The flammability of magnesium alloys continues to be a significant barrier to their extensive application,and alloying with rare earth elements(REs)is an effective way to enhance the ignition and fire resistance of Mg...The flammability of magnesium alloys continues to be a significant barrier to their extensive application,and alloying with rare earth elements(REs)is an effective way to enhance the ignition and fire resistance of Mg alloys.Three commercial as-extruded Mg alloys(AZ80 and two Mg-RE alloys:EZ30K and WE43)were directly exposed to flame heating for revealing the evolutions of microstructure and mechanical properties,which is valuable in assessing the post-fire residual service performance of Mg alloy components.Results show that secondary phase dissolution,grain growth,grain boundary melting,alloy melting,and defects generation successively occur during the heating process.After short-term heating for 30 s,the elongation of AZ80 alloy increases significantly by 214%,from 3.82%to 12.01%,with minimal change in strength compared to the initial unheated state.This transformation is attributed to the recovery,grain growth,Mg17Al12 dissolution and dislocation density reduction.Conversely,EZ30K and WE43 alloys exhibit minimal changes in mechanical properties after short-term heating for 60 s,attributed to the pinning effect of REs.However,in subsequent heating states,resolidified microstructure and the presence of defects lead to a noteworthy decrease in both strength and elongation.Among these three alloys,the fire resistance follows this ranking:EZ30K>WE43>AZ80,primarily due to the high thermal conductivity of EZ30K alloy and the thermal stability improved by the addition of REs.展开更多
TiN coatings were prepared by the novel dual-stage high power impulse magnetron sputtering(HIPIMS)technique under different deposition time conditions,and the effects of microstructure and stress state at different co...TiN coatings were prepared by the novel dual-stage high power impulse magnetron sputtering(HIPIMS)technique under different deposition time conditions,and the effects of microstructure and stress state at different coating growth stages on the mechanical,tribological,and corrosion resistance performance of the coatings were analyzed.Results show that with the prolongation of deposition time from 30 min to 120 min,the surface structure of TiN coating exhibits a round cell structure with tightly doped small and large particles,maintaining the atomic stacking thickening mechanism of deposition-crystallization-growth.When the deposition time increases from 90 min to 120 min,the coating thickness increases from 3884 nm to 4456 nm,and the stress state of coating undergoes the compression-tension transition.When the deposition time is 90 min,TiN coating structure is dense and suffers relatively small compressive stress of−0.54 GPa.The coating has high hardness and elastic modulus,which are 27.5 and 340.2 GPa,respectively.Meanwhile,good tribological properties(average friction coefficient of 0.52,minimum wear rate of 1.68×10^(−4)g/s)and fine corrosion resistance properties(minimum corrosion current density of 1.0632×10^(−8)A·cm^(−2),minimum corrosion rate of 5.5226×10^(−5)mm·A^(−1))can also be obtained for the coatings.展开更多
In the aerospace field, residual stress directly affects the strength, fatigue life and dimensional stability of thin-walled structural components, and is a key factor to ensure flight safety and reliability. At prese...In the aerospace field, residual stress directly affects the strength, fatigue life and dimensional stability of thin-walled structural components, and is a key factor to ensure flight safety and reliability. At present, research on residual stress at home and abroad mainly focuses on the optimization of traditional detection technology, stress control of manufacturing process and service performance evaluation, among which research on residual stress detection methods mainly focuses on the improvement of the accuracy, sensitivity, reliability and other performance of existing detection methods, but it still faces many challenges such as extremely small detection range, low efficiency, large error and limited application range.展开更多
In the upcoming B5G/6G era,Virtual Reality(VR)over wireless has become a typical application,which is an inevitable trend in the development of video.However,in immersive and interactive VR experiences,VR services typ...In the upcoming B5G/6G era,Virtual Reality(VR)over wireless has become a typical application,which is an inevitable trend in the development of video.However,in immersive and interactive VR experiences,VR services typically exhibit high delay,while simultaneously posing challenges for the energy consumption of local devices.To address these issues,this paper aims to improve the performance of VR service in the edge-terminal cooperative system.Specifically,we formulate a joint Caching,Computing,and Communication(3C)VR service policy problem by optimizing the weighted sum of the total VR delivery delay and the energy consumption of local devices.To design the optimal VR service policy,the optimization problem is decoupled into three independent subproblems to be solved separately.To improve the caching efficiency within the network,a Bert-based user interest analysis method is first proposed to accurately characterize the content request behavior.Based on this,a service cost minimum-maximization problem is formulated under the consideration of performance fairness among users.Then,the joint caching and computing scheme is derived for each user with a given allocation of communication resources while a bisection-based communication scheme is acquired with the given information on the joint caching and computing policy.With alternative optimization,an optimal policy for joint 3C based on user interest can be finally obtained.Simulation results are presented to demonstrate the superiority of the proposed user interest-aware caching scheme and the effectiveness of the joint 3C optimization policy while considering user fairness.Our code is available at https://github.com/mrfuqaq1108/Interest-Aware-Joint-3C-Optimization.展开更多
h-BN rods modified low-carbon alumina-carbon(Al_(2)O_(3)-C)refractories were prepared,and the effect of h-BN rod addition on the high-temperature properties was investigated and compared with commercial h-BN flake,car...h-BN rods modified low-carbon alumina-carbon(Al_(2)O_(3)-C)refractories were prepared,and the effect of h-BN rod addition on the high-temperature properties was investigated and compared with commercial h-BN flake,carbon black,and carbon nanotubes additives.The results demonstrated that Al_(2)O_(3)-C refractories containing h-BN rods exhibited optimal high-temperature service performances,including 25%higher hot modulus of rupture,21.3%higher thermal shock strength residual ratio,20.9%lower in oxidation and 44.3%less in slag corrosion,compared to the counterpart specimens without additives.Moreover,benefiting from the synergistic enhancement of the rod-like h-BN and in-situ generated SiC whiskers,the high-temperature service performances of h-BN rods containing specimens outperformed counterpart specimens containing commercial h-BN flake,carbon black,and carbon nanotubes,respectively.展开更多
We successfully fabricated partial Y substituted NdY-Fe-B magnets with nominal compositions of(Nd_(1-x)Y_(x))_(13.80)Fe_(ba1)Al_(0.24)Cu_(0.1)B_(6.04)(at%,x=0,0.1,0.2,0.3,0.4) by powder metallurgy process and the magn...We successfully fabricated partial Y substituted NdY-Fe-B magnets with nominal compositions of(Nd_(1-x)Y_(x))_(13.80)Fe_(ba1)Al_(0.24)Cu_(0.1)B_(6.04)(at%,x=0,0.1,0.2,0.3,0.4) by powder metallurgy process and the magnetic properties as well as service performances of the magnets were also systematically investigated.The phase constituents of the magnets have no obvious variation within the whole range of Y content,while the main phase grains form in-situ core-shell structure where Y gathers in the core and Nd mainly distributes in the shell.Compared with pure Nd-Fe-B magnets,the magnetic performances of Y substituted magnets slightly decrease on account of the poor intrinsic magnetic properties of Y_(2)Fe_(14)B.Fortunately,the μ_(O)M_(r),μ_(O)H_(cj) and(BH)_(max) of the 20 at% Y magnet still remain at a high level of 1.325 kG,1.173 kOe and 342.884 kj/m^(3),which approaches the performances of commercial N45-grade magnet.The service performances of Y substituted magnets indicate that though the surface corrosion products and Vickers hardness of the NdY-Fe-B magnets increase to a certain extent compared to Nd-Fe-B,the magnets with Y substitution still display relatively good service performances.Therefore,on the basis of sacrificing little partial magnetic and service performances,Y substituted Nd can still prepare NdY-Fe-B medium-grade magnets.By this way,we achieve the balanced utilization of rare earth resources,which has significant meanings for the industry and scientific research.展开更多
Design change is an inevitable part of the product development process.This study proposes an improved binary multi‐objective PSO algorithm guided by problem char-acteristics(P‐BMOPSO)to solve the optimisation probl...Design change is an inevitable part of the product development process.This study proposes an improved binary multi‐objective PSO algorithm guided by problem char-acteristics(P‐BMOPSO)to solve the optimisation problem of complex product change plan considering service performance.Firstly,a complex product multi‐layer network with service performance is established for the first time to reveal the impact of change effect propagation on the product service performance.Secondly,the concept of service performance impact(SPI)is defined by decoupling the impact of strongly associated nodes on the service performance in the process of change affect propagation.Then,a triple‐objective selection model of change nodes is established,which includes the three indicators:SPI degree,change cost,and change time.Furthermore,an integer multi‐objective particle swarm optimisation algorithm guided by problem characteristics is developed to solve the model above.Experimental results on the design change problem of a certain type of Skyworth TV verify the effectiveness of the established optimisation model and the proposed P‐BMOPSO algorithm.展开更多
An architecture for online discovery quantitative models system of service performance management is proposed. The system is capable of constructing the quantitative models without prior knowledge of the managed eleme...An architecture for online discovery quantitative models system of service performance management is proposed. The system is capable of constructing the quantitative models without prior knowledge of the managed elements. The model can be updated continuously in response to the changes made in provider configurations and the evolution of business demands. Due to the existence of strong correlation between the distributed service metrics and response times, linear and hyper-linear quantitative models are constructed, which respectively, use stepwise multiple linear regression algorithm. The simulation results show the effectiveness of a quantitative model constructing system and model constructing algorithms.展开更多
The rapid development of iron and steel metallurgy technology has promoted the continuous innovation and iteration of carbon-containing refractories for clean steel smelting.To meet the high-quality requirements for c...The rapid development of iron and steel metallurgy technology has promoted the continuous innovation and iteration of carbon-containing refractories for clean steel smelting.To meet the high-quality requirements for clean steel production and full exploit the performance advantages of carbon-containing refractories in dynamic smelting environment,it is necessary to explore the role of graphite and modified graphite in carbon-containing refractories.Based on this,graphite surface modification methods,including surfactants,surface oxidation,and surface coating,and their applications in carbon-containing refractories are reviewed.The advantages and disadvantages of each method are analyzed for practical use.Furthermore,combined with the existing problems,the application prospect of improved graphite in carbon-containing refractories is discussed.展开更多
Asphalt pavement is the main type of pavement structure in China,and it accounts for more than 90%of the large-scale road network.As the service life of asphalt pavement increases,the demand for maintenance is increas...Asphalt pavement is the main type of pavement structure in China,and it accounts for more than 90%of the large-scale road network.As the service life of asphalt pavement increases,the demand for maintenance is increasing significantly.Accurately revealing the degradation mechanism and predicting the performance of asphalt pavement is the basis for the scientific maintenance decisions.Meanwhile,it is also beneficial for road construction planning and resource allocation.Based on numerous current studies,this review firstly provides a comprehensive summary of the internal factors such as structure and material,as well as external factors such as environment,load,and construction,that impact the performance of asphalt pavement.Simultaneously,the degradation trend of asphalt pavement performance under intricate conditions is also clarified.Furthermore,the commonly used performance prediction models of asphalt pavement are analyzed,such as deterministic methods,uncertainty methods,machine learning,dynamic methods and so on.And their applicability and limitations are also summarized.Finally,considering the complexity of predicting asphalt pavement performance,this review identifies key challenges and future prospects in this area.This provides theoretical support for accurately predicting the performance degeneration of asphalt pavement,making scientific maintenance decisions,and promoting the durability improvement of asphalt pavement.展开更多
Low cost and high abundance rare earth elements Y and Ce have attracted tremendous interests of the industrial and scientific societies for fabricating the highly cost-performance efficient rare earth permanent magnet...Low cost and high abundance rare earth elements Y and Ce have attracted tremendous interests of the industrial and scientific societies for fabricating the highly cost-performance efficient rare earth permanent magnets.However,the effect of separate replacement of Nd by Y or Ce on the performances of NdFeB-type magnet under the same atomic ratio and preparation conditions is still unclear.In this work,we systematically investigated the magnetic properties,thermal stabilities and service performances of(Nd_(0.8)Y_(0.2))_(13.80)Fe_(bal)Al_(0.24)Cu_(0.1)B_(6.04)(atomic fraction,denoted as 20 Y)and(Nd_(0.8)Ce_(0.2))_(13.80)Fe_(bal)Al_(0.24)Cu_(0.1)B_(6.04)(atomic fraction,denoted as 20 Ce)magnets.The results demonstrate that theμ_(0)M_(r),μ_(0)H_(c)and(BH)_(max)of 20 Y magnet are respectively 1.325 T,1.173 T and 343.467 kJ/m^(3),which are comprehensively higher than those of 20 Ce magnet(μ_(0)M_(r)=1.310 T,μ_(0)H_(c)=0.948 T,(BH)_(max)=321.105 kJ/m^(3)).Moreover,the 20 Y magnet has higher thermal stability compared with 20 Ce magnet which is favorable for the magnetic performances at elevated temperatures.The investigation of micro structure and elemental distribution indicates that the excellent magnetic performance s of NdY-Fe-B magnet can be attributed not only to the preferable intrinsic properties4πM_(s),H_(s)and T_(c)of Y_(2)Fe_(14)B,but also to the in-situ co re-shell structure of the 2:14:1 matrix phase grain with Yrich core and Nd-rich shell,along with the thicker grain boundary layer between the adjacent matrix phase grains in NdY-Fe-B magnet.Furthermore,the 20 Y magnet exhibits better mechanical property and higher corrosion resistance than 20 Ce magnet,which are helpful for prolonging the service life of the magnet in practical application.展开更多
This paper focuses on solving the modeling issues of monitoring system service performance based on the network calculus theory.First,we formulate the service model of the smart grid monitoring system.Then,we derive t...This paper focuses on solving the modeling issues of monitoring system service performance based on the network calculus theory.First,we formulate the service model of the smart grid monitoring system.Then,we derive the flow arrival curve based on the incremental process related functions.Next,we develop flow arrival curves for the case of the incremental process being a fractional Gaussian process,and then we obtain the generalized Cauchy process.Three technical theorems related to network calculus are presented as our main results.Mathematically,the variance of arrival flow for the continuous time case is derived.Assuming that the incremental process of network flow is a Gaussian stationary process,and given the auto-correlation function of the incremental process with violation probability,the formula of the arrival curve is derived.In addition,the overall flow variance under the discrete time case is explicitly derived.The theoretical results are evaluated in smart grid applications.Simulations indicate that the generalized Cauchy process outperforms the fractional Gaussian process for our considered problem.展开更多
In order to quantitatively describe the local corrosion process of steel bars in cracked concrete area, a new two-staged utility model is established, and the effect of transverse cracks on the reinforcement corrosion...In order to quantitatively describe the local corrosion process of steel bars in cracked concrete area, a new two-staged utility model is established, and the effect of transverse cracks on the reinforcement corrosion is analyzed from the angle of long-term service performance evaluation for reinforced concrete structure. Moreover, based on the principle of spectral analysis for environmental action of concrete, an equivalent relationship is established between the corrosion rate in the natural environment and that under the standard temperature and relative humidity condition according to the principle of equivalent annual corrosion depth. Comparison between the inspection results from some references and the calculated values by the two- staged utility model validates the feasibility of the proposed model. The model was applied to Chinese Railway Track System （CRTS） Ⅱ ballastless track slab with transverse dummy joints, from which satisfactory results of corrosion degree of steel bars were obtained.展开更多
Purpose–This study aims to investigate the service performances of a new full-section asphalt concrete waterproof sealing structure(FSACWSS)for the high-speed railway subgrade through on-site tracking,monitoring and ...Purpose–This study aims to investigate the service performances of a new full-section asphalt concrete waterproof sealing structure(FSACWSS)for the high-speed railway subgrade through on-site tracking,monitoring and post-construction investigation.Design/methodology/approach–Based on the working state of the waterproof sealing structure,the main functional characteristics were analyzed,and a kind of roller-compacted high elastic modulus asphalt concrete(HEMAC)was designed and evaluated by several groups of laboratory tests.It is applied to an engineering test section,and the long-term performance monitoring and subgrade dynamic performance testing system were installed to track and monitor working performances of the test section and the adjacent contrast section with fiber-reinforced concrete.Findings–Results show that both the dynamic performance of the track structure and the subgrade in the test section meet the requirements of the specification limits.The water content in the subgrade of the test section is maintained at 8–18%,which is less affected by the weather.However,the water content in the subgrade bed of the contrast section is 10–35%,which fluctuates significantly with the weather.The heat absorption effect of asphalt concrete in the test section makes the temperature of the subgrade at the shoulder larger than that in the contrastive section.The monitoring value of the subgrade vertical deformation in the test section is slightly larger than that in the contrastive section,but all of them meet the limit requirements.The asphalt concrete in the test section is in good contact with the base,and there are no diseases such as looseness or spalling.Only a number of cracks are found at the joints of the base plates.However,there are more longitudinal and lateral cracks in the contrastive section,which seriously affects the waterproof and sealing effects.Besides,the asphalt concrete is easier to repair,featuring good maintainability.Originality/value–This research can provide a basis for popularization and application of the asphalt concrete waterproof sealing structure in high-speed railways.展开更多
As an important part of steel bridge deck,the engineering quality and service condition of steel bridge deck pavement(SBDP)directly affects the capacity and operational efficiency of the bridge.This paper reviews the ...As an important part of steel bridge deck,the engineering quality and service condition of steel bridge deck pavement(SBDP)directly affects the capacity and operational efficiency of the bridge.This paper reviews the history of the development of SBDP in China over the past 20 years from the exploration stage,rapid development stage and prosperity stage.The development and application of SBDP at different stages are discussed in terms of materials,structure,design,performance evaluation,maintenance and rehabilitation,respectively.The advantages and disadvantages of different pavement materials and structures,and the application of different research methods are summarized.The review shows that the improvement of pavement materials and structures and the development of new materials should be further studied on the multi-scale to enhance the durability of pavement materials,so as to extend the service life of pavements.The design method of SBDP related to the synergistic effect of vehicle,pavement and bridge should be established,and the design concept and method standard of rigid base pavement structure should be improved and formulate a complete design standard.In addition,multi-disease intelligent identification system and equipment should be studied to track the entire course of disease development in real time.And it is necessary to develop appropriate algorithms to select and classify the complex data of disease and maintenance history.展开更多
With the growing environmental concerns, green supply chain management （GSCM） is gaining significant attention in the construction industry. Tracking and monitoring the environmental effects brought forth by the par...With the growing environmental concerns, green supply chain management （GSCM） is gaining significant attention in the construction industry. Tracking and monitoring the environmental effects brought forth by the participating members along a supply chain is important to GSCM. The GreenSCOR model developed by the Supply Chain Council provides a generic framework for measuring the total carbon footprint and environmental footprint in a supply chain. The model is based on the Supply Chain Operations Reference （SCOR） model, which represents a supply chain network in a hierarchically structured manner. This paper describes the GreenSCOR framework and its potential application to the construction industry. This paper also presents a web services approach to incorporate the GreenSCOR model to the implementation of collaborative information systems. Each process element in the SCOR model is represented and delivered as individual web service units, which can be reused and integrated using standard web services technologies. The service units are combined and managed in a prototype web service collaborative framework, called SC Collaborator, which is designed and developed for supporting construction supply chain management. An illustrative example is presented to demonstrate the implementation of the GreenSCOR-based SC Collaborator framework.展开更多
The Ministry of Education and the State Council Information Office have named Renmin University of China as one of the human rights national education and training bases. This shows the full affirmation and trust in t...The Ministry of Education and the State Council Information Office have named Renmin University of China as one of the human rights national education and training bases. This shows the full affirmation and trust in the university＇s education, research and training work and also represents encouragement for its future work.展开更多
The durability and reliability of slab track structures are essential for the long-term safety and stable operation of high-speed railways.In order to provide a solid theoretical basis and technical reference for the ...The durability and reliability of slab track structures are essential for the long-term safety and stable operation of high-speed railways.In order to provide a solid theoretical basis and technical reference for the advancement of high-speed railway quality,this paper comprehensively discusses design theories of slab track structures,service performance evolution and maintenance technologies,and reviews the innovation happening in the industry.On top of that,the damage evolution,fatigue features and durability of slab tracks,which are highly relevant to serviceability,are summarized,and the future research trend of slab track service behaviours is pointed out.In addition,this paper summarizes the rules of establishing standards for damage maintenance,typical solutions for repairing damage and methods of evaluating the maintenance outcomes that combine field tests and numerical simulations.It also envisions a future direction where advanced testing technologies would assist the evaluation of maintenance effects.展开更多
When fuel efficiency is at stake,along with the reduction of the environmental foot print of air pollution,a need is presented to estimate a ship’s fuel consumption for a forthcoming voyage,and means for decision mak...When fuel efficiency is at stake,along with the reduction of the environmental foot print of air pollution,a need is presented to estimate a ship’s fuel consumption for a forthcoming voyage,and means for decision making and for cost saving.This paper suggests an operational approach for obtaining an accurate fuel consumption and speed curve,on the basis of major factors affecting it,namely,ship’s draft and displacement,weather force and direction,hull and propeller roughness.A statistical analysis on 418 noon reports of a Pure Car and Truck Carrier case ship is carried out and the influence of the above factors is calculated.As expected,stronger wind and head weather increases the fuel consumption,and the difference between several weather conditions could be quantified.A simple and accurate algorithm is proposed in order for ship owners,managers and operators to be in a position to apply the suggested method on their fleet.Finally,applications of the structured algorithm are introduced with examples,in estimating the fuel consumption of the case ship for a future voyage,and also the same for a sister ship.Furthermore,voyage planning in several scenarios is proposed in order to assist the stakeholders with decision making aimed to fuel saving and environmental friendliness of their ships.展开更多
基金Project supported by the National Key Research and Development Program of China(2021YFB3501002)the National Science and Technology Major Project(J2019-Ⅷ-0003-0165)+1 种基金the National Natural Science Foundation of China(52301059)the Shanghai Post-doctoral Excellence Program(2023372)。
文摘The flammability of magnesium alloys continues to be a significant barrier to their extensive application,and alloying with rare earth elements(REs)is an effective way to enhance the ignition and fire resistance of Mg alloys.Three commercial as-extruded Mg alloys(AZ80 and two Mg-RE alloys:EZ30K and WE43)were directly exposed to flame heating for revealing the evolutions of microstructure and mechanical properties,which is valuable in assessing the post-fire residual service performance of Mg alloy components.Results show that secondary phase dissolution,grain growth,grain boundary melting,alloy melting,and defects generation successively occur during the heating process.After short-term heating for 30 s,the elongation of AZ80 alloy increases significantly by 214%,from 3.82%to 12.01%,with minimal change in strength compared to the initial unheated state.This transformation is attributed to the recovery,grain growth,Mg17Al12 dissolution and dislocation density reduction.Conversely,EZ30K and WE43 alloys exhibit minimal changes in mechanical properties after short-term heating for 60 s,attributed to the pinning effect of REs.However,in subsequent heating states,resolidified microstructure and the presence of defects lead to a noteworthy decrease in both strength and elongation.Among these three alloys,the fire resistance follows this ranking:EZ30K>WE43>AZ80,primarily due to the high thermal conductivity of EZ30K alloy and the thermal stability improved by the addition of REs.
基金Xi'an Science and Technology Plan Project(23GXFW0055)Shaanxi Provincial Natural Science Basic Research Program Project(2024JC-YBQN-0525)National Natural Science Foundation of China(52001251)。
文摘TiN coatings were prepared by the novel dual-stage high power impulse magnetron sputtering(HIPIMS)technique under different deposition time conditions,and the effects of microstructure and stress state at different coating growth stages on the mechanical,tribological,and corrosion resistance performance of the coatings were analyzed.Results show that with the prolongation of deposition time from 30 min to 120 min,the surface structure of TiN coating exhibits a round cell structure with tightly doped small and large particles,maintaining the atomic stacking thickening mechanism of deposition-crystallization-growth.When the deposition time increases from 90 min to 120 min,the coating thickness increases from 3884 nm to 4456 nm,and the stress state of coating undergoes the compression-tension transition.When the deposition time is 90 min,TiN coating structure is dense and suffers relatively small compressive stress of−0.54 GPa.The coating has high hardness and elastic modulus,which are 27.5 and 340.2 GPa,respectively.Meanwhile,good tribological properties(average friction coefficient of 0.52,minimum wear rate of 1.68×10^(−4)g/s)and fine corrosion resistance properties(minimum corrosion current density of 1.0632×10^(−8)A·cm^(−2),minimum corrosion rate of 5.5226×10^(−5)mm·A^(−1))can also be obtained for the coatings.
文摘In the aerospace field, residual stress directly affects the strength, fatigue life and dimensional stability of thin-walled structural components, and is a key factor to ensure flight safety and reliability. At present, research on residual stress at home and abroad mainly focuses on the optimization of traditional detection technology, stress control of manufacturing process and service performance evaluation, among which research on residual stress detection methods mainly focuses on the improvement of the accuracy, sensitivity, reliability and other performance of existing detection methods, but it still faces many challenges such as extremely small detection range, low efficiency, large error and limited application range.
基金supported in part by the Graduate Research Innovation Project of Chongqing under grant CYB23237in part by the Doctoral Candidate Innovative Talent Program of CQUPT under grant BYJS202201+3 种基金in part by the National Natural Science Foundation of China(62271096,U20A20157)in part by the Natural Science Foundation of Chongqing,China(cstc2020jcyjzdxmX0024)in part by the University Innovation Research Group of Chongqing(CXQT20017)in part by the Youth Innovation Group Support Program of ICE Discipline of CQUPT(SCIE-QN-2022-04).
文摘In the upcoming B5G/6G era,Virtual Reality(VR)over wireless has become a typical application,which is an inevitable trend in the development of video.However,in immersive and interactive VR experiences,VR services typically exhibit high delay,while simultaneously posing challenges for the energy consumption of local devices.To address these issues,this paper aims to improve the performance of VR service in the edge-terminal cooperative system.Specifically,we formulate a joint Caching,Computing,and Communication(3C)VR service policy problem by optimizing the weighted sum of the total VR delivery delay and the energy consumption of local devices.To design the optimal VR service policy,the optimization problem is decoupled into three independent subproblems to be solved separately.To improve the caching efficiency within the network,a Bert-based user interest analysis method is first proposed to accurately characterize the content request behavior.Based on this,a service cost minimum-maximization problem is formulated under the consideration of performance fairness among users.Then,the joint caching and computing scheme is derived for each user with a given allocation of communication resources while a bisection-based communication scheme is acquired with the given information on the joint caching and computing policy.With alternative optimization,an optimal policy for joint 3C based on user interest can be finally obtained.Simulation results are presented to demonstrate the superiority of the proposed user interest-aware caching scheme and the effectiveness of the joint 3C optimization policy while considering user fairness.Our code is available at https://github.com/mrfuqaq1108/Interest-Aware-Joint-3C-Optimization.
基金support from the National Natural Science Foundation of China(Grant Nos.52072274,52272021,U23A20559 and 52232002)the Open Foundation of State Key Laboratory of Advanced Refractories(No.SKLAR202207)+1 种基金the Key Laboratory of Hubei Province for Coal Conversion and New Carbon Materials(Wuhan University of Science and Technology,WKDM202201)the Open/Innovation Foundation of Hubei Three Gorges Laboratory(SK232006).
文摘h-BN rods modified low-carbon alumina-carbon(Al_(2)O_(3)-C)refractories were prepared,and the effect of h-BN rod addition on the high-temperature properties was investigated and compared with commercial h-BN flake,carbon black,and carbon nanotubes additives.The results demonstrated that Al_(2)O_(3)-C refractories containing h-BN rods exhibited optimal high-temperature service performances,including 25%higher hot modulus of rupture,21.3%higher thermal shock strength residual ratio,20.9%lower in oxidation and 44.3%less in slag corrosion,compared to the counterpart specimens without additives.Moreover,benefiting from the synergistic enhancement of the rod-like h-BN and in-situ generated SiC whiskers,the high-temperature service performances of h-BN rods containing specimens outperformed counterpart specimens containing commercial h-BN flake,carbon black,and carbon nanotubes,respectively.
基金Project supported by the Key Research and Development Program of Shandong Province (2019JZZY010321)the Major Project of "Science and Technology Innovation 2025" in Ningbo City (2020Z050)+1 种基金Ningbo Natural Science Foundation (202003N4352)the Kunpeng Project in Zhejiang Province and National Natural Science Foundation of China (52101238)。
文摘We successfully fabricated partial Y substituted NdY-Fe-B magnets with nominal compositions of(Nd_(1-x)Y_(x))_(13.80)Fe_(ba1)Al_(0.24)Cu_(0.1)B_(6.04)(at%,x=0,0.1,0.2,0.3,0.4) by powder metallurgy process and the magnetic properties as well as service performances of the magnets were also systematically investigated.The phase constituents of the magnets have no obvious variation within the whole range of Y content,while the main phase grains form in-situ core-shell structure where Y gathers in the core and Nd mainly distributes in the shell.Compared with pure Nd-Fe-B magnets,the magnetic performances of Y substituted magnets slightly decrease on account of the poor intrinsic magnetic properties of Y_(2)Fe_(14)B.Fortunately,the μ_(O)M_(r),μ_(O)H_(cj) and(BH)_(max) of the 20 at% Y magnet still remain at a high level of 1.325 kG,1.173 kOe and 342.884 kj/m^(3),which approaches the performances of commercial N45-grade magnet.The service performances of Y substituted magnets indicate that though the surface corrosion products and Vickers hardness of the NdY-Fe-B magnets increase to a certain extent compared to Nd-Fe-B,the magnets with Y substitution still display relatively good service performances.Therefore,on the basis of sacrificing little partial magnetic and service performances,Y substituted Nd can still prepare NdY-Fe-B medium-grade magnets.By this way,we achieve the balanced utilization of rare earth resources,which has significant meanings for the industry and scientific research.
基金supported by The National Key Research and Development Program of China(No.2020YFB1708200).
文摘Design change is an inevitable part of the product development process.This study proposes an improved binary multi‐objective PSO algorithm guided by problem char-acteristics(P‐BMOPSO)to solve the optimisation problem of complex product change plan considering service performance.Firstly,a complex product multi‐layer network with service performance is established for the first time to reveal the impact of change effect propagation on the product service performance.Secondly,the concept of service performance impact(SPI)is defined by decoupling the impact of strongly associated nodes on the service performance in the process of change affect propagation.Then,a triple‐objective selection model of change nodes is established,which includes the three indicators:SPI degree,change cost,and change time.Furthermore,an integer multi‐objective particle swarm optimisation algorithm guided by problem characteristics is developed to solve the model above.Experimental results on the design change problem of a certain type of Skyworth TV verify the effectiveness of the established optimisation model and the proposed P‐BMOPSO algorithm.
基金This paper is supported by the National Natural Science Foundation of China (Grant No. 90304006),the Spe-cialized Research Fund for the Doctoral Program of Higher Education (SRFDP)(Grant No. 20020698018).
文摘An architecture for online discovery quantitative models system of service performance management is proposed. The system is capable of constructing the quantitative models without prior knowledge of the managed elements. The model can be updated continuously in response to the changes made in provider configurations and the evolution of business demands. Due to the existence of strong correlation between the distributed service metrics and response times, linear and hyper-linear quantitative models are constructed, which respectively, use stepwise multiple linear regression algorithm. The simulation results show the effectiveness of a quantitative model constructing system and model constructing algorithms.
基金the project supported by the Natural Science Foundation of Hubei Province(Grant No.2023BAB106)the National Natural Science Foundation of China(Grant No.U20A20239).
文摘The rapid development of iron and steel metallurgy technology has promoted the continuous innovation and iteration of carbon-containing refractories for clean steel smelting.To meet the high-quality requirements for clean steel production and full exploit the performance advantages of carbon-containing refractories in dynamic smelting environment,it is necessary to explore the role of graphite and modified graphite in carbon-containing refractories.Based on this,graphite surface modification methods,including surfactants,surface oxidation,and surface coating,and their applications in carbon-containing refractories are reviewed.The advantages and disadvantages of each method are analyzed for practical use.Furthermore,combined with the existing problems,the application prospect of improved graphite in carbon-containing refractories is discussed.
基金supported by National Key R&D Program of China(2021YFB2601200)the National Natural Science Foundation of China(52208412)+2 种基金Young Elite Scientists Sponsorship Program by CAST(2023QNRC001)Research Project of Beijing Municipal Commission of Education(KM202210016009)BUCEA Post Graduate Innovation Project,the Project of Construction and Support for High-Level Innovative Teams of Beijing Municipal Institutions(BPHR20220109).
文摘Asphalt pavement is the main type of pavement structure in China,and it accounts for more than 90%of the large-scale road network.As the service life of asphalt pavement increases,the demand for maintenance is increasing significantly.Accurately revealing the degradation mechanism and predicting the performance of asphalt pavement is the basis for the scientific maintenance decisions.Meanwhile,it is also beneficial for road construction planning and resource allocation.Based on numerous current studies,this review firstly provides a comprehensive summary of the internal factors such as structure and material,as well as external factors such as environment,load,and construction,that impact the performance of asphalt pavement.Simultaneously,the degradation trend of asphalt pavement performance under intricate conditions is also clarified.Furthermore,the commonly used performance prediction models of asphalt pavement are analyzed,such as deterministic methods,uncertainty methods,machine learning,dynamic methods and so on.And their applicability and limitations are also summarized.Finally,considering the complexity of predicting asphalt pavement performance,this review identifies key challenges and future prospects in this area.This provides theoretical support for accurately predicting the performance degeneration of asphalt pavement,making scientific maintenance decisions,and promoting the durability improvement of asphalt pavement.
基金Project supported by the Key Research and Development Program of Shandong Province(2019JZZY010321)the Major Project of"Science and Technology Innovation 2025"in Ningbo City(2020Z050)+1 种基金Ningbo Natural Science Foundation(202003N4352)the Science and Technology Major Project of the Jiangbei District of Ningbo(202001A01)。
文摘Low cost and high abundance rare earth elements Y and Ce have attracted tremendous interests of the industrial and scientific societies for fabricating the highly cost-performance efficient rare earth permanent magnets.However,the effect of separate replacement of Nd by Y or Ce on the performances of NdFeB-type magnet under the same atomic ratio and preparation conditions is still unclear.In this work,we systematically investigated the magnetic properties,thermal stabilities and service performances of(Nd_(0.8)Y_(0.2))_(13.80)Fe_(bal)Al_(0.24)Cu_(0.1)B_(6.04)(atomic fraction,denoted as 20 Y)and(Nd_(0.8)Ce_(0.2))_(13.80)Fe_(bal)Al_(0.24)Cu_(0.1)B_(6.04)(atomic fraction,denoted as 20 Ce)magnets.The results demonstrate that theμ_(0)M_(r),μ_(0)H_(c)and(BH)_(max)of 20 Y magnet are respectively 1.325 T,1.173 T and 343.467 kJ/m^(3),which are comprehensively higher than those of 20 Ce magnet(μ_(0)M_(r)=1.310 T,μ_(0)H_(c)=0.948 T,(BH)_(max)=321.105 kJ/m^(3)).Moreover,the 20 Y magnet has higher thermal stability compared with 20 Ce magnet which is favorable for the magnetic performances at elevated temperatures.The investigation of micro structure and elemental distribution indicates that the excellent magnetic performance s of NdY-Fe-B magnet can be attributed not only to the preferable intrinsic properties4πM_(s),H_(s)and T_(c)of Y_(2)Fe_(14)B,but also to the in-situ co re-shell structure of the 2:14:1 matrix phase grain with Yrich core and Nd-rich shell,along with the thicker grain boundary layer between the adjacent matrix phase grains in NdY-Fe-B magnet.Furthermore,the 20 Y magnet exhibits better mechanical property and higher corrosion resistance than 20 Ce magnet,which are helpful for prolonging the service life of the magnet in practical application.
基金This work was funded in part by the National Key Research and Development Program of China(Grant No.2017YFE0132100)Tsinghua-Toyota Joint Research Institute Cross-discipline Program,and the BNRist Program(Grant No.BNR2020TD01009).
文摘This paper focuses on solving the modeling issues of monitoring system service performance based on the network calculus theory.First,we formulate the service model of the smart grid monitoring system.Then,we derive the flow arrival curve based on the incremental process related functions.Next,we develop flow arrival curves for the case of the incremental process being a fractional Gaussian process,and then we obtain the generalized Cauchy process.Three technical theorems related to network calculus are presented as our main results.Mathematically,the variance of arrival flow for the continuous time case is derived.Assuming that the incremental process of network flow is a Gaussian stationary process,and given the auto-correlation function of the incremental process with violation probability,the formula of the arrival curve is derived.In addition,the overall flow variance under the discrete time case is explicitly derived.The theoretical results are evaluated in smart grid applications.Simulations indicate that the generalized Cauchy process outperforms the fractional Gaussian process for our considered problem.
基金Funded by the Natural Science Foundation of China(Nos.51378501,51174291,51109121,51278495,51008312)the Key Technological Research and Development Programs of Ministry of Railways,China(No.2008G031-18)
文摘In order to quantitatively describe the local corrosion process of steel bars in cracked concrete area, a new two-staged utility model is established, and the effect of transverse cracks on the reinforcement corrosion is analyzed from the angle of long-term service performance evaluation for reinforced concrete structure. Moreover, based on the principle of spectral analysis for environmental action of concrete, an equivalent relationship is established between the corrosion rate in the natural environment and that under the standard temperature and relative humidity condition according to the principle of equivalent annual corrosion depth. Comparison between the inspection results from some references and the calculated values by the two- staged utility model validates the feasibility of the proposed model. The model was applied to Chinese Railway Track System （CRTS） Ⅱ ballastless track slab with transverse dummy joints, from which satisfactory results of corrosion degree of steel bars were obtained.
基金funded by the National Natural Science Foundation of China[51778136 and 41972299].
文摘Purpose–This study aims to investigate the service performances of a new full-section asphalt concrete waterproof sealing structure(FSACWSS)for the high-speed railway subgrade through on-site tracking,monitoring and post-construction investigation.Design/methodology/approach–Based on the working state of the waterproof sealing structure,the main functional characteristics were analyzed,and a kind of roller-compacted high elastic modulus asphalt concrete(HEMAC)was designed and evaluated by several groups of laboratory tests.It is applied to an engineering test section,and the long-term performance monitoring and subgrade dynamic performance testing system were installed to track and monitor working performances of the test section and the adjacent contrast section with fiber-reinforced concrete.Findings–Results show that both the dynamic performance of the track structure and the subgrade in the test section meet the requirements of the specification limits.The water content in the subgrade of the test section is maintained at 8–18%,which is less affected by the weather.However,the water content in the subgrade bed of the contrast section is 10–35%,which fluctuates significantly with the weather.The heat absorption effect of asphalt concrete in the test section makes the temperature of the subgrade at the shoulder larger than that in the contrastive section.The monitoring value of the subgrade vertical deformation in the test section is slightly larger than that in the contrastive section,but all of them meet the limit requirements.The asphalt concrete in the test section is in good contact with the base,and there are no diseases such as looseness or spalling.Only a number of cracks are found at the joints of the base plates.However,there are more longitudinal and lateral cracks in the contrastive section,which seriously affects the waterproof and sealing effects.Besides,the asphalt concrete is easier to repair,featuring good maintainability.Originality/value–This research can provide a basis for popularization and application of the asphalt concrete waterproof sealing structure in high-speed railways.
基金The authors appreciate the financial support from the National Natural Science Foundation of China(No.51878167)Qing Lan Project of Jiangsu Province。
文摘As an important part of steel bridge deck,the engineering quality and service condition of steel bridge deck pavement(SBDP)directly affects the capacity and operational efficiency of the bridge.This paper reviews the history of the development of SBDP in China over the past 20 years from the exploration stage,rapid development stage and prosperity stage.The development and application of SBDP at different stages are discussed in terms of materials,structure,design,performance evaluation,maintenance and rehabilitation,respectively.The advantages and disadvantages of different pavement materials and structures,and the application of different research methods are summarized.The review shows that the improvement of pavement materials and structures and the development of new materials should be further studied on the multi-scale to enhance the durability of pavement materials,so as to extend the service life of pavements.The design method of SBDP related to the synergistic effect of vehicle,pavement and bridge should be established,and the design concept and method standard of rigid base pavement structure should be improved and formulate a complete design standard.In addition,multi-disease intelligent identification system and equipment should be studied to track the entire course of disease development in real time.And it is necessary to develop appropriate algorithms to select and classify the complex data of disease and maintenance history.
文摘With the growing environmental concerns, green supply chain management （GSCM） is gaining significant attention in the construction industry. Tracking and monitoring the environmental effects brought forth by the participating members along a supply chain is important to GSCM. The GreenSCOR model developed by the Supply Chain Council provides a generic framework for measuring the total carbon footprint and environmental footprint in a supply chain. The model is based on the Supply Chain Operations Reference （SCOR） model, which represents a supply chain network in a hierarchically structured manner. This paper describes the GreenSCOR framework and its potential application to the construction industry. This paper also presents a web services approach to incorporate the GreenSCOR model to the implementation of collaborative information systems. Each process element in the SCOR model is represented and delivered as individual web service units, which can be reused and integrated using standard web services technologies. The service units are combined and managed in a prototype web service collaborative framework, called SC Collaborator, which is designed and developed for supporting construction supply chain management. An illustrative example is presented to demonstrate the implementation of the GreenSCOR-based SC Collaborator framework.
文摘The Ministry of Education and the State Council Information Office have named Renmin University of China as one of the human rights national education and training bases. This shows the full affirmation and trust in the university＇s education, research and training work and also represents encouragement for its future work.
基金support from the National Natural Science Foundation of China (Grant no.52022085).
文摘The durability and reliability of slab track structures are essential for the long-term safety and stable operation of high-speed railways.In order to provide a solid theoretical basis and technical reference for the advancement of high-speed railway quality,this paper comprehensively discusses design theories of slab track structures,service performance evolution and maintenance technologies,and reviews the innovation happening in the industry.On top of that,the damage evolution,fatigue features and durability of slab tracks,which are highly relevant to serviceability,are summarized,and the future research trend of slab track service behaviours is pointed out.In addition,this paper summarizes the rules of establishing standards for damage maintenance,typical solutions for repairing damage and methods of evaluating the maintenance outcomes that combine field tests and numerical simulations.It also envisions a future direction where advanced testing technologies would assist the evaluation of maintenance effects.
文摘When fuel efficiency is at stake,along with the reduction of the environmental foot print of air pollution,a need is presented to estimate a ship’s fuel consumption for a forthcoming voyage,and means for decision making and for cost saving.This paper suggests an operational approach for obtaining an accurate fuel consumption and speed curve,on the basis of major factors affecting it,namely,ship’s draft and displacement,weather force and direction,hull and propeller roughness.A statistical analysis on 418 noon reports of a Pure Car and Truck Carrier case ship is carried out and the influence of the above factors is calculated.As expected,stronger wind and head weather increases the fuel consumption,and the difference between several weather conditions could be quantified.A simple and accurate algorithm is proposed in order for ship owners,managers and operators to be in a position to apply the suggested method on their fleet.Finally,applications of the structured algorithm are introduced with examples,in estimating the fuel consumption of the case ship for a future voyage,and also the same for a sister ship.Furthermore,voyage planning in several scenarios is proposed in order to assist the stakeholders with decision making aimed to fuel saving and environmental friendliness of their ships.
