Crystalline silicon(c-Si)solar cells,though dominating the photovoltaic market,are nearing their theoretical power conversion efficiencies(PCE)limit of 29.4%,necessitating the adoption of multi-junction technology to ...Crystalline silicon(c-Si)solar cells,though dominating the photovoltaic market,are nearing their theoretical power conversion efficiencies(PCE)limit of 29.4%,necessitating the adoption of multi-junction technology to achieve higher performance.Among these,perovskiteon-silicon-based multi-junction solar cells have emerged as a promising alternative,where the perovskite offering tunable bandgaps,superior optoelectronic properties,and cost-effective manufacturing.Recent announced double-junction solar cells(PSDJSCs)have achieved the PCE of 34.85%,surpassing all other double-junction technologies.Encouragingly,the rapid advancements in PSDJSCs have spurred increased research interest in perovskite/perovskite/silicon triple-junction solar cells(PSTJSCs)in 2024.This triple-junction solar cell configuration demonstrates immense potential due to their optimum balance between achieving a high PCE limit and managing device complexity.This review provides a comprehensive analysis of PSTJSCs,covering fundamental principles,and technological milestones.Current challenges,including current mismatch,open-circuit voltage deficits,phase segregation,and stability issues,and their corresponding strategies are also discussed,alongside future directions to achieve long-term stability and high PCE.This work aims to advance the understanding of the development in PSTJSCs,paving the way for their practical implementation.展开更多
The use of Minimum Quantity Lubrication(MQL)with bio-lubricants has been extensively studied in aerospace sustainable manufacturing.Enhanced MQL technologies have been proposed to reduce tool wear and improve workpiec...The use of Minimum Quantity Lubrication(MQL)with bio-lubricants has been extensively studied in aerospace sustainable manufacturing.Enhanced MQL technologies have been proposed to reduce tool wear and improve workpiece surface integrity by increasing lubricant activity.However,the relationship between enhancement behavior,physicochemical properties of biolubricants,and processability remains unclear,presenting challenges for MQL technologies,particularly with difficult-to-machine materials.To address this gap,this paper provides an in-depth mechanism analysis and a comprehensive quantitative evaluation of the machinability of enhanced MQL technologies,considering chemistry,molecular dynamics,fluid dynamics,tribology,and heat transfer.Firstly,the cooling and lubrication enhancement mechanisms of nano-lubricants were systematically summarized.focusing on molecular structure.physical properties,and preparation processes.Secondly,the atomization enhancement mechanism of Electrostatic Minimum Quantity Lubrication(EMQL)was analyzed.revealing a 49%reduction in PM2.5 concentration during the atomization process compared to conventional MQL.Thirdly,the transport and infiltration enhancement mechanisms of bio-lubricants in cutting and grinding zones were summarized,incorporating electromagnetic fields and ultrasound-assisted processes.Finally,for cutting and grinding applications involving difficult-to-machine materials in aerospace,the optimized machinability of enhanced MQL technologies was concluded,showing a 50.1%increase in lubricant heat transfer coefficient and a 31.6%decrease in grinding temperature compared to standard MQL.This paper aims to help scientists understand the effective mechanisms,formulate process specifications,and identify future development trends in this technology.展开更多
Microgrinding is widely used in clinical bone surgery,but saline spray cooling faces technical challenges such as low wettability at the microgrinding tool–bone interface,easy clogging of the microgrinding tools,and ...Microgrinding is widely used in clinical bone surgery,but saline spray cooling faces technical challenges such as low wettability at the microgrinding tool–bone interface,easy clogging of the microgrinding tools,and high grinding temperatures.These issues can lead to bone necrosis,irreversible thermal damage to nerves,or even surgical failure.Inspired by the water-trapping and directional transportation abilities of desert beetles,this study proposes a biomimetic desert beetle microgrinding tool.The flow-field distribution directly influences the convective heat transfer of the cooling medium in the grinding zone,which in turn affects the grinding temperature.To address this,a mathematical model of the two-phase flow field at the biomimetic microgrinding tool–bone interface is developed.The results indicate an average error of 14.74%between the calculated and experimentally obtained airflow field velocities.Next,a biomimetic desert beetle microgrinding tool is prepared.Experiments with physiological saline spray cooling were conducted on fresh bovine femur bone,which has mechanical properties similar to human bone.Results show that,compared with conventional microgrinding tools,the biomimetic tools reduced bone surface temperature by 21.7%,13.2%,5.8%,20.3%,and 25.8%at particle sizes of 150#,200#,240#,270#,and 300#,respectively.The surface morphology of the biomimetic microgrinding tools after grinding is observed and analyzed,revealing a maximum clogging area reduction of 23.0%,which is 6.1%,6.0%,10.0%,15.6%,and 9.5%less than that observed with conventional tools.Finally,this study unveils the dynamic mechanism of cooling medium transfer in the flow field at the biomimetic microgrinding tool–bone interface.This research provides theoretical guidance and technical support for clinical bone resection surgery.展开更多
The rapid advance of Connected-Automated Vehicles(CAVs)has led to the emergence of diverse delaysensitive and energy-constrained vehicular applications.Given the high dynamics of vehicular networks,unmanned aerial veh...The rapid advance of Connected-Automated Vehicles(CAVs)has led to the emergence of diverse delaysensitive and energy-constrained vehicular applications.Given the high dynamics of vehicular networks,unmanned aerial vehicles-assisted mobile edge computing(UAV-MEC)has gained attention in providing computing resources to vehicles and optimizing system costs.We model the computing offloading problem as a multi-objective optimization challenge aimed at minimizing both task processing delay and energy consumption.We propose a three-stage hybrid offloading scheme called Dynamic Vehicle Clustering Game-based Multi-objective Whale Optimization Algorithm(DVCG-MWOA)to address this problem.A novel dynamic clustering algorithm is designed based on vehiclemobility and task offloading efficiency requirements,where each UAV independently serves as the cluster head for a vehicle cluster and adjusts its position at the end of each timeslot in response to vehiclemovement.Within eachUAV-led cluster,cooperative game theory is applied to allocate computing resourceswhile respecting delay constraints,ensuring efficient resource utilization.To enhance offloading efficiency,we improve the multi-objective whale optimization algorithm(MOWOA),resulting in the MWOA.This enhanced algorithm determines the optimal allocation of pending tasks to different edge computing devices and the resource utilization ratio of each device,ultimately achieving a Pareto-optimal solution set for delay and energy consumption.Experimental results demonstrate that the proposed joint offloading scheme significantly reduces both delay and energy consumption compared to existing approaches,offering superior performance for vehicular networks.展开更多
With the continuous expansion of the data center network scale, changing network requirements, and increasing pressure on network bandwidth, the traditional network architecture can no longer meet people’s needs. The...With the continuous expansion of the data center network scale, changing network requirements, and increasing pressure on network bandwidth, the traditional network architecture can no longer meet people’s needs. The development of software defined networks has brought new opportunities and challenges to future networks. The data and control separation characteristics of SDN improve the performance of the entire network. Researchers have integrated SDN architecture into data centers to improve network resource utilization and performance. This paper first introduces the basic concepts of SDN and data center networks. Then it discusses SDN-based load balancing mechanisms for data centers from different perspectives. Finally, it summarizes and looks forward to the study on SDN-based load balancing mechanisms and its development trend.展开更多
Too high grinding force will lead to a large increase in specific grinding energy, resulting in high temperature in grinding zone, especially for the aerospace difficult cutting metal materials,seriously affecting the...Too high grinding force will lead to a large increase in specific grinding energy, resulting in high temperature in grinding zone, especially for the aerospace difficult cutting metal materials,seriously affecting the surface quality and accuracy. At present, the theoretical models of grinding force are mostly based on the assumption of uniform or simplified morphological characteristics of grains, which is inconsistent with the actual grains. Especially for non-engineering grinding wheel,most geometric characteristics of grains are ignored, resulting in the calculation accuracy that cannot guide practical production. Based on this, an improved grinding force model based on random grain geometric characteristics is proposed in this paper. Firstly, the surface topography model of CBN grinding wheel is established, and the effective grain determination mechanism in grinding zone is revealed. Based on the known grinding force model and mechanical behavior of interaction between grains and workpiece in different stages, the concept of grain effective action area is proposed. The variation mechanism of effective action area under the influence of grain geometric and spatial characteristics is deeply analyzed, and the calculation method under random combination of five influencing parameters is obtained. The numerical simulation is carried out to reveal the dynamic variation process of grinding force in grinding zone. In order to verify the theoretical model, the experiments of dry grinding Ti-6Al-4 V are designed. The experimental results show that under different machining parameters, the results of numerical calculation and experimental measurement are in good agreement, and the minimum error value is only 2.1 %, which indicates that the calculation accuracy of grinding force model meets the requirements and is feasible. This study will provide a theoretical basis for optimizing the wheel structure, effectively controlling the grinding force range, adjusting the grinding zone temperature and improving the workpiece machining quality in the industrial grinding process.展开更多
It is an inevitable trend of sustainable manufacturing to replace flood and dry machining with minimum quantity lubrication(MQL)technology.Nevertheless,for aeronautical difficult-tomachine materials,MQL couldn’t meet...It is an inevitable trend of sustainable manufacturing to replace flood and dry machining with minimum quantity lubrication(MQL)technology.Nevertheless,for aeronautical difficult-tomachine materials,MQL couldn’t meet the high demand of cooling and lubrication due to high heat generation during machining.Nano-biolubricants,especially non-toxic carbon group nano-enhancers(CGNs)are used,can solve this technical bottleneck.However,the machining mechanisms under lubrication of CGNs are unclear at complex interface between tool and workpiece,which characterized by high temperature,pressure,and speed,limited its application in factories and necessitates in-depth understanding.To fill this gap,this study concentrates on the comprehensive quantitative assessment of tribological characteristics based on force,tool wear,chip,and surface integrity in titanium alloy and nickel alloy machining and attempts to answer mechanisms systematically.First,to establish evaluation standard,the cutting mechanisms and performance improvement behavior covering antifriction,antiwear,tool failure,material removal,and surface formation of MQL were revealed.Second,the unique film formation and lubrication behaviors of CGNs in MQL turning,milling,and grinding are concluded.The influence law of molecular structure and micromorphology of CGNs was also answered and optimized options were recommended by considering diverse boundary conditions.Finally,in view of CGNs limitations in MQL,the future development direction is proposed,which needs to be improved in thermal stability of lubricant,activity of CGNs,controllable atomization and transportation methods,and intelligent formation of processing technology solutions.展开更多
基金supported by the National Natural Science Foundation of China under Grants 62404185the industry-academia joint laboratory collaboration between Hiking PV and Xiamen University(20243160C0010)J.Z.is supported by Nanqiang Outstanding Young Talents Program X2450215 of Xiamen University.
文摘Crystalline silicon(c-Si)solar cells,though dominating the photovoltaic market,are nearing their theoretical power conversion efficiencies(PCE)limit of 29.4%,necessitating the adoption of multi-junction technology to achieve higher performance.Among these,perovskiteon-silicon-based multi-junction solar cells have emerged as a promising alternative,where the perovskite offering tunable bandgaps,superior optoelectronic properties,and cost-effective manufacturing.Recent announced double-junction solar cells(PSDJSCs)have achieved the PCE of 34.85%,surpassing all other double-junction technologies.Encouragingly,the rapid advancements in PSDJSCs have spurred increased research interest in perovskite/perovskite/silicon triple-junction solar cells(PSTJSCs)in 2024.This triple-junction solar cell configuration demonstrates immense potential due to their optimum balance between achieving a high PCE limit and managing device complexity.This review provides a comprehensive analysis of PSTJSCs,covering fundamental principles,and technological milestones.Current challenges,including current mismatch,open-circuit voltage deficits,phase segregation,and stability issues,and their corresponding strategies are also discussed,alongside future directions to achieve long-term stability and high PCE.This work aims to advance the understanding of the development in PSTJSCs,paving the way for their practical implementation.
基金supported by the following organizations:the Special Fund of Taishan Scholars Project(No.tsqn202211179)the National Natural Science Foundation of China(No.52105457)+2 种基金Young Talent of Lifting engineering for Science and Technology in Shandong,China(No.SDAST2021qt12)the National Natural Science Foundation of China(No.52375447)China Postdoctoral Science Foundation Funded Project(No.2023M732826).
文摘The use of Minimum Quantity Lubrication(MQL)with bio-lubricants has been extensively studied in aerospace sustainable manufacturing.Enhanced MQL technologies have been proposed to reduce tool wear and improve workpiece surface integrity by increasing lubricant activity.However,the relationship between enhancement behavior,physicochemical properties of biolubricants,and processability remains unclear,presenting challenges for MQL technologies,particularly with difficult-to-machine materials.To address this gap,this paper provides an in-depth mechanism analysis and a comprehensive quantitative evaluation of the machinability of enhanced MQL technologies,considering chemistry,molecular dynamics,fluid dynamics,tribology,and heat transfer.Firstly,the cooling and lubrication enhancement mechanisms of nano-lubricants were systematically summarized.focusing on molecular structure.physical properties,and preparation processes.Secondly,the atomization enhancement mechanism of Electrostatic Minimum Quantity Lubrication(EMQL)was analyzed.revealing a 49%reduction in PM2.5 concentration during the atomization process compared to conventional MQL.Thirdly,the transport and infiltration enhancement mechanisms of bio-lubricants in cutting and grinding zones were summarized,incorporating electromagnetic fields and ultrasound-assisted processes.Finally,for cutting and grinding applications involving difficult-to-machine materials in aerospace,the optimized machinability of enhanced MQL technologies was concluded,showing a 50.1%increase in lubricant heat transfer coefficient and a 31.6%decrease in grinding temperature compared to standard MQL.This paper aims to help scientists understand the effective mechanisms,formulate process specifications,and identify future development trends in this technology.
基金Supported by National Natural Science Foundation of China(Grant Nos.52205481,52305477)Outstanding Youth Innovation Team in Universities of Shandong Province(Grant No.2023KJ114)+2 种基金Qingdao Science and Technology Planning Park Cultivation Plan(Grant No.23-1-5-yqpy-17-qy)Young Talent of Lifting engineering for Science and Technology in Shandong(Grant No.SDAST2024QTA043)Key Lab of Industrial Fluid Energy Conservation and Pollution Control(Ministry of Education)(Grant No.CK-2024-0033)。
文摘Microgrinding is widely used in clinical bone surgery,but saline spray cooling faces technical challenges such as low wettability at the microgrinding tool–bone interface,easy clogging of the microgrinding tools,and high grinding temperatures.These issues can lead to bone necrosis,irreversible thermal damage to nerves,or even surgical failure.Inspired by the water-trapping and directional transportation abilities of desert beetles,this study proposes a biomimetic desert beetle microgrinding tool.The flow-field distribution directly influences the convective heat transfer of the cooling medium in the grinding zone,which in turn affects the grinding temperature.To address this,a mathematical model of the two-phase flow field at the biomimetic microgrinding tool–bone interface is developed.The results indicate an average error of 14.74%between the calculated and experimentally obtained airflow field velocities.Next,a biomimetic desert beetle microgrinding tool is prepared.Experiments with physiological saline spray cooling were conducted on fresh bovine femur bone,which has mechanical properties similar to human bone.Results show that,compared with conventional microgrinding tools,the biomimetic tools reduced bone surface temperature by 21.7%,13.2%,5.8%,20.3%,and 25.8%at particle sizes of 150#,200#,240#,270#,and 300#,respectively.The surface morphology of the biomimetic microgrinding tools after grinding is observed and analyzed,revealing a maximum clogging area reduction of 23.0%,which is 6.1%,6.0%,10.0%,15.6%,and 9.5%less than that observed with conventional tools.Finally,this study unveils the dynamic mechanism of cooling medium transfer in the flow field at the biomimetic microgrinding tool–bone interface.This research provides theoretical guidance and technical support for clinical bone resection surgery.
基金funded by Shandong University of Technology Doctoral Program in Science and Technology,grant number 4041422007.
文摘The rapid advance of Connected-Automated Vehicles(CAVs)has led to the emergence of diverse delaysensitive and energy-constrained vehicular applications.Given the high dynamics of vehicular networks,unmanned aerial vehicles-assisted mobile edge computing(UAV-MEC)has gained attention in providing computing resources to vehicles and optimizing system costs.We model the computing offloading problem as a multi-objective optimization challenge aimed at minimizing both task processing delay and energy consumption.We propose a three-stage hybrid offloading scheme called Dynamic Vehicle Clustering Game-based Multi-objective Whale Optimization Algorithm(DVCG-MWOA)to address this problem.A novel dynamic clustering algorithm is designed based on vehiclemobility and task offloading efficiency requirements,where each UAV independently serves as the cluster head for a vehicle cluster and adjusts its position at the end of each timeslot in response to vehiclemovement.Within eachUAV-led cluster,cooperative game theory is applied to allocate computing resourceswhile respecting delay constraints,ensuring efficient resource utilization.To enhance offloading efficiency,we improve the multi-objective whale optimization algorithm(MOWOA),resulting in the MWOA.This enhanced algorithm determines the optimal allocation of pending tasks to different edge computing devices and the resource utilization ratio of each device,ultimately achieving a Pareto-optimal solution set for delay and energy consumption.Experimental results demonstrate that the proposed joint offloading scheme significantly reduces both delay and energy consumption compared to existing approaches,offering superior performance for vehicular networks.
文摘With the continuous expansion of the data center network scale, changing network requirements, and increasing pressure on network bandwidth, the traditional network architecture can no longer meet people’s needs. The development of software defined networks has brought new opportunities and challenges to future networks. The data and control separation characteristics of SDN improve the performance of the entire network. Researchers have integrated SDN architecture into data centers to improve network resource utilization and performance. This paper first introduces the basic concepts of SDN and data center networks. Then it discusses SDN-based load balancing mechanisms for data centers from different perspectives. Finally, it summarizes and looks forward to the study on SDN-based load balancing mechanisms and its development trend.
基金2021年国家外专项目“人工智能和未来教育前沿问题研究与教学改革探索”(编号:G2021111027L)2021英国社会经济研究委员会项目“From principles to practices:AI ethics in education”广东省教育科学规划课题“互联网+国际教育:高校学生自主性学习和新型能力培养的研究”(编号:2021GXJK375)。
基金2021年国家外专项目“人工智能和未来教育前沿问题研究与教学改革探索”(编号:G2021111027L)2021英国社会经济研究委员会项目“From principles to practices:AI ethics in education”广东省教育科学规划课题“互联网+国际教育:高校学生自主性学习和新型能力培养的研究”(编号:2021GXJK375)。
基金supported by the National Natural Science Foundation of China(Nos.51975305,51905289,52105264)the Key Project of Shandong Province,China(No.ZR2020KE027)+1 种基金the Major Research Project of Shandong Province,China(Nos.2019GGX104040 and 2019GSF108236)the Natural Science Foundation of Shandong Province,China(No.ZR2021QE116).
文摘Too high grinding force will lead to a large increase in specific grinding energy, resulting in high temperature in grinding zone, especially for the aerospace difficult cutting metal materials,seriously affecting the surface quality and accuracy. At present, the theoretical models of grinding force are mostly based on the assumption of uniform or simplified morphological characteristics of grains, which is inconsistent with the actual grains. Especially for non-engineering grinding wheel,most geometric characteristics of grains are ignored, resulting in the calculation accuracy that cannot guide practical production. Based on this, an improved grinding force model based on random grain geometric characteristics is proposed in this paper. Firstly, the surface topography model of CBN grinding wheel is established, and the effective grain determination mechanism in grinding zone is revealed. Based on the known grinding force model and mechanical behavior of interaction between grains and workpiece in different stages, the concept of grain effective action area is proposed. The variation mechanism of effective action area under the influence of grain geometric and spatial characteristics is deeply analyzed, and the calculation method under random combination of five influencing parameters is obtained. The numerical simulation is carried out to reveal the dynamic variation process of grinding force in grinding zone. In order to verify the theoretical model, the experiments of dry grinding Ti-6Al-4 V are designed. The experimental results show that under different machining parameters, the results of numerical calculation and experimental measurement are in good agreement, and the minimum error value is only 2.1 %, which indicates that the calculation accuracy of grinding force model meets the requirements and is feasible. This study will provide a theoretical basis for optimizing the wheel structure, effectively controlling the grinding force range, adjusting the grinding zone temperature and improving the workpiece machining quality in the industrial grinding process.
基金supported by the National Natural Science Foundation of China(Nos.51975305 and 51905289)the Major Research Project of Shandong Province(No.2019GGX104040)+2 种基金the Major Science and Technology Innovation Engineering Projects of Shandong Province(No.2019JZZY020111)the Natural Science Foundation of Shandong Province(Nos.ZR2020KE027 and ZR2020ME158)the Applied Basic Research Youth Project of Qingdao science and technology plan(No.19-6-2-63-cg)。
文摘It is an inevitable trend of sustainable manufacturing to replace flood and dry machining with minimum quantity lubrication(MQL)technology.Nevertheless,for aeronautical difficult-tomachine materials,MQL couldn’t meet the high demand of cooling and lubrication due to high heat generation during machining.Nano-biolubricants,especially non-toxic carbon group nano-enhancers(CGNs)are used,can solve this technical bottleneck.However,the machining mechanisms under lubrication of CGNs are unclear at complex interface between tool and workpiece,which characterized by high temperature,pressure,and speed,limited its application in factories and necessitates in-depth understanding.To fill this gap,this study concentrates on the comprehensive quantitative assessment of tribological characteristics based on force,tool wear,chip,and surface integrity in titanium alloy and nickel alloy machining and attempts to answer mechanisms systematically.First,to establish evaluation standard,the cutting mechanisms and performance improvement behavior covering antifriction,antiwear,tool failure,material removal,and surface formation of MQL were revealed.Second,the unique film formation and lubrication behaviors of CGNs in MQL turning,milling,and grinding are concluded.The influence law of molecular structure and micromorphology of CGNs was also answered and optimized options were recommended by considering diverse boundary conditions.Finally,in view of CGNs limitations in MQL,the future development direction is proposed,which needs to be improved in thermal stability of lubricant,activity of CGNs,controllable atomization and transportation methods,and intelligent formation of processing technology solutions.
