In this work, a survey of companies has been produc ed from a questionnaire and in-depth inter-views. The aimof the paper is to give a current view of the use of DES (Discrete- Event Simulation) in the indust ry. The ...In this work, a survey of companies has been produc ed from a questionnaire and in-depth inter-views. The aimof the paper is to give a current view of the use of DES (Discrete- Event Simulation) in the indust ry. The companies have been selected in a wide range in e.g. size, capital turno ver and employees. The survey was restricted to Sweden, although the results may be applicable to other countries with similar industrial structure. Some of the companies investigated are also multinational with branches around the world. T o illustrate the differences in production systems different sectors have be en investigated, e.g. the manufacturing industry and energy sector. The manufact uring systems generally differ in that the energy sector is more known for high reliability in their systems and the manufacturing sector tends to work more wit h lean production. Previous surveys of manufacturing efficiency illustrate different aspects. Accor ding to one survey, more than one-third (34%) of the disturbances in two countr ies (the U.S. and Finland) were mainly caused by design-based errors and flaws. The survey also showed the scope of safety problems experienced in the implemen tation and use of flexible manufacturing systems (Jrvinen et al., 1996). Another survey in Germany reports a gap between users and non-users of DES. Man y companies that are not familiar with simulation are not aware of its benefits. The study suggested integrating simulation into the planning processes as a reg ular tool. So far, DES is mostly used in system planning, resource planning and scheduling and production planning (Hirschberg & Heitmann, 1997). The disposition of the accomplished questionnaire had been multiple-choice ques tions in a strict order. The respondents gave their views on what the interviewe r considered relevant for the survey. The questionnaire was mailed to 220 person s in May 2001; a second round for unanswered surveys was dispatched in August 20 01. Replies came from 114 respondents; thus, the reply rate to all questionnaire s sent out was 52%. The replies came in from 80 different companies. Questionswere raised regarding what kinds of decisions are taken from a simulation projec t and questions were also asked regarding the tool itself. Some common problems encountered based on the authors’ knowledge were asked in the questionnaire. The questions were sent to those who had reasonable knowledge of how to work with D ES. Supplementary in-depth interviews were also accomplished. On the question if DES facilitates the decision-making process 79% of totally 3 8 answered to a very large or a large extent. Regarding the question if DES is a useful tool for measuring the availability of equipment for example system verification 73% of 33 responded to a very large or a large extent. A majority o f the respondents genuinely see an advantage with the use of simulation, which i s an important result from the study. The cost reduction aspect of the productio n is also an advantage of DES. On the question eight answered to a very large ex tent and 23 to a large extent of total 39 replies. The question demonstrates tha t the results of a simulation model are indeed used in the real world. Finally, in the question of DES is used for staffing it is indicated that it is not so co mmonly used as for other functions asked for. The staffing issue requires good k nowledge about time measurement of manual labor. The option, however, to include manual work in a simulation model is in many programs extensive and must be a v aluable option to evaluate work intensive parts of production lines and their im provement. To conclude, it could be mentioned that DES is a tool with potential. The use is increasing and 12 of 80 companies investigated in Sweden 2001 are using it, an increase compared to previous stud-ies. Of those 12 companies, four are using t he tool to a large extent. The main advantage according to the survey beside the visualization part is that the knowledge about a system is investigated and doc umented.展开更多
The Riyadh metro project is one of the current megaprojects that aim to improve the transit systems in Saudi Arabia.It consists of several metro lines with a total length of 176 km and 85 stations.The viaducts are con...The Riyadh metro project is one of the current megaprojects that aim to improve the transit systems in Saudi Arabia.It consists of several metro lines with a total length of 176 km and 85 stations.The viaducts are considered as one of the main construction elements in the metro lines.Four methods for viaducts construction have been used in the Riyadh metro project:precast beam,full span launching method,cast on-site,and segment method(precast segment method and BCM(balanced cantilever method)).The viaducts work consumes a large portion of a project’s time and cost.Furthermore,the competitive nature of the construction industry increases the need to improve the efficiency of construction performance.Accordingly,this paper takes the initial steps toward increasing the efficiency of viaduct construction methods through simulation.Simulation of construction processes provides a systematic tool that can be used for determining the resources,time,and cost of these processes.The simulation processes should focus on the main activities affecting this element’s execution for viaducts construction,such as segment storage,handling,transporting,and installation.This study highlights the viaducts construction methods and develops general discrete-event simulation models for the most commonly used viaducts construction methods in the Riyadh metro using AnyLogic simulation software.The simulation models visualize and capture the interaction between the different activities and resources in a viaduct construction.Consequently,the construction drawbacks can be identified.Furthermore,the simulation model can be manipulated by adding assumptions to develop more efficient construction methods in terms of time and cost in such projects.展开更多
The goal of this paper is to provide an approach to investigate the variation of fiber quantity in a certain cross-section of the drafting zone. This model with discrete-event simulation( DES)method was presented to s...The goal of this paper is to provide an approach to investigate the variation of fiber quantity in a certain cross-section of the drafting zone. This model with discrete-event simulation( DES)method was presented to simulate the dynamic drafting process. This model described the behavior of individual fibers,which was divided into four phases and simulated by corresponding modules. Three sets of processing conditions in industry were simulated and demonstrated the applications of this model. The comparison between experiments and simulation results could also validate this model. This model could be used to simulate various drafting process with appropriate drafting settings.展开更多
Object-oriented world-view provides a natural and powerful paradignl for expressing system elements and their dynamic behaviour for discrete-event simulation. Simulation gives the critical ability to study the dynamic...Object-oriented world-view provides a natural and powerful paradignl for expressing system elements and their dynamic behaviour for discrete-event simulation. Simulation gives the critical ability to study the dynamic behaviour of the models that are defined with object-voriented means. This paper first examines the ways of applying the object-oriented world-view to three major discrete simulation modelling approaches, then considers the process and merits of object-oriented simulation modelling.展开更多
Wire arc additive manufacturing(WAAM)has emerged as a promising approach for fabricating large-scale components.However,conventional WAAM still faces challenges in optimizing microstructural evolution,minimizing addit...Wire arc additive manufacturing(WAAM)has emerged as a promising approach for fabricating large-scale components.However,conventional WAAM still faces challenges in optimizing microstructural evolution,minimizing additive-induced defects,and alleviating residual stress and deformation,all of which are critical for enhancing the mechanical performance of the manufactured parts.Integrating interlayer friction stir processing(FSP)into WAAM significantly enhances the quality of deposited materials.However,numerical simulation research focusing on elucidating the associated thermomechanical coupling mechanisms remains insufficient.A comprehensive numerical model was developed to simulate the thermomechanical coupling behavior in friction stir-assisted WAAM.The influence of post-deposition FSP on the coupled thermomechanical response of the WAAM process was analyzed quantitatively.Moreover,the residual stress distribution and deformation behavior under both single-layer and multilayer deposition conditions were investigated.Thermal analysis of different deposition layers in WAAM and friction stir-assisted WAAM was conducted.Results show that subsequent layer deposition induces partial remelting of the previously solidified layer,whereas FSP does not cause such remelting.Furthermore,thermal stress and deformation analysis confirm that interlayer FSP effectively mitigates residual stresses and distortion in WAAM components,thereby improving their structural integrity and mechanical properties.展开更多
The F_(1)-ATPase and V_(1)-ATPase are rotary biomotors.Alignment of their amino acid sequences,which originate from bovine heart mitochondria(1BMF)and Enterococcus hirae(3VR6),respectively,demonstrates that the segmen...The F_(1)-ATPase and V_(1)-ATPase are rotary biomotors.Alignment of their amino acid sequences,which originate from bovine heart mitochondria(1BMF)and Enterococcus hirae(3VR6),respectively,demonstrates that the segment forming the ATP catalytic pocket is highly conserved.Single-molecule experiments,however,have revealed subtle differences in efficiency between the F_(1) and V_(1) motors.Here,we perform both atomistic and coarse-grained molecular dynamics simulations to investigate the mechanochemical coupling and coordination in F_(1) and V_(1) ATPase.Our results show that the correlation between conformational changes in F_(1) is stronger than that in V_(1),indicating that the mechanochemical coupling in F_(1) is tighter than in V_(1).Moreover,the unidirectional rotation of F_(1) is more processive than that of V_(1),which accounts for the higher efficiency observed in F_(1) and explains the occasional backward steps detected in single-molecule experiments on V_(1).展开更多
The rapid advancement of machine learning based tight-binding Hamiltonian(MLTB)methods has opened new avenues for efficient and accurate electronic structure simulations,particularly in large-scale systems and long-ti...The rapid advancement of machine learning based tight-binding Hamiltonian(MLTB)methods has opened new avenues for efficient and accurate electronic structure simulations,particularly in large-scale systems and long-time scenarios.This review begins with a concise overview of traditional tight-binding(TB)models,including both(semi-)empirical and first-principles approaches,establishing the foundation for understanding MLTB developments.We then present a systematic classification of existing MLTB methodologies,grouped into two major categories:direct prediction of TB Hamiltonian elements and inference of empirical parameters.A comparative analysis with other ML-based electronic structure models is also provided,highlighting the advancement of MLTB approaches.Finally,we explore the emerging MLTB application ecosystem,highlighting how the integration of MLTB models with a diverse suite of post-processing tools from linear-scaling solvers to quantum transport frameworks and molecular dynamics interfaces is essential for tackling complex scientific problems across different domains.The continued advancement of this integrated paradigm promises to accelerate materials discovery and open new frontiers in the predictive simulation of complex quantum phenomena.展开更多
Vitrimers belong to a class of polymeric materials capable of bond exchange reactions,showing great promise for environmental protection and sustainable development.However,studies on the coupling mechanism between th...Vitrimers belong to a class of polymeric materials capable of bond exchange reactions,showing great promise for environmental protection and sustainable development.However,studies on the coupling mechanism between the bond exchange kinetics and segmental dynamics near the glass transition temperature(T_(g))remain scarce.Herein,we employed molecular dynamics simulations to investigate the dynamic heterogeneity of the segment motion and bond exchange in vitrimers.The simulation results revealed that the bond exchange energy barrier exerts a much stronger influence on the bond exchange kinetics than on the segmental dynamics.At lower temperatures,slower segmental relaxation further constraind the bond exchange rate.Additionally,increasing the bond exchange energy barrier markedly enhanced the dynamic heterogeneity of segment motion.A close correlation was observed between heterogeneity and bond exchange.This study elucidated the coupling mechanism between bond exchange and segmental dynamics at the molecular scale,thereby providing a theoretical basis for designing vitrimer materials with tunable dynamic properties.展开更多
In federated learning,backdoor attacks have become an important research topic with their wide application in processing sensitive datasets.Since federated learning detects or modifies local models through defense mec...In federated learning,backdoor attacks have become an important research topic with their wide application in processing sensitive datasets.Since federated learning detects or modifies local models through defense mechanisms during aggregation,it is difficult to conduct effective backdoor attacks.In addition,existing backdoor attack methods are faced with challenges,such as low backdoor accuracy,poor ability to evade anomaly detection,and unstable model training.To address these challenges,a method called adaptive simulation backdoor attack(ASBA)is proposed.Specifically,ASBA improves the stability of model training by manipulating the local training process and using an adaptive mechanism,the ability of the malicious model to evade anomaly detection by combing large simulation training and clipping,and the backdoor accuracy by introducing a stimulus model to amplify the impact of the backdoor in the global model.Extensive comparative experiments under five advanced defense scenarios show that ASBA can effectively evade anomaly detection and achieve high backdoor accuracy in the global model.Furthermore,it exhibits excellent stability and effectiveness after multiple rounds of attacks,outperforming state-of-the-art backdoor attack methods.展开更多
UHMWPE fibers exhibit impressive modulus and strength,but they have not reached their theoretical limits.Researchers focus on molecular weight,orientation,and crystallinity of UHMWPE,yet their contributions to mechani...UHMWPE fibers exhibit impressive modulus and strength,but they have not reached their theoretical limits.Researchers focus on molecular weight,orientation,and crystallinity of UHMWPE,yet their contributions to mechanical properties are unclear.Molecular dynamics simulations are valuable but often limited by computational constraints.Our aim is to simulate higher molecular weights to better represent real UHMWPE fibers.We used Packmol and Polyply methodologies to construct PE systems,with Polyply reproducing more reasonable properties of UHMWPE fibers.Additionally,tensile simulations showed that orientation and crystallinity greatly impact Young's modulus more than molecular weight.Energy decomposition indicated that higher molecular weights lead to covalent bonds that can withstand more energy during stretching,thus increasing breaking strength.Combining simulations with machine learning,we found that orientation has the most significant impact on Young's modulus,contributing 60%,and molecular weight plays the most crucial role in determining the breaking strength,accounting for 65%.This study provides a theoretical basis and guidelines for enhancing UHMWPE's modulus and strength.展开更多
With the rapid proliferation of electric vehicles,their charging loads pose new challenges to power grid stability and operational efficiency.To address this,this study employs a Monte Carlo simulation model to analyz...With the rapid proliferation of electric vehicles,their charging loads pose new challenges to power grid stability and operational efficiency.To address this,this study employs a Monte Carlo simulation model to analyze the charging load characteristics of six battery electric vehicle categories in Hebei Province,leveraging multi-source probabilistic distribution data under typical operational scenarios.The findings reveal that electric vehicle charging loads are primarily concentrated during midday and nighttime periods,with significant load fluctuations exerting substantial pressure on the grid.In response,this paper proposes strategic interventions including optimized charging infrastructure planning,time-of-use electricity pricing mechanisms,and smart charging technologies to balance grid loads.The results provide a theoretical foundation for electric vehicle load forecasting,smart grid dispatching,and vehicle-grid integration,thereby enhancing grid operational efficiency and sustainability.展开更多
In recent years,three-dimensional reconstruction technologies that employ multiple cameras have continued to evolve significantly,enabling remote collaboration among users in extended Reality(XR)environments.In additi...In recent years,three-dimensional reconstruction technologies that employ multiple cameras have continued to evolve significantly,enabling remote collaboration among users in extended Reality(XR)environments.In addition,methods for deploying multiple cameras for motion capture of users(e.g.,performers)are widely used in computer graphics.As the need to minimize and optimize the number of cameras grows to reduce costs,various technologies and research approaches focused on Optimal Camera Placement(OCP)are continually being proposed.However,as most existing studies assume homogeneous camera setups,there is a growing demand for studies on heterogeneous camera setups.For instance,technical demands keep emerging in scenarios with minimal camera configurations,especially regarding cost factors,the physical placement of cameras given the spatial structure,and image capture strategies for heterogeneous cameras,such as high-resolution RGB cameras and depth cameras.In this study,we propose a pre-visualization and simulation method for the optimal placement of heterogeneous cameras in XR environments,accounting for both the specifications of heterogeneous cameras(e.g.,field of view)and the physical configuration(e.g.,wall configuration)in real-world spaces.The proposed method performs a visibility analysis of cameras by considering each camera’s field-of-view volume,resolution,and unique characteristics,along with physicalspace constraints.This approach enables the optimal position and rotation of each camera to be recommended,along with the minimum number of cameras required.In the results of our study conducted in heterogeneous camera combinations,the proposed method achieved 81.7%~82.7%coverage of the target visual information using only 2~3 cameras.In contrast,single(or homogeneous)-typed cameras were required to use 11 cameras for 81.6%coverage.Accordingly,we found that camera deployment resources can be reduced with the proposed approaches.展开更多
Because of the developed surface of the Triply PeriodicMinimumSurface(TPMS)structures,polylactide(PLA)products with a TPMS structure are thought to be promising bio soluble implants with the potential for targeted dru...Because of the developed surface of the Triply PeriodicMinimumSurface(TPMS)structures,polylactide(PLA)products with a TPMS structure are thought to be promising bio soluble implants with the potential for targeted drug delivery.For implants,mechanical properties are key performance characteristics,so understanding the deformation and failure mechanisms is essential for selecting the appropriate implant structure.The deformation and fracture processes in PLA samples with different interior architectures have been studied through computer simulation and experimental research.Two TPMS topologies,the Schwarz Diamond and Gyroid architectures,were used for the sample construction by 3D printing.ANSYS software was utilized to simulate compressive deformation.It was found that under the same load,the vonMises stresses in the Gyroid structure are higher than those in the Schwartz Diamond structure,which was associated with the different orientations of the cells in the studied structures in relation to the direction of the loading axis.The deformation process occurs in the local regions of the studied TPMS structures.Maximum von Mises stresses were observed in the vertical parts of the structures oriented along the load direction.It was found that,unlike the Gyroid,the Schwartz Diamond structure contains a frame that forms unique stiffening ribs,which ensures the redistribution of the load under the vertical loading direction.An analysis of the mechanical characteristics of PLA samples with the Schwartz Diamond and Gyroid structures produced by the Fused Deposition Modeling(FDM)method was correlated with computer simulation.The Schwarz Diamond-type structure was shown to have a higher absorption energy than the Gyroid one.A study of the fracture in PLA samples with various cell sizes revealed a particular feature related to the samples’periodic surface topology and the 3D printing process.Scanning electron microscopic(SEM)studies of the samples deformed by compression showed thatwith an increase in the density of the samples,the failure mechanism changes from ductile to quasi-brittle due to the complex participation of both cell deformation and fiber deformation.展开更多
The effect of temperature on molten zone length was investigated through simulation to optimize the control of molten zone length during the experimental process. The temperature gradient distribution within the molte...The effect of temperature on molten zone length was investigated through simulation to optimize the control of molten zone length during the experimental process. The temperature gradient distribution within the molten zone during zone refining was simulated using COMSOL Multiphysics software and experimentally validated. The simulated molten zone length showed good agreement with the actual measured length. The experimental study of tellurium purification by zone refining was conducted under the following conditions: three passes of zone refining, a hydrogen flow rate of 0.5 L/min, and molten zone movement speeds of 0.5 and 1.0 mm/min. The results demonstrated that the removal efficiencies of impurities such as Ca and Cu exceeded 95%, while the removal efficiency of phosphorus (P) reached over 70%. And the purity of tellurium reached 6N.展开更多
Ice crystal icing is an important cause of accidents in aircraft engines.Ice formation in aircraft engines can cause internal blades to freeze,affecting the quality of the air flow field and blocking the flow path.On ...Ice crystal icing is an important cause of accidents in aircraft engines.Ice formation in aircraft engines can cause internal blades to freeze,affecting the quality of the air flow field and blocking the flow path.On the other hand,the entry of ice crystal particles into the combustion chamber can cause a decrease in temperature or even flameout,leading to engine surge or shutdown.Therefore,it is necessary to conduct multiphase flow tests on ice crystals for aircraft components such as aircraft engines.Conducting ice crystal multiphase flow tests on aircraft is an effective research method,but it requires the construction of an ice crystal multiphase flow test platform that meets relevant technical requirements.The paper focuses on the relevant experimental requirements and combines wind tunnel test structures to conduct multiphase flow numerical simulations on various forms of jet pipelines,obtaining particle motion distribution results.After comparison,the optimal form of jet structure is obtained,providing the best selection scheme for the design of relevant wind tunnel structures.展开更多
Centrifugal casting of ductile iron pipe is a high-temperature,semi-continuous production process.However,conducting laboratory research on the solidification process of centrifugal casting of ductile iron pipe presen...Centrifugal casting of ductile iron pipe is a high-temperature,semi-continuous production process.However,conducting laboratory research on the solidification process of centrifugal casting of ductile iron pipe presents significant challenges.In this study,a novel research method was introduced for investigating the solidification process of ductile iron pipe,namely thermal simulation of ductile iron pipe.Comparative research was conducted on the microstructure and properties of the thermal simulation sample and the ductile iron pipe.The findings indicate that the thermal simulation sample and ductile iron pipe exhibit good heat transfer similarity and microstructure similarity.The difference of cooling rate between thermal simulation sample and ductile pipe is less than 0.24℃·s^(-1),and the difference of microstructure content of free cementite,ferrite,and pearlite is less than 5%.The tensile strength of annealed ductile iron pipe is 466 MPa,with an elongation of 16.1%and a Brinell hardness of 156.5 HBW.In comparison,the tensile strength of annealed thermal simulation sample is 482.0 MPa,with an elongation of 15.5%and a Brinell hardness of 159.0 HBW.These results suggest that the thermal simulation experimental research method is both scientific and feasible,offering an objective,reliable,and cost-effective approach to laboratory research on ductile iron pipe.展开更多
文摘In this work, a survey of companies has been produc ed from a questionnaire and in-depth inter-views. The aimof the paper is to give a current view of the use of DES (Discrete- Event Simulation) in the indust ry. The companies have been selected in a wide range in e.g. size, capital turno ver and employees. The survey was restricted to Sweden, although the results may be applicable to other countries with similar industrial structure. Some of the companies investigated are also multinational with branches around the world. T o illustrate the differences in production systems different sectors have be en investigated, e.g. the manufacturing industry and energy sector. The manufact uring systems generally differ in that the energy sector is more known for high reliability in their systems and the manufacturing sector tends to work more wit h lean production. Previous surveys of manufacturing efficiency illustrate different aspects. Accor ding to one survey, more than one-third (34%) of the disturbances in two countr ies (the U.S. and Finland) were mainly caused by design-based errors and flaws. The survey also showed the scope of safety problems experienced in the implemen tation and use of flexible manufacturing systems (Jrvinen et al., 1996). Another survey in Germany reports a gap between users and non-users of DES. Man y companies that are not familiar with simulation are not aware of its benefits. The study suggested integrating simulation into the planning processes as a reg ular tool. So far, DES is mostly used in system planning, resource planning and scheduling and production planning (Hirschberg & Heitmann, 1997). The disposition of the accomplished questionnaire had been multiple-choice ques tions in a strict order. The respondents gave their views on what the interviewe r considered relevant for the survey. The questionnaire was mailed to 220 person s in May 2001; a second round for unanswered surveys was dispatched in August 20 01. Replies came from 114 respondents; thus, the reply rate to all questionnaire s sent out was 52%. The replies came in from 80 different companies. Questionswere raised regarding what kinds of decisions are taken from a simulation projec t and questions were also asked regarding the tool itself. Some common problems encountered based on the authors’ knowledge were asked in the questionnaire. The questions were sent to those who had reasonable knowledge of how to work with D ES. Supplementary in-depth interviews were also accomplished. On the question if DES facilitates the decision-making process 79% of totally 3 8 answered to a very large or a large extent. Regarding the question if DES is a useful tool for measuring the availability of equipment for example system verification 73% of 33 responded to a very large or a large extent. A majority o f the respondents genuinely see an advantage with the use of simulation, which i s an important result from the study. The cost reduction aspect of the productio n is also an advantage of DES. On the question eight answered to a very large ex tent and 23 to a large extent of total 39 replies. The question demonstrates tha t the results of a simulation model are indeed used in the real world. Finally, in the question of DES is used for staffing it is indicated that it is not so co mmonly used as for other functions asked for. The staffing issue requires good k nowledge about time measurement of manual labor. The option, however, to include manual work in a simulation model is in many programs extensive and must be a v aluable option to evaluate work intensive parts of production lines and their im provement. To conclude, it could be mentioned that DES is a tool with potential. The use is increasing and 12 of 80 companies investigated in Sweden 2001 are using it, an increase compared to previous stud-ies. Of those 12 companies, four are using t he tool to a large extent. The main advantage according to the survey beside the visualization part is that the knowledge about a system is investigated and doc umented.
文摘The Riyadh metro project is one of the current megaprojects that aim to improve the transit systems in Saudi Arabia.It consists of several metro lines with a total length of 176 km and 85 stations.The viaducts are considered as one of the main construction elements in the metro lines.Four methods for viaducts construction have been used in the Riyadh metro project:precast beam,full span launching method,cast on-site,and segment method(precast segment method and BCM(balanced cantilever method)).The viaducts work consumes a large portion of a project’s time and cost.Furthermore,the competitive nature of the construction industry increases the need to improve the efficiency of construction performance.Accordingly,this paper takes the initial steps toward increasing the efficiency of viaduct construction methods through simulation.Simulation of construction processes provides a systematic tool that can be used for determining the resources,time,and cost of these processes.The simulation processes should focus on the main activities affecting this element’s execution for viaducts construction,such as segment storage,handling,transporting,and installation.This study highlights the viaducts construction methods and develops general discrete-event simulation models for the most commonly used viaducts construction methods in the Riyadh metro using AnyLogic simulation software.The simulation models visualize and capture the interaction between the different activities and resources in a viaduct construction.Consequently,the construction drawbacks can be identified.Furthermore,the simulation model can be manipulated by adding assumptions to develop more efficient construction methods in terms of time and cost in such projects.
基金the Key Grant Project of Ministry of Education of the People’s Republic of China through Project,China(No.113027A)the Fundamental Research Funds for the Central Universities,China
文摘The goal of this paper is to provide an approach to investigate the variation of fiber quantity in a certain cross-section of the drafting zone. This model with discrete-event simulation( DES)method was presented to simulate the dynamic drafting process. This model described the behavior of individual fibers,which was divided into four phases and simulated by corresponding modules. Three sets of processing conditions in industry were simulated and demonstrated the applications of this model. The comparison between experiments and simulation results could also validate this model. This model could be used to simulate various drafting process with appropriate drafting settings.
文摘Object-oriented world-view provides a natural and powerful paradignl for expressing system elements and their dynamic behaviour for discrete-event simulation. Simulation gives the critical ability to study the dynamic behaviour of the models that are defined with object-voriented means. This paper first examines the ways of applying the object-oriented world-view to three major discrete simulation modelling approaches, then considers the process and merits of object-oriented simulation modelling.
基金National Key Research and Development Program of China(2022YFB4600902)Shandong Provincial Science Foundation for Outstanding Young Scholars(ZR2024YQ020)。
文摘Wire arc additive manufacturing(WAAM)has emerged as a promising approach for fabricating large-scale components.However,conventional WAAM still faces challenges in optimizing microstructural evolution,minimizing additive-induced defects,and alleviating residual stress and deformation,all of which are critical for enhancing the mechanical performance of the manufactured parts.Integrating interlayer friction stir processing(FSP)into WAAM significantly enhances the quality of deposited materials.However,numerical simulation research focusing on elucidating the associated thermomechanical coupling mechanisms remains insufficient.A comprehensive numerical model was developed to simulate the thermomechanical coupling behavior in friction stir-assisted WAAM.The influence of post-deposition FSP on the coupled thermomechanical response of the WAAM process was analyzed quantitatively.Moreover,the residual stress distribution and deformation behavior under both single-layer and multilayer deposition conditions were investigated.Thermal analysis of different deposition layers in WAAM and friction stir-assisted WAAM was conducted.Results show that subsequent layer deposition induces partial remelting of the previously solidified layer,whereas FSP does not cause such remelting.Furthermore,thermal stress and deformation analysis confirm that interlayer FSP effectively mitigates residual stresses and distortion in WAAM components,thereby improving their structural integrity and mechanical properties.
基金supported by the National Natural Science Foundation of China(Grant Nos.22193032 and 32401033)the Research Fund of Wenzhou Institute,Chinese Academy of Sciences(Grant Nos.WIUCASQD2020009,WIUCASQD2023005,XSZD2024004,2021HZSY0061,and WIUCASICTP2022)。
文摘The F_(1)-ATPase and V_(1)-ATPase are rotary biomotors.Alignment of their amino acid sequences,which originate from bovine heart mitochondria(1BMF)and Enterococcus hirae(3VR6),respectively,demonstrates that the segment forming the ATP catalytic pocket is highly conserved.Single-molecule experiments,however,have revealed subtle differences in efficiency between the F_(1) and V_(1) motors.Here,we perform both atomistic and coarse-grained molecular dynamics simulations to investigate the mechanochemical coupling and coordination in F_(1) and V_(1) ATPase.Our results show that the correlation between conformational changes in F_(1) is stronger than that in V_(1),indicating that the mechanochemical coupling in F_(1) is tighter than in V_(1).Moreover,the unidirectional rotation of F_(1) is more processive than that of V_(1),which accounts for the higher efficiency observed in F_(1) and explains the occasional backward steps detected in single-molecule experiments on V_(1).
基金supported by the Advanced Materials-National Science and Technology Major Project(Grant No.2025ZD0618401)the National Natural Science Foundation of China(Grant No.12504285)+1 种基金the Natural Science Foundation of Jiangsu Province(Grant No.BK20250472)NFSG grant from BITS-Pilani,Dubai campus。
文摘The rapid advancement of machine learning based tight-binding Hamiltonian(MLTB)methods has opened new avenues for efficient and accurate electronic structure simulations,particularly in large-scale systems and long-time scenarios.This review begins with a concise overview of traditional tight-binding(TB)models,including both(semi-)empirical and first-principles approaches,establishing the foundation for understanding MLTB developments.We then present a systematic classification of existing MLTB methodologies,grouped into two major categories:direct prediction of TB Hamiltonian elements and inference of empirical parameters.A comparative analysis with other ML-based electronic structure models is also provided,highlighting the advancement of MLTB approaches.Finally,we explore the emerging MLTB application ecosystem,highlighting how the integration of MLTB models with a diverse suite of post-processing tools from linear-scaling solvers to quantum transport frameworks and molecular dynamics interfaces is essential for tackling complex scientific problems across different domains.The continued advancement of this integrated paradigm promises to accelerate materials discovery and open new frontiers in the predictive simulation of complex quantum phenomena.
基金financially supported by the National Natural Science Foundation of China(Nos.52173020 and 52573023)。
文摘Vitrimers belong to a class of polymeric materials capable of bond exchange reactions,showing great promise for environmental protection and sustainable development.However,studies on the coupling mechanism between the bond exchange kinetics and segmental dynamics near the glass transition temperature(T_(g))remain scarce.Herein,we employed molecular dynamics simulations to investigate the dynamic heterogeneity of the segment motion and bond exchange in vitrimers.The simulation results revealed that the bond exchange energy barrier exerts a much stronger influence on the bond exchange kinetics than on the segmental dynamics.At lower temperatures,slower segmental relaxation further constraind the bond exchange rate.Additionally,increasing the bond exchange energy barrier markedly enhanced the dynamic heterogeneity of segment motion.A close correlation was observed between heterogeneity and bond exchange.This study elucidated the coupling mechanism between bond exchange and segmental dynamics at the molecular scale,thereby providing a theoretical basis for designing vitrimer materials with tunable dynamic properties.
文摘In federated learning,backdoor attacks have become an important research topic with their wide application in processing sensitive datasets.Since federated learning detects or modifies local models through defense mechanisms during aggregation,it is difficult to conduct effective backdoor attacks.In addition,existing backdoor attack methods are faced with challenges,such as low backdoor accuracy,poor ability to evade anomaly detection,and unstable model training.To address these challenges,a method called adaptive simulation backdoor attack(ASBA)is proposed.Specifically,ASBA improves the stability of model training by manipulating the local training process and using an adaptive mechanism,the ability of the malicious model to evade anomaly detection by combing large simulation training and clipping,and the backdoor accuracy by introducing a stimulus model to amplify the impact of the backdoor in the global model.Extensive comparative experiments under five advanced defense scenarios show that ASBA can effectively evade anomaly detection and achieve high backdoor accuracy in the global model.Furthermore,it exhibits excellent stability and effectiveness after multiple rounds of attacks,outperforming state-of-the-art backdoor attack methods.
基金financially supported by the National Natural Science Foundation of China(Nos.52303298 and 52233002)。
文摘UHMWPE fibers exhibit impressive modulus and strength,but they have not reached their theoretical limits.Researchers focus on molecular weight,orientation,and crystallinity of UHMWPE,yet their contributions to mechanical properties are unclear.Molecular dynamics simulations are valuable but often limited by computational constraints.Our aim is to simulate higher molecular weights to better represent real UHMWPE fibers.We used Packmol and Polyply methodologies to construct PE systems,with Polyply reproducing more reasonable properties of UHMWPE fibers.Additionally,tensile simulations showed that orientation and crystallinity greatly impact Young's modulus more than molecular weight.Energy decomposition indicated that higher molecular weights lead to covalent bonds that can withstand more energy during stretching,thus increasing breaking strength.Combining simulations with machine learning,we found that orientation has the most significant impact on Young's modulus,contributing 60%,and molecular weight plays the most crucial role in determining the breaking strength,accounting for 65%.This study provides a theoretical basis and guidelines for enhancing UHMWPE's modulus and strength.
基金funded by Humanities and Social Sciences of Ministry of Education Planning Fund of China,grant number 21YJA790009National Natural Science Foundation of China,grant number 72140001.
文摘With the rapid proliferation of electric vehicles,their charging loads pose new challenges to power grid stability and operational efficiency.To address this,this study employs a Monte Carlo simulation model to analyze the charging load characteristics of six battery electric vehicle categories in Hebei Province,leveraging multi-source probabilistic distribution data under typical operational scenarios.The findings reveal that electric vehicle charging loads are primarily concentrated during midday and nighttime periods,with significant load fluctuations exerting substantial pressure on the grid.In response,this paper proposes strategic interventions including optimized charging infrastructure planning,time-of-use electricity pricing mechanisms,and smart charging technologies to balance grid loads.The results provide a theoretical foundation for electric vehicle load forecasting,smart grid dispatching,and vehicle-grid integration,thereby enhancing grid operational efficiency and sustainability.
基金supported by the 2024 Research Fund of University of Ulsan.
文摘In recent years,three-dimensional reconstruction technologies that employ multiple cameras have continued to evolve significantly,enabling remote collaboration among users in extended Reality(XR)environments.In addition,methods for deploying multiple cameras for motion capture of users(e.g.,performers)are widely used in computer graphics.As the need to minimize and optimize the number of cameras grows to reduce costs,various technologies and research approaches focused on Optimal Camera Placement(OCP)are continually being proposed.However,as most existing studies assume homogeneous camera setups,there is a growing demand for studies on heterogeneous camera setups.For instance,technical demands keep emerging in scenarios with minimal camera configurations,especially regarding cost factors,the physical placement of cameras given the spatial structure,and image capture strategies for heterogeneous cameras,such as high-resolution RGB cameras and depth cameras.In this study,we propose a pre-visualization and simulation method for the optimal placement of heterogeneous cameras in XR environments,accounting for both the specifications of heterogeneous cameras(e.g.,field of view)and the physical configuration(e.g.,wall configuration)in real-world spaces.The proposed method performs a visibility analysis of cameras by considering each camera’s field-of-view volume,resolution,and unique characteristics,along with physicalspace constraints.This approach enables the optimal position and rotation of each camera to be recommended,along with the minimum number of cameras required.In the results of our study conducted in heterogeneous camera combinations,the proposed method achieved 81.7%~82.7%coverage of the target visual information using only 2~3 cameras.In contrast,single(or homogeneous)-typed cameras were required to use 11 cameras for 81.6%coverage.Accordingly,we found that camera deployment resources can be reduced with the proposed approaches.
文摘Because of the developed surface of the Triply PeriodicMinimumSurface(TPMS)structures,polylactide(PLA)products with a TPMS structure are thought to be promising bio soluble implants with the potential for targeted drug delivery.For implants,mechanical properties are key performance characteristics,so understanding the deformation and failure mechanisms is essential for selecting the appropriate implant structure.The deformation and fracture processes in PLA samples with different interior architectures have been studied through computer simulation and experimental research.Two TPMS topologies,the Schwarz Diamond and Gyroid architectures,were used for the sample construction by 3D printing.ANSYS software was utilized to simulate compressive deformation.It was found that under the same load,the vonMises stresses in the Gyroid structure are higher than those in the Schwartz Diamond structure,which was associated with the different orientations of the cells in the studied structures in relation to the direction of the loading axis.The deformation process occurs in the local regions of the studied TPMS structures.Maximum von Mises stresses were observed in the vertical parts of the structures oriented along the load direction.It was found that,unlike the Gyroid,the Schwartz Diamond structure contains a frame that forms unique stiffening ribs,which ensures the redistribution of the load under the vertical loading direction.An analysis of the mechanical characteristics of PLA samples with the Schwartz Diamond and Gyroid structures produced by the Fused Deposition Modeling(FDM)method was correlated with computer simulation.The Schwarz Diamond-type structure was shown to have a higher absorption energy than the Gyroid one.A study of the fracture in PLA samples with various cell sizes revealed a particular feature related to the samples’periodic surface topology and the 3D printing process.Scanning electron microscopic(SEM)studies of the samples deformed by compression showed thatwith an increase in the density of the samples,the failure mechanism changes from ductile to quasi-brittle due to the complex participation of both cell deformation and fiber deformation.
基金financial support from the National Key Research and Development Program of China(No.2023YFC2907904)the National Natural Science Foundation of China(Nos.52374364,52104355,52074363)+1 种基金National Sustainable Development Agenda Innovation Demonstration Zones:Provincial Special“Open Competition”Project in Chenzhou,China(No.2022sfq57)Postdoctoral Innovation Talent Support Program,China(No.BX20230438)。
文摘The effect of temperature on molten zone length was investigated through simulation to optimize the control of molten zone length during the experimental process. The temperature gradient distribution within the molten zone during zone refining was simulated using COMSOL Multiphysics software and experimentally validated. The simulated molten zone length showed good agreement with the actual measured length. The experimental study of tellurium purification by zone refining was conducted under the following conditions: three passes of zone refining, a hydrogen flow rate of 0.5 L/min, and molten zone movement speeds of 0.5 and 1.0 mm/min. The results demonstrated that the removal efficiencies of impurities such as Ca and Cu exceeded 95%, while the removal efficiency of phosphorus (P) reached over 70%. And the purity of tellurium reached 6N.
文摘Ice crystal icing is an important cause of accidents in aircraft engines.Ice formation in aircraft engines can cause internal blades to freeze,affecting the quality of the air flow field and blocking the flow path.On the other hand,the entry of ice crystal particles into the combustion chamber can cause a decrease in temperature or even flameout,leading to engine surge or shutdown.Therefore,it is necessary to conduct multiphase flow tests on ice crystals for aircraft components such as aircraft engines.Conducting ice crystal multiphase flow tests on aircraft is an effective research method,but it requires the construction of an ice crystal multiphase flow test platform that meets relevant technical requirements.The paper focuses on the relevant experimental requirements and combines wind tunnel test structures to conduct multiphase flow numerical simulations on various forms of jet pipelines,obtaining particle motion distribution results.After comparison,the optimal form of jet structure is obtained,providing the best selection scheme for the design of relevant wind tunnel structures.
基金financially supported by the National Natural Science Foundation of China(52130109)。
文摘Centrifugal casting of ductile iron pipe is a high-temperature,semi-continuous production process.However,conducting laboratory research on the solidification process of centrifugal casting of ductile iron pipe presents significant challenges.In this study,a novel research method was introduced for investigating the solidification process of ductile iron pipe,namely thermal simulation of ductile iron pipe.Comparative research was conducted on the microstructure and properties of the thermal simulation sample and the ductile iron pipe.The findings indicate that the thermal simulation sample and ductile iron pipe exhibit good heat transfer similarity and microstructure similarity.The difference of cooling rate between thermal simulation sample and ductile pipe is less than 0.24℃·s^(-1),and the difference of microstructure content of free cementite,ferrite,and pearlite is less than 5%.The tensile strength of annealed ductile iron pipe is 466 MPa,with an elongation of 16.1%and a Brinell hardness of 156.5 HBW.In comparison,the tensile strength of annealed thermal simulation sample is 482.0 MPa,with an elongation of 15.5%and a Brinell hardness of 159.0 HBW.These results suggest that the thermal simulation experimental research method is both scientific and feasible,offering an objective,reliable,and cost-effective approach to laboratory research on ductile iron pipe.
