We put forward a new design of a compact beam transport system for intense laser-driven proton therapy,where instead of using conventional pulsed solenoids,our design relies on a helical coil irradiated by a nanosecon...We put forward a new design of a compact beam transport system for intense laser-driven proton therapy,where instead of using conventional pulsed solenoids,our design relies on a helical coil irradiated by a nanosecond laser pulse to generate strong magnetic fields for focusing protons.A pair of dipole magnets and apertures are employed to further filter protons with large divergences and low energies.Our numerical studies combine particle-in-cell simulations for laser-plasma interaction to generate high-energy monoenergetic proton beams,finite element analysis for evaluating the magnetic field distribution inside the coil,and MonteCarlo simulations for beam transport and energy deposition.Our results show that with this design,a spread-out Bragg peak in a range of several centimeters to a deep-seated tumor with a dose of approximately 16.5 cGy and fluctuation around 2% can be achieved.The instantaneous dose rate reaches up to 10^(9)Gy/s,holding the potential for future FLASH radiotherapy research.展开更多
This paper proposes a new element-based multi-material topology optimization algorithm using a single variable for minimizing compliance subject to a mass constraint.A single variable based on the normalized elemental...This paper proposes a new element-based multi-material topology optimization algorithm using a single variable for minimizing compliance subject to a mass constraint.A single variable based on the normalized elemental density is used to overcome the occurrence of meaningless design variables and save computational cost.Different from the traditional material penalization scheme,the algorithm is established on the ordered ersatz material model,which linearly interpolates Young’s modulus for relaxed design variables.To achieve a multi-material design,the multiple floating projection constraints are adopted to gradually push elemental design variables to multiple discrete values.For the convergent element-based solution,the multiple level-set functions are constructed to tentatively extract the smooth interface between two adjacent materials.Some 2D and 3D numerical examples are presented to demonstrate the effectiveness of the proposed algorithm and the possible advantage of the multi-material designs over the traditional solid-void designs.展开更多
Current multiscale topology optimization restricts the solution space by enforcing the use of a few repetitive microstructures that are predetermined,and thus lack the ability for structural concerns like buckling str...Current multiscale topology optimization restricts the solution space by enforcing the use of a few repetitive microstructures that are predetermined,and thus lack the ability for structural concerns like buckling strength,robustness,and multi-functionality.Therefore,in this paper,a new multiscale concurrent topology optimization design,referred to as the self-consistent analysis-based moving morphable component(SMMC)method,is proposed.Compared with the conventional moving morphable component method,the proposed method seeks to optimize both material and structure simultaneously by explicitly designing both macrostructure and representative volume element(RVE)-level microstructures.Numerical examples with transducer design requirements are provided to demonstrate the superiority of the SMMC method in comparison to traditional methods.The proposed method has broad impact in areas of integrated industrial manufacturing design:to solve for the optimized macro and microstructures under the objective function and constraints,to calculate the structural response efficiently using a reduced-order model:self-consistent analysis,and to link the SMMC method to manufacturing(industrial manufacturing or additive manufacturing)based on the design requirements and application areas.展开更多
Reefs are considered to be one of the most abundant and diverse niches in the marine ecosystem, and the study of the composition, distribution, and evolution of reefs over geologic time can provide important clues to ...Reefs are considered to be one of the most abundant and diverse niches in the marine ecosystem, and the study of the composition, distribution, and evolution of reefs over geologic time can provide important clues to understanding contemporaneous marine environmental conditions.展开更多
To enhance the ability of Cyber Physical Social Intelligence(CPSI)to process three-dimensional spatial information,we investigate the problem of object detection in 3D Light laser Detection And Ranging(LiDAR)point clo...To enhance the ability of Cyber Physical Social Intelligence(CPSI)to process three-dimensional spatial information,we investigate the problem of object detection in 3D Light laser Detection And Ranging(LiDAR)point clouds.Traditional point-based processing pipelines typically reduce memory and computational burden by progressively downsampling the input point cloud using task-agnostic random sampling or farthest point sampling.However,these methods often ignore the inherent structural information amongst the points.To address this gap,we introduce a novel structure-aware point cloud pruning technique that utilizes normal vector scoring to capture the critical structural details within point clouds.Furthermore,we implement a Learning-based Structure-Aware Pruning(LSAP)method to avoid the high computational cost associated with top-k selection algorithms.Comprehensive experiments on the ModelNet40 dataset verify the effectiveness of our method.Notably,our LSAP compressed model achieves a remarkable accuracy of 91.2%on ModelNet40 dataset with a pruning rate of 93.5%,attaining up to an 15.9×reduction in FLoating point Operations Per second(FLOPs)with less than 2.3%accuracy degradation.This significantly outperforms baseline pruning methods,delivering an accuracy improvement of 1.3%.展开更多
Urbanization processes affect the ecosystem through alterations in ecological functions and landscape patterns. Currently, analysis of the total ecosystem services value （ESV） has targeted the overall benefits which...Urbanization processes affect the ecosystem through alterations in ecological functions and landscape patterns. Currently, analysis of the total ecosystem services value （ESV） has targeted the overall benefits which human beings obtain from the regional ecosystem but does not generally include information regarding ecological struc- tures and patterns. Therefore, the results cannot reflect the comprehensive state of the local ecosystem. We propose a new, integrative ecosystem quality indicator based on the ESV and landscape metrics for evaluating the quality of the regional ecosystem. We adopted the method of a coupled degree of coordination for evaluating the interrelationship between urbanization and ecosystem quality in Lianyun- gang City from 1985 to 2010. The coupling degree of coordination between urbanization and ecosystem quality showed an inverse U-shaped curve. At the primary stage of urbanization （1985-1995）, the degree of coupling of urbanization and the ecosystem was just barely balanced. From 1995 until 2000, the coupling system reached a balanced condition, in which the urbanization level increased. Since 2000, the urbanization process has accelerated. The coordination between urbanization and the ecosystem achieved the optimum condition in 2005. A turning point appeared at the same time, and the degree of coupling coordination began falling from the optimum. Subsequently, the coupled system once more entered a barely balanced state. Overall, the comprehensive level of ecosystem quality decreased since 1985 and degraded sharply after 2005, suggesting an overall degradation of the local ecosystem quality.展开更多
Marine resources and industry have become one of the most important pillars in economic development all over the world.However,corrosion of materials is always the most serious problem to the infrastructure and equipm...Marine resources and industry have become one of the most important pillars in economic development all over the world.However,corrosion of materials is always the most serious problem to the infrastructure and equipment served in marine environment.Researchers have found that microbiologically influenced corrosion(MIC)and marine bio-fouling are two main mechanisms of marine corrosions due to the complicated marine environment and marine organisms.This article summarized the latest research progress about these two mechanisms and indicated that both MIC and marine bio-fouling are closely related to the biofilms on material surfaces formed by the marine microorganisms and their metabolites.As a result,to prevent the occurrence of MIC and bio-fouling,it is important to control the microorganisms in biofilms or prevent the adhesion and formation of biofilms.The traditional method of using chemical bactericide or antifoulant faces the problems of pollution and microorganism resistance.This article introduced four research approaches about the new tendency of applying new materials and technologies to cooperate with traditional chemicals to achieve better and longer effects with lower environment pollution through synergistic actions.Finally,some future research tendencies were proposed for whole marine anti-corrosion and anti-fouling areas.展开更多
Quantifying and mapping the distribution patterns of ecosystem services can help to ascertain which services should be protected and where investments should be directed to improve synergies and reduce trade- offs. Mo...Quantifying and mapping the distribution patterns of ecosystem services can help to ascertain which services should be protected and where investments should be directed to improve synergies and reduce trade- offs. Moreover, the indicators of urbanization that affect the provision of ecosystem services must be identified to determine which approach to adopt in formulating policies related to these services. This paper presents a case study that maps the distribution of mukiple ecosystem services and analyzes the ways in which they interact. The relationship between the supply of ecosystem services and the socio-economic development in the Taihu Lake Basin of eastern China is also revealed. Results show a significant negative relationship between crop production and tourism income （p 〈 0.005） and a positive relationship between crop production, nutrient retention, and carbon sequestration （p 〈 0.005）. The negative effects of the urbanization process on providing and regulating services are also identified through a comparison of the ecosystem services in large and small cities. Regression analysis was used to compare and elucidate the relative significance of the selected urbanization factors to ecosystem services. The results indicate that urbanization level is the most substantial factor inversely correlated with crop production （R2 = 0.414） and nutrient retention services （R2 = 0.572）. Population density is the most important factor that negatively affects carbon sequestration （R2 = 0.447）. The findings of this study suggest the potential relevance of ecosystem service dynamics to urbanization management and decision making.展开更多
Tissue implant-related infections are among the most serious complications after surgical implantation,including orthopedics and dentistry.Implants with antibacterial ion release systems are efficient and economical a...Tissue implant-related infections are among the most serious complications after surgical implantation,including orthopedics and dentistry.Implants with antibacterial ion release systems are efficient and economical antibiotic substitutes to fight against bacterial infections.However,the excessive amount of released antibacterial ions may cause biological toxicity while killing bacteria.This raises a fundamental issue on how to properly control the amounts of ions and their efficacy.Here,we develop low-dose antibacterial ions-incorporated ferroelectric implants(copper-doped potassium sodium niobate,K0.5Na0.5NbO3-Cu,KNNCu)whose surface potential can be tuned via external polarization.The released Cu2+ions can be targeted to bacteria via endogenous electric field(EEF)between KNNCu implants and negatively charged bacteria.Intriguingly,the antibacterial efficacy of the implants is determined by the amount of Cu^2+ions that reaches bacteria,instead of the total amount of released Cu2+ions.The amount of Cu2+ions reaching bacteria from the high-surface-potential implant is 2.4 times that from the lowsurface-potential implant within 12 h,resulting in the increased antibacterial ratio from about 65%to 100%,while remaining low cell toxicity.This work provides insights into the specific role of the EEF in guiding mass transport between charged materials and living organisms,and a new perspective for the design of high-performance antibacterial biomaterials.展开更多
Challenge 3 of the 2022 NIST additive manufacturing benchmark(AM Bench)experiments asked modelers to submit predictions for solid cooling rate,liquid cooling rate,time above melt,and melt pool geometry for single and ...Challenge 3 of the 2022 NIST additive manufacturing benchmark(AM Bench)experiments asked modelers to submit predictions for solid cooling rate,liquid cooling rate,time above melt,and melt pool geometry for single and multiple track laser powder bed fusion process using moving lasers.An in-house developed Additive Manufacturing Computational Fluid Dynamics code(AM-CFD)combined with a cylindrical heat source is implemented to accurately predict these experiments.Heuristic heat source calibration is proposed relating volumetric energy density(ψ)based on experiments available in the literature.The parameters of the heat source of the computational model are initially calibrated based on a Higher Order Proper Generalized Decomposition-(HOPGD)based surrogate model.The prediction using the calibrated heat source agrees quantitatively with NIST measurements for different process conditions(laser spot diameter,laser power,and scan speed).A scaling law based on keyhole formation is also utilized in calibrating the parameters of the cylindrical heat source and predicting the challenge experiments.In addition,an improvement on the heat source model is proposed to relate the Volumetric Energy Density(VED_(σ))to the melt pool aspect ratio.The model shows further improvement in the prediction of the experimental measurements for the melt pool,including cases at higher VED_(σ).Overall,it is concluded that the appropriate selection of laser heat source parameterization scheme along with the heat source model is crucial in the accurate prediction of melt pool geometry and thermal measurements while bypassing the expensive computational simulations that consider increased physics equations.展开更多
基金supported by the National Key R&D Program of China(Nos.2022YFA1603200 and 2022YFA1603201)National Natural Science Foundation of China(Nos.12135001,11921006,12475243 and 11825502)+1 种基金Strategic Priority Research Program of CAS(No.XDA25050900)support from the National Natural Science Funds for Distinguished Young Scholar(No.11825502)。
文摘We put forward a new design of a compact beam transport system for intense laser-driven proton therapy,where instead of using conventional pulsed solenoids,our design relies on a helical coil irradiated by a nanosecond laser pulse to generate strong magnetic fields for focusing protons.A pair of dipole magnets and apertures are employed to further filter protons with large divergences and low energies.Our numerical studies combine particle-in-cell simulations for laser-plasma interaction to generate high-energy monoenergetic proton beams,finite element analysis for evaluating the magnetic field distribution inside the coil,and MonteCarlo simulations for beam transport and energy deposition.Our results show that with this design,a spread-out Bragg peak in a range of several centimeters to a deep-seated tumor with a dose of approximately 16.5 cGy and fluctuation around 2% can be achieved.The instantaneous dose rate reaches up to 10^(9)Gy/s,holding the potential for future FLASH radiotherapy research.
基金This work was supported by Hunan Provincial Innovation Foundation for Postgraduate(CX20190278)FJUT Scientific Research Foundation(GY-Z17015)Open Fund of Fujian Key Laboratory of Automotive Electronics and Electric Drive(KF-X19001).
文摘This paper proposes a new element-based multi-material topology optimization algorithm using a single variable for minimizing compliance subject to a mass constraint.A single variable based on the normalized elemental density is used to overcome the occurrence of meaningless design variables and save computational cost.Different from the traditional material penalization scheme,the algorithm is established on the ordered ersatz material model,which linearly interpolates Young’s modulus for relaxed design variables.To achieve a multi-material design,the multiple floating projection constraints are adopted to gradually push elemental design variables to multiple discrete values.For the convergent element-based solution,the multiple level-set functions are constructed to tentatively extract the smooth interface between two adjacent materials.Some 2D and 3D numerical examples are presented to demonstrate the effectiveness of the proposed algorithm and the possible advantage of the multi-material designs over the traditional solid-void designs.
文摘Current multiscale topology optimization restricts the solution space by enforcing the use of a few repetitive microstructures that are predetermined,and thus lack the ability for structural concerns like buckling strength,robustness,and multi-functionality.Therefore,in this paper,a new multiscale concurrent topology optimization design,referred to as the self-consistent analysis-based moving morphable component(SMMC)method,is proposed.Compared with the conventional moving morphable component method,the proposed method seeks to optimize both material and structure simultaneously by explicitly designing both macrostructure and representative volume element(RVE)-level microstructures.Numerical examples with transducer design requirements are provided to demonstrate the superiority of the SMMC method in comparison to traditional methods.The proposed method has broad impact in areas of integrated industrial manufacturing design:to solve for the optimized macro and microstructures under the objective function and constraints,to calculate the structural response efficiently using a reduced-order model:self-consistent analysis,and to link the SMMC method to manufacturing(industrial manufacturing or additive manufacturing)based on the design requirements and application areas.
文摘Reefs are considered to be one of the most abundant and diverse niches in the marine ecosystem, and the study of the composition, distribution, and evolution of reefs over geologic time can provide important clues to understanding contemporaneous marine environmental conditions.
基金supported by the Young Scientists Fund of the National Natural Science Foundation of China(No.62302529)the National Natural Science Foundation of China(No.62302527)+1 种基金the Hunan Provincial Natural Science Foundation of China(No.2023JJ40770)the Changsha Municipal Natural Science Foundation(No.kq2208290).
文摘To enhance the ability of Cyber Physical Social Intelligence(CPSI)to process three-dimensional spatial information,we investigate the problem of object detection in 3D Light laser Detection And Ranging(LiDAR)point clouds.Traditional point-based processing pipelines typically reduce memory and computational burden by progressively downsampling the input point cloud using task-agnostic random sampling or farthest point sampling.However,these methods often ignore the inherent structural information amongst the points.To address this gap,we introduce a novel structure-aware point cloud pruning technique that utilizes normal vector scoring to capture the critical structural details within point clouds.Furthermore,we implement a Learning-based Structure-Aware Pruning(LSAP)method to avoid the high computational cost associated with top-k selection algorithms.Comprehensive experiments on the ModelNet40 dataset verify the effectiveness of our method.Notably,our LSAP compressed model achieves a remarkable accuracy of 91.2%on ModelNet40 dataset with a pruning rate of 93.5%,attaining up to an 15.9×reduction in FLoating point Operations Per second(FLOPs)with less than 2.3%accuracy degradation.This significantly outperforms baseline pruning methods,delivering an accuracy improvement of 1.3%.
基金We appreciate the contributions made by the reviewers to improve the paper＇s quality. This study was financially supported by the National Natural Science Foundation of China （Grant No. 41271008）, the Fundamental Research Funds for the Central Universities of China （20720150074）, the Key Laboratory of the Coastal Zone Exploitation and Protection, Ministry of Land and Resource of China （2013CZEPK07）, Innovation Fund for Ph.D Students of Jiangsu Province （Grant No. CXLX12- 0057） and Research Project of the State Key Laboratory of Pollution Control and Resources Reuse.
文摘Urbanization processes affect the ecosystem through alterations in ecological functions and landscape patterns. Currently, analysis of the total ecosystem services value （ESV） has targeted the overall benefits which human beings obtain from the regional ecosystem but does not generally include information regarding ecological struc- tures and patterns. Therefore, the results cannot reflect the comprehensive state of the local ecosystem. We propose a new, integrative ecosystem quality indicator based on the ESV and landscape metrics for evaluating the quality of the regional ecosystem. We adopted the method of a coupled degree of coordination for evaluating the interrelationship between urbanization and ecosystem quality in Lianyun- gang City from 1985 to 2010. The coupling degree of coordination between urbanization and ecosystem quality showed an inverse U-shaped curve. At the primary stage of urbanization （1985-1995）, the degree of coupling of urbanization and the ecosystem was just barely balanced. From 1995 until 2000, the coupling system reached a balanced condition, in which the urbanization level increased. Since 2000, the urbanization process has accelerated. The coordination between urbanization and the ecosystem achieved the optimum condition in 2005. A turning point appeared at the same time, and the degree of coupling coordination began falling from the optimum. Subsequently, the coupled system once more entered a barely balanced state. Overall, the comprehensive level of ecosystem quality decreased since 1985 and degraded sharply after 2005, suggesting an overall degradation of the local ecosystem quality.
基金supported by the National Key R&D Program of China(2018YFC1105304)the National Natural Science Foundation of China(Grant Nos.51702106)+1 种基金the Natural Science Foundation of Guangdong Province(2016A030308014)China Postdoctoral Science Foundation(Grant Nos.2017M622686,2018T110865).
文摘Marine resources and industry have become one of the most important pillars in economic development all over the world.However,corrosion of materials is always the most serious problem to the infrastructure and equipment served in marine environment.Researchers have found that microbiologically influenced corrosion(MIC)and marine bio-fouling are two main mechanisms of marine corrosions due to the complicated marine environment and marine organisms.This article summarized the latest research progress about these two mechanisms and indicated that both MIC and marine bio-fouling are closely related to the biofilms on material surfaces formed by the marine microorganisms and their metabolites.As a result,to prevent the occurrence of MIC and bio-fouling,it is important to control the microorganisms in biofilms or prevent the adhesion and formation of biofilms.The traditional method of using chemical bactericide or antifoulant faces the problems of pollution and microorganism resistance.This article introduced four research approaches about the new tendency of applying new materials and technologies to cooperate with traditional chemicals to achieve better and longer effects with lower environment pollution through synergistic actions.Finally,some future research tendencies were proposed for whole marine anti-corrosion and anti-fouling areas.
文摘Quantifying and mapping the distribution patterns of ecosystem services can help to ascertain which services should be protected and where investments should be directed to improve synergies and reduce trade- offs. Moreover, the indicators of urbanization that affect the provision of ecosystem services must be identified to determine which approach to adopt in formulating policies related to these services. This paper presents a case study that maps the distribution of mukiple ecosystem services and analyzes the ways in which they interact. The relationship between the supply of ecosystem services and the socio-economic development in the Taihu Lake Basin of eastern China is also revealed. Results show a significant negative relationship between crop production and tourism income （p 〈 0.005） and a positive relationship between crop production, nutrient retention, and carbon sequestration （p 〈 0.005）. The negative effects of the urbanization process on providing and regulating services are also identified through a comparison of the ecosystem services in large and small cities. Regression analysis was used to compare and elucidate the relative significance of the selected urbanization factors to ecosystem services. The results indicate that urbanization level is the most substantial factor inversely correlated with crop production （R2 = 0.414） and nutrient retention services （R2 = 0.572）. Population density is the most important factor that negatively affects carbon sequestration （R2 = 0.447）. The findings of this study suggest the potential relevance of ecosystem service dynamics to urbanization management and decision making.
基金supported by the National Key R&D Program of China(2018YFC1105304 and 2018YFC1105301)the National Natural Science Foundation of China(51772106,31771080,51702104,51672088 and 31700880)+2 种基金the Natural Science Foundation of Guangdong Province(2016A030308014)the Joint Funds of the National Natural Science Foundation of China(U1501245)the Science and Technology Innovation Team Project of Foshan(2015IT100062)。
文摘Tissue implant-related infections are among the most serious complications after surgical implantation,including orthopedics and dentistry.Implants with antibacterial ion release systems are efficient and economical antibiotic substitutes to fight against bacterial infections.However,the excessive amount of released antibacterial ions may cause biological toxicity while killing bacteria.This raises a fundamental issue on how to properly control the amounts of ions and their efficacy.Here,we develop low-dose antibacterial ions-incorporated ferroelectric implants(copper-doped potassium sodium niobate,K0.5Na0.5NbO3-Cu,KNNCu)whose surface potential can be tuned via external polarization.The released Cu2+ions can be targeted to bacteria via endogenous electric field(EEF)between KNNCu implants and negatively charged bacteria.Intriguingly,the antibacterial efficacy of the implants is determined by the amount of Cu^2+ions that reaches bacteria,instead of the total amount of released Cu2+ions.The amount of Cu2+ions reaching bacteria from the high-surface-potential implant is 2.4 times that from the lowsurface-potential implant within 12 h,resulting in the increased antibacterial ratio from about 65%to 100%,while remaining low cell toxicity.This work provides insights into the specific role of the EEF in guiding mass transport between charged materials and living organisms,and a new perspective for the design of high-performance antibacterial biomaterials.
基金the NIST AM Bench organizing committee for their high-quality experimental datasets and the United States National Science Foundation(NSF)funding under Grant No.CMMI-1934367 and Center for Hierarchical Material Design(CHiMaD).
文摘Challenge 3 of the 2022 NIST additive manufacturing benchmark(AM Bench)experiments asked modelers to submit predictions for solid cooling rate,liquid cooling rate,time above melt,and melt pool geometry for single and multiple track laser powder bed fusion process using moving lasers.An in-house developed Additive Manufacturing Computational Fluid Dynamics code(AM-CFD)combined with a cylindrical heat source is implemented to accurately predict these experiments.Heuristic heat source calibration is proposed relating volumetric energy density(ψ)based on experiments available in the literature.The parameters of the heat source of the computational model are initially calibrated based on a Higher Order Proper Generalized Decomposition-(HOPGD)based surrogate model.The prediction using the calibrated heat source agrees quantitatively with NIST measurements for different process conditions(laser spot diameter,laser power,and scan speed).A scaling law based on keyhole formation is also utilized in calibrating the parameters of the cylindrical heat source and predicting the challenge experiments.In addition,an improvement on the heat source model is proposed to relate the Volumetric Energy Density(VED_(σ))to the melt pool aspect ratio.The model shows further improvement in the prediction of the experimental measurements for the melt pool,including cases at higher VED_(σ).Overall,it is concluded that the appropriate selection of laser heat source parameterization scheme along with the heat source model is crucial in the accurate prediction of melt pool geometry and thermal measurements while bypassing the expensive computational simulations that consider increased physics equations.
文摘This article discusses the definitions,classifications and features of consonants and vowels by listing different varieties of languages as examples.
