Thailand has a favorable business environment,”Zeng responded.“As the location of GAC’s first wholly-owned overseas facility,it was our premier choice.”
基金the National Natural Science Foundation of China(No.52175188)the Key Research and De-velopment Program of Shaanxi Province(No.2023-YBGY-434)+2 种基金the Open Fund of Liaoning Provincial Key Laboratory of Aero-engine Materials Tribology(No.LKLAMTF202301)the Guangdong Basic and Applied Basic Research Foundation(No.2024A1515012378)the Science and Technology on Reactor System Design Tech-nology Laboratory and the Fundamental Research Funds for the Central Universities.
文摘Ensuring the long-term and stable operation of mechanical equipment has been a research emphasis with the development of aerospace and polar exploration,which necessitates the prepared materials with high mechanical strength as well as excellent wear resistance[1].The traditional lubricant is widely acknowledged to be susceptible to evaporation or decomposition under extreme conditions,necessitating the deposition of a protective thin film on critical mechanical parts’surfaces to enhance their mechanical and tribological properties[2,3].
基金supported by the National Natural Science Foundation of China(51975112,52375412)Fundamental Research Funds for Central Universities(N2203011)。
文摘Additive manufacturing provides achievability for the fabrication of bimetallic and multi-material structures;however,the material compatibility and bondability directly affect the parts’formability and final quality.It is essential to understand the underlying printability of different material combinations based on an adapted process.Here,the printability disparities of two common and attractive material combinations(nickel-and iron-based alloys)are evaluated at the macro and micro levels via laser directed energy deposition(DED).The deposition processes were captured using in situ high-speed imaging,and the dissimilarities in melt pool features and track morphology were quantitatively investigated within specific process windows.Moreover,the microstructure diversity of the tracks and blocks processed with varied material pairs was comparatively elaborated and,complemented with the informative multi-physics modeling,the presented non-uniformity in mechanical properties(microhardness)among the heterogeneous material pairs was rationalized.The differences in melt flow induced by the unlike thermophysical properties of the material pairs and the resulting element intermixing and localized re-alloying during solidification dominate the presented dissimilarity in printability among the material combinations.This work provides an in-depth understanding of the phenomenological differences in the deposition of dissimilar materials and aims to guide more reliable DED forming of bimetallic parts.
基金Supported by National Natural Science Foundation of China(Grant No.52005371)Shanghai Municipal Natural Science Foundation of China(Grant No.22ZR1463900)+1 种基金Fundamental Research Funds for the Central Universities of China(Grant No.22120220649)State Key Laboratory of Mechanical System and Vibration of China(Grant No.MSV202318).
文摘An increasing number of researchers have researched fixture layout optimization for thin-walled part assembly during the past decades.However,few papers systematically review these researches.By analyzing existing literature,this paper summarizes the process of fixture layout optimization and the methods applied.The process of optimization is made up of optimization objective setting,assembly variation/deformation modeling,and fixture layout optimization.This paper makes a review of the fixture layout for thin-walled parts according to these three steps.First,two different kinds of optimization objectives are introduced.Researchers usually consider in-plane variations or out-of-plane deformations when designing objectives.Then,modeling methods for assembly variation and deformation are divided into two categories:Mechanism-based and data-based methods.Several common methods are discussed respectively.After that,optimization algorithms are reviewed systematically.There are two kinds of optimization algorithms:Traditional nonlinear programming and heuristic algorithms.Finally,discussions on the current situation are provided.The research direction of fixture layout optimization in the future is discussed from three aspects:Objective setting,improving modeling accuracy and optimization algorithms.Also,a new research point for fixture layout optimization is discussed.This paper systematically reviews the research on fixture layout optimization for thin-walled parts,and provides a reference for future research in this field.
基金supported by the Major Science and Technology Projects in Fujian Province,China(No.2023HZ021005)the State Key Laboratory of Powder Metallurgy,Central South University,China,and Fujian Key Laboratory of Rare-earth Functional Materials,China.
文摘Stereolithography(SLA)combined with a two-step post-processing method“oxidation−reduction”was developed to fabricate pure copper with high complexity.The copper slurries for SLA were prepared,and particularly the influence of volume fraction of copper on the properties of copper slurries was investigated.In the two-step post-treatment process,organics were removed by oxidation and copper powder was oxidized simultaneously,and then the oxidized copper was reduced into highly reactive copper particles,improving the sintering activity of the copper green body and enhancing the relative density of the sintered part.The results show that curing depth of the copper slurries decreased with the increase of volume fraction of copper.The viscosity of the pure copper slurry rises exponentially as the volume fraction of copper exceeded 50%.The highest volume fraction of pure copper slurry for SLA is 55%.The specimens exhibited an increase in hardness and electrical conductivity with the increase of volume fraction of copper.Specifically,the maximum values of hardness and conductivity of samples with 55 vol.%copper were HV 52.7 and 57.1%(IACS),respectively.
文摘Prompt radiation emitted during accelerator operation poses a significant health risk,necessitating a thorough search and securing of hazardous areas prior to initiation.Currently,manual sweep methods are employed.However,the limitations of manual sweeps have become increasingly evident with the implementation of large-scale accelerators.By leveraging advancements in machine vision technology,the automatic identification of stranded personnel in controlled areas through camera imagery presents a viable solution for efficient search and security.Given the criticality of personal safety for stranded individuals,search and security processes must be sufficiently reliable.To ensure comprehensive coverage,180°camera groups were strategically positioned on both sides of the accelerator tunnel to eliminate blind spots within the monitoring range.The YOLOV8 network model was modified to enable the detection of small targets,such as hands and feet,as well as larger targets formed by individuals near the cameras.Furthermore,the system incorporates a pedestrian recognition model that detects human body parts,and an information fusion strategy is used to integrate the detected head,hands,and feet with the identified pedestrians as a cohesive unit.This strategy enhanced the capability of the model to identify pedestrians obstructed by equipment,resulting in a notable improvement in the recall rate.Specifically,recall rates of 0.915 and 0.82were obtained for Datasets 1 and 2,respectively.Although there was a slight decrease in accuracy,it aligned with the intended purpose of the search-and-secure software design.Experimental tests conducted within an accelerator tunnel demonstrated the effectiveness of this approach in achieving reliable recognition outcomes.
基金supported by the Aeronautical Science Foundation of China,No.2023Z0680510022021 Special Scientific Research on Civil Aircraft Project+1 种基金the Natural Science Foundation of China,Nos.61572056 and 61872347the Special Plan for the Development of Distinguished Young Scientists of ISCAS,No.Y8RC535018.
文摘This study proposes an image-based three-dimensional(3D)vector reconstruction of industrial parts that can gener-ate non-uniform rational B-splines(NURBS)surfaces with high fidelity and flexibility.The contributions of this study include three parts:first,a dataset of two-dimensional images is constructed for typical industrial parts,including hex-agonal head bolts,cylindrical gears,shoulder rings,hexagonal nuts,and cylindrical roller bearings;second,a deep learning algorithm is developed for parameter extraction of 3D industrial parts,which can determine the final 3D parameters and pose information of the reconstructed model using two new nets,CAD-ClassNet and CAD-ReconNet;and finally,a 3D vector shape reconstruction of mechanical parts is presented to generate NURBS from the obtained shape parameters.The final reconstructed models show that the proposed approach is highly accurate,efficient,and practical.
