Microbially induced calcite precipitation(MICP)and Enzyme induced calcite precipitation(EICP)techniques were implemented to reinforce the large-scale calcareous sand in this study.Then a coupled numerical model to pre...Microbially induced calcite precipitation(MICP)and Enzyme induced calcite precipitation(EICP)techniques were implemented to reinforce the large-scale calcareous sand in this study.Then a coupled numerical model to predict the biochemical reactions and hydraulic characteristics of MICP and EICP reactions was proposed and verified by physical experiments.Results showed that:This model could describe the variations of bacteria,calcium,calcite,permeability over time reasonably.It is necessary to consider the influence of the calculation domain scale when simulating the convection-diffusionreaction in the multi-process of MICP and EICP reactions.The numerical and experimental values of calcite content are 0.841 g/cm^(3) and 0.861 g/cm^(3) for MICP-reinforced sand,0.263 g/cm^(3) and 0.227 g/cm^(3) for EICP-reinforced sand after 192 h of reaction.The reaction rate k_(rea) is an important parameter to control the calcite content.Accordingly,the permeability coefficient of MICP and EICP reinforced calcareous sand decreases by 32%and 18%.Due to the influence of substance transportation and calcite precipitation,the calcite shows a trend of decreasing firstly and then increasing with the enhancing of the initial permeability coefficient in biochemical reactions.The optimal injecting ratio q11:q12 in this study is 100:300 mL/min.The process for the application of MICP and EICP coupled numerical model is also recommended,which provides reference for engineering projects in ground improvement.展开更多
In the aerospace industry,integrated aluminium alloy plates and stiffened panels with high accuracy and performance attract significant interest.To manufacture these panels as integrity with high accuracy,multiple pro...In the aerospace industry,integrated aluminium alloy plates and stiffened panels with high accuracy and performance attract significant interest.To manufacture these panels as integrity with high accuracy,multiple processes need to be utilised,such as machining,welding and forming.During the whole manufacturing chain,residual stresses can be generated and redistributed in the components among different processes.The residual stress would significantly affect the shapes and properties of the final products.Currently,these great effects are not well considered in the design and manufacturing processes.This paper aims to draw a general understanding of the residual stress generated in the pre-manufacturing processes and its effects on subsequent manufacturing processes.The mechanisms and distributions of residual stresses generated in typical premanufacturing processes of structural panels,including machining,welding and additive manufacturing(AM),are firstly summarised.The detailed effects of generated residual stresses on distortion and application properties in subsequent manufacturing processes are then concluded.In addition,current methods developed for the investigation of residual stress effect in multi-processes manufacturing are critically reviewed,including experimental,analytical,finite element(FE)and machine learning methods.Furthermore,the future development trend of methods for residual stress consideration and control in the design of manufacturing processes is summarised,providing comprehensive guidance to achieve the high accurate manufacturing of aluminium alloy structural components.展开更多
The quantitative evaluation of multi-process collaborative operation is of great significance for the improvement of production planning and scheduling in steelmaking–continuous casting sections(SCCSs). However, this...The quantitative evaluation of multi-process collaborative operation is of great significance for the improvement of production planning and scheduling in steelmaking–continuous casting sections(SCCSs). However, this evaluation is difficult since it relies on an in-depth understanding of the operating mechanism of SCCSs, and few existing methods can be used to conduct the evaluation, due to the lack of full-scale consideration of the multiple factors related to the production operation. In this study, three quantitative models were developed, and the multiprocess collaborative operation level was evaluated through the laminar-flow operation degree, the process matching degree, and the scheduling strategy availability degree. Based on the evaluation models for the laminar-flow operation and process matching levels, this study investigated the production status of two steelmaking plants, plants A and B, based on actual production data. The average laminar-flow operation(process matching) degrees of SCCSs were obtained as 0.638(0.610) and 1.000(0.759) for plants A and B, respectively, for the period of April to July 2019. Then, a scheduling strategy based on the optimization of the furnace-caster coordinating mode was suggested for plant A. Simulation experiments showed higher availability than the greedy-based and manual strategies. After the proposed scheduling strategy was applied,the average process matching degree of the SCCS of plant A increased by 4.6% for the period of September to November 2019. The multi-process collaborative operation level was improved with fewer adjustments and interruptions in casting.展开更多
On the basis of Space-Wise Least Square method, three numerical methods including Cholesky de- composition, pre-conditioned conjugate gradient and Open Multi-Processing parallel algorithm are applied into the determin...On the basis of Space-Wise Least Square method, three numerical methods including Cholesky de- composition, pre-conditioned conjugate gradient and Open Multi-Processing parallel algorithm are applied into the determination of gravity field with satellite gravity gradiometry data. The results show that, Cholesky de- composition method has been unable to meet the requirements of computation efficiency when the computer hardware is limited. Pre-conditioned conjugate gradient method can improve the computation efficiency of huge matrix inversion, but it also brings a certain loss of precision. The application of Open Multi-Processing parallel algorithm could achieve a good compromise between accuracy and computation efficiency.展开更多
The agricultural waste biomass holds potential as a valuable resource,capable of being converted into high-grade solid fuel for energy production.Despite the ample availability of rice straw and palm oil empty fruit b...The agricultural waste biomass holds potential as a valuable resource,capable of being converted into high-grade solid fuel for energy production.Despite the ample availability of rice straw and palm oil empty fruit bunch stock,challenges persist with biomass feedstock,such as low calorific values and high slagging-fouling potency.The wet torrefaction process,known as hydrothermal torrefaction,enhances agricultural waste biomass into solid fuel comparable to lignite and sub-bituminous coal.The study investigates the slagging-fouling potential of raw agriculture biomass waste and wet torrefaction-treated variants,evaluating sample characteristics through proximate,ultimate,and calorific value analyses.This study also investigates the potential of the wet torrefaction process as a pre-treatment in multi-process conversion.The moisture content of the wet torrefaction biomass decreased slightly,and the calorific value of the wet torrefaction biomass samples was higher than that of the raw biomass.The result of rice straw wet torrefaction at 240℃was a gross calorific value of 16.29 MJ/kg,equivalent to lignite A,with slagging potential decreased from 0.021(low)to 0.011(low),and the fouling potential from 0.921(medium)to 0.322(low).The result of palm oil empty fruit bunches,wet torrefaction at 240℃achieved the highest gross calorific value of 20.38 MJ/kg,equivalent to sub-bituminous C coal,with slagging potential reduced from 0.076(low)to 0.031(low)and fouling potential reduced from 74.84(high)to 20.27(medium).Wet torrefaction shows potential as a pre-treatment for multi-process conversion.Future studies should consider sequential torrefaction(wet and dry methods)that could leverage the advantages of each,reducing slagging and fouling potential while increasing the calorific value.展开更多
1 Introduction The explanation of the gain anomaly of the stimulated Raman scattering (SRS) in nonself-focusing medium has been one of the perplexing problems for all the researchers in quantum electronics, especially...1 Introduction The explanation of the gain anomaly of the stimulated Raman scattering (SRS) in nonself-focusing medium has been one of the perplexing problems for all the researchers in quantum electronics, especially the explanation of the Grun’s experimental result.展开更多
Unikernel,specializing a minimalistic libOS with an application,is an attractive design for cloud computing.However,the Achilles’heel of unikernel is the lack of multi-process support,which makes it less flexible and...Unikernel,specializing a minimalistic libOS with an application,is an attractive design for cloud computing.However,the Achilles’heel of unikernel is the lack of multi-process support,which makes it less flexible and applicable.Many applications rely on the process abstraction to isolate different components.For example,Apache with the multi-processing module isolates a request handler in a process to guarantee security.Prior art tackles the problem by simulating multi-process with multiple unikernels,which is incompatible with existing cloud providers and also introduces high overhead.This paper proposes Iso-UniK,a new unikernel design enabling multi-task applications with the support of both functionality and isolation.Iso-UniK leverages a recent hardware feature,named Intel Memory Protection Key(Intel MPK),to provide lightweight and efficient isolation for multi-process in unikernel.Our design has three benefits compared with previous approaches.First,Iso-UniK does not need hypervisor support and is thus compatible with existing cloud computing platforms;second,Iso-UniK promises fast system calls with only 45 cycles;last,a process can be isolated with a flexible configuration.We have implemented a prototype based on OSv,a unikernel system supporting unmodified applications.Iso-UniK can achieve fast fork operation with only 66μs for multi-process applications.Our evaluation shows that the isolation and multi-process support in Iso-UniK will not damage the applications’performance.展开更多
Unikernel,specializing a minimalistic libOS with an application,is an attractive design for cloud computing.However,the Achilles’heel of unikernel is the lack of multi-process support,which makes it less flexible and...Unikernel,specializing a minimalistic libOS with an application,is an attractive design for cloud computing.However,the Achilles’heel of unikernel is the lack of multi-process support,which makes it less flexible and applicable.Many applications rely on the process abstraction to isolate different components.For example,Apache with the multi-processing module isolates a request handler in a process to guarantee security.Prior art tackles the problem by simulating multi-process with multiple unikernels,which is incompatible with existing cloud providers and also introduces high overhead.This paper proposes Iso-UniK,a new unikernel design enabling multi-task applications with the support of both functionality and isolation.Iso-UniK leverages a recent hardware feature,named Intel Memory Protection Key(Intel MPK),to provide lightweight and efficient isolation for multi-process in unikernel.Our design has three benefits compared with previous approaches.First,Iso-UniK does not need hypervisor support and is thus compatible with existing cloud computing platforms;second,Iso-UniK promises fast system calls with only 45 cycles;last,a process can be isolated with a flexible configuration.We have implemented a prototype based on OSv,a unikernel system supporting unmodified applications.Iso-UniK can achieve fast fork operation with only 66μs for multi-process applications.Our evaluation shows that the isolation and multi-process support in Iso-UniK will not damage the applications’performance.展开更多
Realising adaptive traffic signal control(ATSC)through reinforcement learning(RL)is an important means to easetraffic congestion.This paper finds the computing power of the central processing unit(CPU)cannot fully use...Realising adaptive traffic signal control(ATSC)through reinforcement learning(RL)is an important means to easetraffic congestion.This paper finds the computing power of the central processing unit(CPU)cannot fully usedwhen Simulation of Urban MObility(SUMO)is used as an environment simulator for RL.We propose a multi-process framework under value-basedRL.First,we propose a shared memory mechanism to improve exploration efficiency.Second,we use the weight sharing mechanism to solve the problem of asynchronous multi-process agents.We also explained the reason shared memory in ATSC does not lead to early local optima of the agent.Wehave verified in experiments the sampling efficiency of the 10-process method is 8.259 times that of the single process.The sampling efficiency of the 20-process method is 13.409 times that of the single process.Moreover,the agent can also converge to the optimal solution.展开更多
基金supports from the National Key R&D Program of China(Grant No.2023YFB4203301)National Natural Science Foundation of China(Grant No.52238008)Postdoctoral Fellowship Program of CPSF(Grant No.GZC20241516).
文摘Microbially induced calcite precipitation(MICP)and Enzyme induced calcite precipitation(EICP)techniques were implemented to reinforce the large-scale calcareous sand in this study.Then a coupled numerical model to predict the biochemical reactions and hydraulic characteristics of MICP and EICP reactions was proposed and verified by physical experiments.Results showed that:This model could describe the variations of bacteria,calcium,calcite,permeability over time reasonably.It is necessary to consider the influence of the calculation domain scale when simulating the convection-diffusionreaction in the multi-process of MICP and EICP reactions.The numerical and experimental values of calcite content are 0.841 g/cm^(3) and 0.861 g/cm^(3) for MICP-reinforced sand,0.263 g/cm^(3) and 0.227 g/cm^(3) for EICP-reinforced sand after 192 h of reaction.The reaction rate k_(rea) is an important parameter to control the calcite content.Accordingly,the permeability coefficient of MICP and EICP reinforced calcareous sand decreases by 32%and 18%.Due to the influence of substance transportation and calcite precipitation,the calcite shows a trend of decreasing firstly and then increasing with the enhancing of the initial permeability coefficient in biochemical reactions.The optimal injecting ratio q11:q12 in this study is 100:300 mL/min.The process for the application of MICP and EICP coupled numerical model is also recommended,which provides reference for engineering projects in ground improvement.
基金co-supported by the National Natural Science Foundation of China(No.52005020)Guangdong Basic and Applied Basic Research Foundation(No.2019A1515110851).
文摘In the aerospace industry,integrated aluminium alloy plates and stiffened panels with high accuracy and performance attract significant interest.To manufacture these panels as integrity with high accuracy,multiple processes need to be utilised,such as machining,welding and forming.During the whole manufacturing chain,residual stresses can be generated and redistributed in the components among different processes.The residual stress would significantly affect the shapes and properties of the final products.Currently,these great effects are not well considered in the design and manufacturing processes.This paper aims to draw a general understanding of the residual stress generated in the pre-manufacturing processes and its effects on subsequent manufacturing processes.The mechanisms and distributions of residual stresses generated in typical premanufacturing processes of structural panels,including machining,welding and additive manufacturing(AM),are firstly summarised.The detailed effects of generated residual stresses on distortion and application properties in subsequent manufacturing processes are then concluded.In addition,current methods developed for the investigation of residual stress effect in multi-processes manufacturing are critically reviewed,including experimental,analytical,finite element(FE)and machine learning methods.Furthermore,the future development trend of methods for residual stress consideration and control in the design of manufacturing processes is summarised,providing comprehensive guidance to achieve the high accurate manufacturing of aluminium alloy structural components.
基金financially supported by the National Natural Science Foundation of China (Nos.50874014 and 51974023)the Fundamental Research Funds for Central Universities (No.FRF-BR-17-029A)。
文摘The quantitative evaluation of multi-process collaborative operation is of great significance for the improvement of production planning and scheduling in steelmaking–continuous casting sections(SCCSs). However, this evaluation is difficult since it relies on an in-depth understanding of the operating mechanism of SCCSs, and few existing methods can be used to conduct the evaluation, due to the lack of full-scale consideration of the multiple factors related to the production operation. In this study, three quantitative models were developed, and the multiprocess collaborative operation level was evaluated through the laminar-flow operation degree, the process matching degree, and the scheduling strategy availability degree. Based on the evaluation models for the laminar-flow operation and process matching levels, this study investigated the production status of two steelmaking plants, plants A and B, based on actual production data. The average laminar-flow operation(process matching) degrees of SCCSs were obtained as 0.638(0.610) and 1.000(0.759) for plants A and B, respectively, for the period of April to July 2019. Then, a scheduling strategy based on the optimization of the furnace-caster coordinating mode was suggested for plant A. Simulation experiments showed higher availability than the greedy-based and manual strategies. After the proposed scheduling strategy was applied,the average process matching degree of the SCCS of plant A increased by 4.6% for the period of September to November 2019. The multi-process collaborative operation level was improved with fewer adjustments and interruptions in casting.
基金supproted by the National Natural Science Foundation of China(40874012,40904003,40974016,41004007)
文摘On the basis of Space-Wise Least Square method, three numerical methods including Cholesky de- composition, pre-conditioned conjugate gradient and Open Multi-Processing parallel algorithm are applied into the determination of gravity field with satellite gravity gradiometry data. The results show that, Cholesky de- composition method has been unable to meet the requirements of computation efficiency when the computer hardware is limited. Pre-conditioned conjugate gradient method can improve the computation efficiency of huge matrix inversion, but it also brings a certain loss of precision. The application of Open Multi-Processing parallel algorithm could achieve a good compromise between accuracy and computation efficiency.
基金supported by“Research,Community Services,and Innovation Program(PPMI)FTMD ITB 2024”and“The Indonesian Endowment Funds for Education(LPDP)”.The experiment was conducted in the Thermodynamics Laboratory at Pusat Rekayasa Industri of Institut Teknologi Bandung and the Testing Center for Mineral and Coal Indonesia(Tekmira).
文摘The agricultural waste biomass holds potential as a valuable resource,capable of being converted into high-grade solid fuel for energy production.Despite the ample availability of rice straw and palm oil empty fruit bunch stock,challenges persist with biomass feedstock,such as low calorific values and high slagging-fouling potency.The wet torrefaction process,known as hydrothermal torrefaction,enhances agricultural waste biomass into solid fuel comparable to lignite and sub-bituminous coal.The study investigates the slagging-fouling potential of raw agriculture biomass waste and wet torrefaction-treated variants,evaluating sample characteristics through proximate,ultimate,and calorific value analyses.This study also investigates the potential of the wet torrefaction process as a pre-treatment in multi-process conversion.The moisture content of the wet torrefaction biomass decreased slightly,and the calorific value of the wet torrefaction biomass samples was higher than that of the raw biomass.The result of rice straw wet torrefaction at 240℃was a gross calorific value of 16.29 MJ/kg,equivalent to lignite A,with slagging potential decreased from 0.021(low)to 0.011(low),and the fouling potential from 0.921(medium)to 0.322(low).The result of palm oil empty fruit bunches,wet torrefaction at 240℃achieved the highest gross calorific value of 20.38 MJ/kg,equivalent to sub-bituminous C coal,with slagging potential reduced from 0.076(low)to 0.031(low)and fouling potential reduced from 74.84(high)to 20.27(medium).Wet torrefaction shows potential as a pre-treatment for multi-process conversion.Future studies should consider sequential torrefaction(wet and dry methods)that could leverage the advantages of each,reducing slagging and fouling potential while increasing the calorific value.
文摘1 Introduction The explanation of the gain anomaly of the stimulated Raman scattering (SRS) in nonself-focusing medium has been one of the perplexing problems for all the researchers in quantum electronics, especially the explanation of the Grun’s experimental result.
基金Sponsored by Program of Shanghai Academic/Technology Research Leader(No.19XD1401700).
文摘Unikernel,specializing a minimalistic libOS with an application,is an attractive design for cloud computing.However,the Achilles’heel of unikernel is the lack of multi-process support,which makes it less flexible and applicable.Many applications rely on the process abstraction to isolate different components.For example,Apache with the multi-processing module isolates a request handler in a process to guarantee security.Prior art tackles the problem by simulating multi-process with multiple unikernels,which is incompatible with existing cloud providers and also introduces high overhead.This paper proposes Iso-UniK,a new unikernel design enabling multi-task applications with the support of both functionality and isolation.Iso-UniK leverages a recent hardware feature,named Intel Memory Protection Key(Intel MPK),to provide lightweight and efficient isolation for multi-process in unikernel.Our design has three benefits compared with previous approaches.First,Iso-UniK does not need hypervisor support and is thus compatible with existing cloud computing platforms;second,Iso-UniK promises fast system calls with only 45 cycles;last,a process can be isolated with a flexible configuration.We have implemented a prototype based on OSv,a unikernel system supporting unmodified applications.Iso-UniK can achieve fast fork operation with only 66μs for multi-process applications.Our evaluation shows that the isolation and multi-process support in Iso-UniK will not damage the applications’performance.
基金Sponsored by Program of Shanghai Academic/Technology Research Leader(No.19XD1401700).
文摘Unikernel,specializing a minimalistic libOS with an application,is an attractive design for cloud computing.However,the Achilles’heel of unikernel is the lack of multi-process support,which makes it less flexible and applicable.Many applications rely on the process abstraction to isolate different components.For example,Apache with the multi-processing module isolates a request handler in a process to guarantee security.Prior art tackles the problem by simulating multi-process with multiple unikernels,which is incompatible with existing cloud providers and also introduces high overhead.This paper proposes Iso-UniK,a new unikernel design enabling multi-task applications with the support of both functionality and isolation.Iso-UniK leverages a recent hardware feature,named Intel Memory Protection Key(Intel MPK),to provide lightweight and efficient isolation for multi-process in unikernel.Our design has three benefits compared with previous approaches.First,Iso-UniK does not need hypervisor support and is thus compatible with existing cloud computing platforms;second,Iso-UniK promises fast system calls with only 45 cycles;last,a process can be isolated with a flexible configuration.We have implemented a prototype based on OSv,a unikernel system supporting unmodified applications.Iso-UniK can achieve fast fork operation with only 66μs for multi-process applications.Our evaluation shows that the isolation and multi-process support in Iso-UniK will not damage the applications’performance.
基金Gansu Education Department:[Grant Number 2021CXZX-515]National Natural Science Foundation of China:[Grant Number 61763028].
文摘Realising adaptive traffic signal control(ATSC)through reinforcement learning(RL)is an important means to easetraffic congestion.This paper finds the computing power of the central processing unit(CPU)cannot fully usedwhen Simulation of Urban MObility(SUMO)is used as an environment simulator for RL.We propose a multi-process framework under value-basedRL.First,we propose a shared memory mechanism to improve exploration efficiency.Second,we use the weight sharing mechanism to solve the problem of asynchronous multi-process agents.We also explained the reason shared memory in ATSC does not lead to early local optima of the agent.Wehave verified in experiments the sampling efficiency of the 10-process method is 8.259 times that of the single process.The sampling efficiency of the 20-process method is 13.409 times that of the single process.Moreover,the agent can also converge to the optimal solution.
