This paper presents a high-fidelity lumpedparameter(LP)thermal model(HF-LPTM)for permanent magnet synchronous machines(PMSMs)in electric vehicle(EV)applications,where various cooling techniques are considered,includin...This paper presents a high-fidelity lumpedparameter(LP)thermal model(HF-LPTM)for permanent magnet synchronous machines(PMSMs)in electric vehicle(EV)applications,where various cooling techniques are considered,including frame forced air/liquid cooling,oil jet cooling for endwinding,and rotor shaft cooling.To address the temperature misestimation in the LP thermal modelling due to assumptions of concentrated loss input and uniform heat flows,the developed HF-LPTM introduces two compensation thermal resistances for the winding and PM components,which are analytically derived from the multi-dimensional heat transfer equations and are robust against different load/thermal conditions.As validated by the finite element analysis method and experiments,the conventional LPTMs exhibit significant winding temperature deviations,while the proposed HF-LPTM can accurately predict both the midpoint and average temperatures.The developed HFLPTM is further used to assess the effectiveness of various cooling techniques under different scenarios,i.e.,steady-state thermal states under the rated load condition,and transient temperature profiles under city,freeway,and hybrid(city+freeway)driving cycles.Results indicate that no single cooling technique can maintain both winding and PM temperatures within safety limits.The combination of frame liquid cooling and oil jet cooling for end winding can sufficiently mitigate PMSM thermal stress in EV applications.展开更多
With a commitment to reduce emissions,and its investment in green technology bringing down global costs,China is emerging as the leader in fighting climate change.EVERYBODY knows that our world is getting hotter.They ...With a commitment to reduce emissions,and its investment in green technology bringing down global costs,China is emerging as the leader in fighting climate change.EVERYBODY knows that our world is getting hotter.They also know why.Pumping out pollutants has transformed our world into a greenhouse;heat from the sun is now trapped by a“dirty”atmosphere.展开更多
Beyond modern trade tensions and diplomatic milestones,Europe and China’s profound connection stems from a 3,000-year interplay of ideas,goods,and values,shaping their intertwined visions of governance,equality,and s...Beyond modern trade tensions and diplomatic milestones,Europe and China’s profound connection stems from a 3,000-year interplay of ideas,goods,and values,shaping their intertwined visions of governance,equality,and societal progress.展开更多
THE world should be celebrating the creation of the United Nations(UN)80 years ago.However,its very existence is threatened.China recognizes the UN as the core of the international system.The UN Charter is a legal tre...THE world should be celebrating the creation of the United Nations(UN)80 years ago.However,its very existence is threatened.China recognizes the UN as the core of the international system.The UN Charter is a legal treaty under which national governments freely agree to uphold values and principles of behaviour.As a manifestation of the principle of“the sovereign equality of members,”each has an equal vote in the General Assembly.展开更多
In the Internet of Things(IoT)based scenarios,the network may encounter significant issues related to energy and communication as a result of a progressively growing number of terminals.We introduce simultaneous wirel...In the Internet of Things(IoT)based scenarios,the network may encounter significant issues related to energy and communication as a result of a progressively growing number of terminals.We introduce simultaneous wireless power transfer(SWIPT)technology assisted by a reconfigurable intelligent surface(RIS)to counteract this challenge.Thus,the network’s flexibility and reliability will be further enhanced.According to this system architecture,the scattering-parameter-based communication model is introduced to disclose hardware features for an energy efficiency(EE)maximization problem.Specifically,the potential unauthorized demodulation is also considered in the problem formulation.To resolve the issue,an alternative strategy is utilized to optimize iteratively the coupled variables.In particular,the block coordinate descent(BCD)approach based on the Sherman-Morrison formula is proposed to solve the RIS subproblem.The numerical results prove the hardware effects cannot be dismissed lightly.Besides,the configuration of the RIS may impact the network performance directly.展开更多
THE people of Xinjiang have always needed to be resilient.Over four-hour flight time from Beijing,Xinjiang Uygur Autonomous Region is located on China’s western border.Historically,Xinjiang’s people have needed to h...THE people of Xinjiang have always needed to be resilient.Over four-hour flight time from Beijing,Xinjiang Uygur Autonomous Region is located on China’s western border.Historically,Xinjiang’s people have needed to hold steadfast against invaders while encouraging trade between China and central Asia,Europe and beyond.For 25 years until 2016,they also witnessed multiple atrocities perpetrated by separatists.展开更多
Belt conveyors are extensively utilized in mining and power industries.In a typical coal mine conveyor system,coal is transported over distances exceeding 2 km,involving more than 20000 idlers,which far exceeds a reas...Belt conveyors are extensively utilized in mining and power industries.In a typical coal mine conveyor system,coal is transported over distances exceeding 2 km,involving more than 20000 idlers,which far exceeds a reasonable manual inspection capacity.Given that idlers typically have a lifespan of 1-2 years,there is an urgent need for a rapid,cost-effective,and intelligent safety monitoring system.However,current embedded systems face prohibitive replacement costs,while conventional monitoring technologies suffer from inefficiency at low rotational speeds and lack systematic structural optimization frameworks for diverse idler types and parameters.To address these challenges,this paper introduces an integrated,on-site detachable self-powered idler condition monitoring system(ICMS).This system combines energy harvesting based on the magnetic modulation technology with wireless condition monitoring capabilities.Specifically,it develops a data-driven model integrating convolutional neural networks(CNNs) with genetic algorithms(GAs).The conventional testing results show that the data-driven model not only significantly accelerates the parameter response time,but also achieves a prediction accuracy of 92.95%.The in-situ experiments conducted in coal mines demonstrate the system's reliability and monitoring functionality under both no-load and fullload conditions.This research provides an innovative self-powered condition monitoring solution and develops an efficient data-driven model,offering feasible online monitoring approaches for smart mine construction.展开更多
In this paper,we investigate the problem of fast spectrum sharing in vehicle-to-everything com-munication.In order to improve the spectrum effi-ciency of the whole system,the spectrum of vehicle-to-infrastructure link...In this paper,we investigate the problem of fast spectrum sharing in vehicle-to-everything com-munication.In order to improve the spectrum effi-ciency of the whole system,the spectrum of vehicle-to-infrastructure links is reused by vehicle-to-vehicle links.To this end,we model it as a problem of deep reinforcement learning and tackle it with prox-imal policy optimization.A considerable number of interactions are often required for training an agent with good performance,so simulation-based training is commonly used in communication networks.Nev-ertheless,severe performance degradation may occur when the agent is directly deployed in the real world,even though it can perform well on the simulator,due to the reality gap between the simulation and the real environments.To address this issue,we make prelim-inary efforts by proposing an algorithm based on meta reinforcement learning.This algorithm enables the agent to rapidly adapt to a new task with the knowl-edge extracted from similar tasks,leading to fewer in-teractions and less training time.Numerical results show that our method achieves near-optimal perfor-mance and exhibits rapid convergence.展开更多
COVID-19 placed increased pressure and urgency for effective cost management,resulting in unprecedented financial strains for hospitals.The pandemic also became a catalyst for accelerating digital transformation to im...COVID-19 placed increased pressure and urgency for effective cost management,resulting in unprecedented financial strains for hospitals.The pandemic also became a catalyst for accelerating digital transformation to improve operations and services in the healthcare industry.Morningdale Hospital is a large and reputable general hospital with a long history in the U.K.You are an intern in the Finance Department of the Hospital.The CEO has asked you to complete a patient-level cost analysis of endoscopic procedures in the Gastrointestinal Department.In your final report,you plan to include a SWOT analysis and a cost analysis using Activity-Based Costing accounting method.展开更多
Carbon nanotubes(CNTs)have garnered great attention in recent years due to their outstanding electrical,thermal,and mechanical properties.The incorporation of small amounts of CNTs in polymers can substantially improv...Carbon nanotubes(CNTs)have garnered great attention in recent years due to their outstanding electrical,thermal,and mechanical properties.The incorporation of small amounts of CNTs in polymers can substantially improve the sensitivity of the polymer's electrical conductivity.This paper presents a modified Maxwell model to evaluate the electrical conductivity of CNTs-filled polymer composites by introducing a transition zone to account for the tunneling effect.In this modified Maxwell model,the CNTs-filled polymer composite is modeled as a three-phase composite,consisting of a matrix(polymer),inclusions(CNTs),and a transition zone(tunneling zone).The effective electrical conductivity(EEC)of the composite is calculated based on the volume fractions and electrical conductivities of the matrix,inclusions,and transition zone.The model's validity is confirmed through the use of available test data,which demonstrates its capability to accurately capture the nonlinear conductivity behavior observed in CNTs-polymer composites.This study offers valuable insights into the design of high-performance conductive polymer nanocomposites,and enhances the understanding of electrical conduction mechanisms in CNT-dispersed polymer composites.展开更多
Low-carbon smart parks achieve selfbalanced carbon emission and absorption through the cooperative scheduling of direct current(DC)-based distributed photovoltaic,energy storage units,and loads.Direct current power li...Low-carbon smart parks achieve selfbalanced carbon emission and absorption through the cooperative scheduling of direct current(DC)-based distributed photovoltaic,energy storage units,and loads.Direct current power line communication(DC-PLC)enables real-time data transmission on DC power lines.With traffic adaptation,DC-PLC can be integrated with other complementary media such as 5G to reduce transmission delay and improve reliability.However,traffic adaptation for DC-PLC and 5G integration still faces the challenges such as coupling between traffic admission control and traffic partition,dimensionality curse,and the ignorance of extreme event occurrence.To address these challenges,we propose a deep reinforcement learning(DRL)-based delay sensitive and reliable traffic adaptation algorithm(DSRTA)to minimize the total queuing delay under the constraints of traffic admission control,queuing delay,and extreme events occurrence probability.DSRTA jointly optimizes traffic admission control and traffic partition,and enables learning-based intelligent traffic adaptation.The long-term constraints are incorporated into both state and bound of drift-pluspenalty to achieve delay awareness and enforce reliability guarantee.Simulation results show that DSRTA has lower queuing delay and more reliable quality of service(QoS)guarantee than other state-of-the-art algorithms.展开更多
Cyber-physical systems(CPSs)are regarded as the backbone of the fourth industrial revolution,in which communication,physical processes,and computer technology are integrated.In modern industrial systems,CPSs are widel...Cyber-physical systems(CPSs)are regarded as the backbone of the fourth industrial revolution,in which communication,physical processes,and computer technology are integrated.In modern industrial systems,CPSs are widely utilized across various domains,such as smart grids,smart healthcare systems,smart vehicles,and smart manufacturing,among others.Due to their unique spatial distribution,CPSs are highly vulnerable to cyber-attacks,which may result in severe performance degradation and even system instability.Consequently,the security concerns of CPSs have attracted significant attention in recent years.In this paper,a comprehensive survey on the security issues of CPSs under cyber-attacks is provided.Firstly,mathematical descriptions of various types of cyberattacks are introduced in detail.Secondly,two types of secure estimation and control processing schemes,including robust methods and active methods,are reviewed.Thirdly,research findings related to secure control and estimation problems for different types of CPSs are summarized.Finally,the survey is concluded by outlining the challenges and suggesting potential research directions for the future.展开更多
In offshore maritime communication sys-tems,base stations(BSs)are employed along the coastline to provide high-speed data service for ves-sels in coastal sea areas.To ensure the line-of-sight propagation of BS-vessel ...In offshore maritime communication sys-tems,base stations(BSs)are employed along the coastline to provide high-speed data service for ves-sels in coastal sea areas.To ensure the line-of-sight propagation of BS-vessel links,high transceiver an-tenna height is required,which limits the number of geographically available sites for BS deployment,and imposes a high cost for realizing effective wide-area coverage.In this paper,the joint user association and power allocation(JUAPA)problem is investigated to enhance the coverage of offshore maritime systems.By exploiting the characteristics of network topology as well as vessels’motion in offshore communica-tions,a multi-period JUAPA problem is formulated to maximize the number of ships that can be simultane-ously served by the network.This JUAPA problem is intrinsically non-convex and subject to mixed-integer constraints,which is difficult to solve either analyt-ically or numerically.Hence,we propose an iterative augmentation based framework to efficiently select the active vessels,where the JUAPA scheme is iteratively optimized by the network for increasing the number of the selected vessels.More specifically,in each itera-tion,the user association variables and power alloca-tion variables are determined by solving two separate subproblems,so that the JUAPA strategy can be up-dated in a low-complexity manner.The performance of the proposed JUAPA method is evaluated by exten-sive simulation,and numerical results indicate that it can effectively increase the number of vessels served by the network,and thus enhances the coverage of off-shore systems.展开更多
文摘This paper presents a high-fidelity lumpedparameter(LP)thermal model(HF-LPTM)for permanent magnet synchronous machines(PMSMs)in electric vehicle(EV)applications,where various cooling techniques are considered,including frame forced air/liquid cooling,oil jet cooling for endwinding,and rotor shaft cooling.To address the temperature misestimation in the LP thermal modelling due to assumptions of concentrated loss input and uniform heat flows,the developed HF-LPTM introduces two compensation thermal resistances for the winding and PM components,which are analytically derived from the multi-dimensional heat transfer equations and are robust against different load/thermal conditions.As validated by the finite element analysis method and experiments,the conventional LPTMs exhibit significant winding temperature deviations,while the proposed HF-LPTM can accurately predict both the midpoint and average temperatures.The developed HFLPTM is further used to assess the effectiveness of various cooling techniques under different scenarios,i.e.,steady-state thermal states under the rated load condition,and transient temperature profiles under city,freeway,and hybrid(city+freeway)driving cycles.Results indicate that no single cooling technique can maintain both winding and PM temperatures within safety limits.The combination of frame liquid cooling and oil jet cooling for end winding can sufficiently mitigate PMSM thermal stress in EV applications.
文摘With a commitment to reduce emissions,and its investment in green technology bringing down global costs,China is emerging as the leader in fighting climate change.EVERYBODY knows that our world is getting hotter.They also know why.Pumping out pollutants has transformed our world into a greenhouse;heat from the sun is now trapped by a“dirty”atmosphere.
文摘Beyond modern trade tensions and diplomatic milestones,Europe and China’s profound connection stems from a 3,000-year interplay of ideas,goods,and values,shaping their intertwined visions of governance,equality,and societal progress.
文摘THE world should be celebrating the creation of the United Nations(UN)80 years ago.However,its very existence is threatened.China recognizes the UN as the core of the international system.The UN Charter is a legal treaty under which national governments freely agree to uphold values and principles of behaviour.As a manifestation of the principle of“the sovereign equality of members,”each has an equal vote in the General Assembly.
文摘In the Internet of Things(IoT)based scenarios,the network may encounter significant issues related to energy and communication as a result of a progressively growing number of terminals.We introduce simultaneous wireless power transfer(SWIPT)technology assisted by a reconfigurable intelligent surface(RIS)to counteract this challenge.Thus,the network’s flexibility and reliability will be further enhanced.According to this system architecture,the scattering-parameter-based communication model is introduced to disclose hardware features for an energy efficiency(EE)maximization problem.Specifically,the potential unauthorized demodulation is also considered in the problem formulation.To resolve the issue,an alternative strategy is utilized to optimize iteratively the coupled variables.In particular,the block coordinate descent(BCD)approach based on the Sherman-Morrison formula is proposed to solve the RIS subproblem.The numerical results prove the hardware effects cannot be dismissed lightly.Besides,the configuration of the RIS may impact the network performance directly.
文摘THE people of Xinjiang have always needed to be resilient.Over four-hour flight time from Beijing,Xinjiang Uygur Autonomous Region is located on China’s western border.Historically,Xinjiang’s people have needed to hold steadfast against invaders while encouraging trade between China and central Asia,Europe and beyond.For 25 years until 2016,they also witnessed multiple atrocities perpetrated by separatists.
基金supported by the National Natural Science Foundation of China(Nos.12172248,12302022,12021002,and 12132010)the Tianjin Research Program of Application Foundation and Advanced Technology of China(No.23JCZDJC00950)。
文摘Belt conveyors are extensively utilized in mining and power industries.In a typical coal mine conveyor system,coal is transported over distances exceeding 2 km,involving more than 20000 idlers,which far exceeds a reasonable manual inspection capacity.Given that idlers typically have a lifespan of 1-2 years,there is an urgent need for a rapid,cost-effective,and intelligent safety monitoring system.However,current embedded systems face prohibitive replacement costs,while conventional monitoring technologies suffer from inefficiency at low rotational speeds and lack systematic structural optimization frameworks for diverse idler types and parameters.To address these challenges,this paper introduces an integrated,on-site detachable self-powered idler condition monitoring system(ICMS).This system combines energy harvesting based on the magnetic modulation technology with wireless condition monitoring capabilities.Specifically,it develops a data-driven model integrating convolutional neural networks(CNNs) with genetic algorithms(GAs).The conventional testing results show that the data-driven model not only significantly accelerates the parameter response time,but also achieves a prediction accuracy of 92.95%.The in-situ experiments conducted in coal mines demonstrate the system's reliability and monitoring functionality under both no-load and fullload conditions.This research provides an innovative self-powered condition monitoring solution and develops an efficient data-driven model,offering feasible online monitoring approaches for smart mine construction.
基金L.Liang was supported in part by the Natural Science Foundation of Jiangsu Province under Grant BK20220810in part by the National Natural Science Foundation of China under Grant 62201145 and Grant 62231019S.Jin was supported in part by the National Natural Science Foundation of China(NSFC)under Grants 62261160576,62341107,61921004。
文摘In this paper,we investigate the problem of fast spectrum sharing in vehicle-to-everything com-munication.In order to improve the spectrum effi-ciency of the whole system,the spectrum of vehicle-to-infrastructure links is reused by vehicle-to-vehicle links.To this end,we model it as a problem of deep reinforcement learning and tackle it with prox-imal policy optimization.A considerable number of interactions are often required for training an agent with good performance,so simulation-based training is commonly used in communication networks.Nev-ertheless,severe performance degradation may occur when the agent is directly deployed in the real world,even though it can perform well on the simulator,due to the reality gap between the simulation and the real environments.To address this issue,we make prelim-inary efforts by proposing an algorithm based on meta reinforcement learning.This algorithm enables the agent to rapidly adapt to a new task with the knowl-edge extracted from similar tasks,leading to fewer in-teractions and less training time.Numerical results show that our method achieves near-optimal perfor-mance and exhibits rapid convergence.
文摘COVID-19 placed increased pressure and urgency for effective cost management,resulting in unprecedented financial strains for hospitals.The pandemic also became a catalyst for accelerating digital transformation to improve operations and services in the healthcare industry.Morningdale Hospital is a large and reputable general hospital with a long history in the U.K.You are an intern in the Finance Department of the Hospital.The CEO has asked you to complete a patient-level cost analysis of endoscopic procedures in the Gastrointestinal Department.In your final report,you plan to include a SWOT analysis and a cost analysis using Activity-Based Costing accounting method.
基金Project supported by the National Natural Science Foundation of China(Nos.11972203 and 11572162)the Science and Technology Innovation 2025 Major Project of Ningbo City of China(No.2022Z209)Ningbo Key Technology Breakthrough Plan Project of“Science and Technology Innovation Yongjiang 2035”(No.2024Z256)。
文摘Carbon nanotubes(CNTs)have garnered great attention in recent years due to their outstanding electrical,thermal,and mechanical properties.The incorporation of small amounts of CNTs in polymers can substantially improve the sensitivity of the polymer's electrical conductivity.This paper presents a modified Maxwell model to evaluate the electrical conductivity of CNTs-filled polymer composites by introducing a transition zone to account for the tunneling effect.In this modified Maxwell model,the CNTs-filled polymer composite is modeled as a three-phase composite,consisting of a matrix(polymer),inclusions(CNTs),and a transition zone(tunneling zone).The effective electrical conductivity(EEC)of the composite is calculated based on the volume fractions and electrical conductivities of the matrix,inclusions,and transition zone.The model's validity is confirmed through the use of available test data,which demonstrates its capability to accurately capture the nonlinear conductivity behavior observed in CNTs-polymer composites.This study offers valuable insights into the design of high-performance conductive polymer nanocomposites,and enhances the understanding of electrical conduction mechanisms in CNT-dispersed polymer composites.
基金supported by the Science and Technology Project of State Grid Corporation of China under grant 52094021N010(5400-202199534A-0-5-ZN)。
文摘Low-carbon smart parks achieve selfbalanced carbon emission and absorption through the cooperative scheduling of direct current(DC)-based distributed photovoltaic,energy storage units,and loads.Direct current power line communication(DC-PLC)enables real-time data transmission on DC power lines.With traffic adaptation,DC-PLC can be integrated with other complementary media such as 5G to reduce transmission delay and improve reliability.However,traffic adaptation for DC-PLC and 5G integration still faces the challenges such as coupling between traffic admission control and traffic partition,dimensionality curse,and the ignorance of extreme event occurrence.To address these challenges,we propose a deep reinforcement learning(DRL)-based delay sensitive and reliable traffic adaptation algorithm(DSRTA)to minimize the total queuing delay under the constraints of traffic admission control,queuing delay,and extreme events occurrence probability.DSRTA jointly optimizes traffic admission control and traffic partition,and enables learning-based intelligent traffic adaptation.The long-term constraints are incorporated into both state and bound of drift-pluspenalty to achieve delay awareness and enforce reliability guarantee.Simulation results show that DSRTA has lower queuing delay and more reliable quality of service(QoS)guarantee than other state-of-the-art algorithms.
文摘Cyber-physical systems(CPSs)are regarded as the backbone of the fourth industrial revolution,in which communication,physical processes,and computer technology are integrated.In modern industrial systems,CPSs are widely utilized across various domains,such as smart grids,smart healthcare systems,smart vehicles,and smart manufacturing,among others.Due to their unique spatial distribution,CPSs are highly vulnerable to cyber-attacks,which may result in severe performance degradation and even system instability.Consequently,the security concerns of CPSs have attracted significant attention in recent years.In this paper,a comprehensive survey on the security issues of CPSs under cyber-attacks is provided.Firstly,mathematical descriptions of various types of cyberattacks are introduced in detail.Secondly,two types of secure estimation and control processing schemes,including robust methods and active methods,are reviewed.Thirdly,research findings related to secure control and estimation problems for different types of CPSs are summarized.Finally,the survey is concluded by outlining the challenges and suggesting potential research directions for the future.
基金supported by the National Key Research and Development Program of China under Grant 2018YFA0701601by the Program of Jiangsu Province under Grant NTACT-2024-Z-001.
文摘In offshore maritime communication sys-tems,base stations(BSs)are employed along the coastline to provide high-speed data service for ves-sels in coastal sea areas.To ensure the line-of-sight propagation of BS-vessel links,high transceiver an-tenna height is required,which limits the number of geographically available sites for BS deployment,and imposes a high cost for realizing effective wide-area coverage.In this paper,the joint user association and power allocation(JUAPA)problem is investigated to enhance the coverage of offshore maritime systems.By exploiting the characteristics of network topology as well as vessels’motion in offshore communica-tions,a multi-period JUAPA problem is formulated to maximize the number of ships that can be simultane-ously served by the network.This JUAPA problem is intrinsically non-convex and subject to mixed-integer constraints,which is difficult to solve either analyt-ically or numerically.Hence,we propose an iterative augmentation based framework to efficiently select the active vessels,where the JUAPA scheme is iteratively optimized by the network for increasing the number of the selected vessels.More specifically,in each itera-tion,the user association variables and power alloca-tion variables are determined by solving two separate subproblems,so that the JUAPA strategy can be up-dated in a low-complexity manner.The performance of the proposed JUAPA method is evaluated by exten-sive simulation,and numerical results indicate that it can effectively increase the number of vessels served by the network,and thus enhances the coverage of off-shore systems.
