Vehicle load is among the main factors affecting the deformation of subgrade soil.In this research study,the concept of impact type traffic load is introduced to investigate the effects of vehicle load based on the dy...Vehicle load is among the main factors affecting the deformation of subgrade soil.In this research study,the concept of impact type traffic load is introduced to investigate the effects of vehicle load based on the dynamic stress and displacement time histories acquired from seasonal frozen subgrade soils.Using freezing-thawing and dynamic triaxial tests and considering the amplitude and loading sequence of impact type traffic load,the residual deformation characteristics of subgrade soil under impact type traffic loads and freezing-thawing cycles is studied.It was found that under impact type traffic load,the residual deformation of soils increased sharply as the amplitude of impact type traffic load increased.It was also found that the increase in the amplitude of impact type traffic load led to the increase of residual deformation in a scale of power and exponential function.The amplitudes of impact type traffic load affect the development stress-strain path of the residual strain.After the soil experienced the proper amount of pre-vibration of the light load,residual deformation decreased by 15%.After freezing-thawing,the residual strain of soil increased as the amplitude of the impact type traffic loads increased.Also,when the amplification effect of freezing-thawing on the residual strain was basically stable,the residual deformation increased by about 10%.The peak impact type traffic load had a large effect on soil deformation after the freezing-thawing process,leading to the observation that of the earlier the peaks,the stronger the effect of freezing-thawing.After the soil was subjected to preloading with a small load,the influence of the freezing-thawing cycles gradually stabilized.The results may be useful in preventing and controlling the risk of subgrade soil failure when construction takes place spring thaw periods.展开更多
Energy-efficient data gathering in multi-hop wireless sensor networks was studied,considering that different node produces different amounts of data in realistic environments.A novel dominating set based clustering pr...Energy-efficient data gathering in multi-hop wireless sensor networks was studied,considering that different node produces different amounts of data in realistic environments.A novel dominating set based clustering protocol (DSCP) was proposed to solve the data gathering problem in this scenario.In DSCP,a node evaluates the potential lifetime of the network (from its local point of view) assuming that it acts as the cluster head,and claims to be a tentative cluster head if it maximizes the potential lifetime.When evaluating the potential lifetime of the network,a node considers not only its remaining energy,but also other factors including its traffic load,the number of its neighbors,and the traffic loads of its neighbors.A tentative cluster head becomes a final cluster head with a probability inversely proportional to the number of tentative cluster heads that cover its neighbors.The protocol can terminate in O(n/lg n) steps,and its total message complexity is O(n2/lg n).Simulation results show that DSCP can effectively prolong the lifetime of the network in multi-hop networks with unbalanced traffic load.Compared with EECT,the network lifetime is prolonged by 56.6% in average.展开更多
Industrial production of chemical cement leads to extreme emissions of greenhouse gases.Biological or bioinspired sustainable materials for soil treatment projects can be employed instead of chemical cement to heal th...Industrial production of chemical cement leads to extreme emissions of greenhouse gases.Biological or bioinspired sustainable materials for soil treatment projects can be employed instead of chemical cement to heal the carbon cycle in the ecosystem.The enzyme-induced calcite precipitation(EICP)method is one of the novel bio-inspired technologies that can be employed in soil treatment projects to increase desired properties of soils.While the monotonic and cyclic behavior of the enzymatically treated sands has been investigated comprehensively,the strain accumulation pattern in these improved soils under cyclic traffic loads has not been evaluated yet.In this paper,confined and unconfined cyclic compression tests are applied to the enzymatically lightly cemented sands,and the effects of the different parameters on their strain accumulation pattern are investigated for the first time in the literature.This study uses two types of specimens with unconfined compression strengths(UCS)equal to 42 kPa and 266 kPa.It is shown that the treated specimens have a rate-dependent behavior where cyclic loads with low frequencies lead to more resilient and plastic strains in the specimens.The results show that by approaching the maximum applied stresses to the UCS of the specimens(by breaking more calcite bonds between sand particles),the rate dependency behavior of specimens will reduce.Investigation of the effects of the cementation level demonstrated that by increasing the amount of the precipitated calcite from 0.38%to 0.83%,accumulated plastic strains are reduced almost 95%under the same loading condition.Effects of the initial static loads,confining pressures,the number of cycles,and amplitudes of the cyclic loads are also evaluated.展开更多
Designers search for N-nodes peer-to-peer networks that can have O （1） out-degree with O （log2 N） average distance. Peer-to-peer schemes based on de Bruijn graphs are found to meet this requirement. By defining av...Designers search for N-nodes peer-to-peer networks that can have O （1） out-degree with O （log2 N） average distance. Peer-to-peer schemes based on de Bruijn graphs are found to meet this requirement. By defining average load to evaluate the traffic load in a network, we show that in order to decrease the average load, the average distance of a network should decrease while the out-degree should increase. Especially, given out-degree k and N nodes, peer-to-peer schemes based on de Bruijn graphs have lower average load than other existing systems. The out-degree k of de Bruijn graphs should not be O（1） but should satisfy a lower bound described by an inequality κ^κ≥N^2, to ensure that the average load in peer-to-peer schemes based on de Bruijn graphs will not exceed that in Chord system.展开更多
This paper explores the challenges of controlling complex metro systems,which are influenced by uncertain and uncontrollable large passenger flow impacts.Traditionally,flow-limiting measures during peak periods have b...This paper explores the challenges of controlling complex metro systems,which are influenced by uncertain and uncontrollable large passenger flow impacts.Traditionally,flow-limiting measures during peak periods have been based on experience rather than scientific theory.To bridge this gap,we introduce a novel network analysis method inspired by control centrality theory.This approach assesses the impact of traffic loads from single or multiple sources on any node within the metro network.Our method provides a scientific basis for operators to develop policies for managing overloaded traffic,enhancing both safety and efficiency in metro system operations.展开更多
Geotechnical centrifuge tests were conducted to examine the influence of invert voids and surface traffic loads on 1400 mm diameter reinforced concrete pipes buried with a shallow soil cover depth of 700 mm.Void forma...Geotechnical centrifuge tests were conducted to examine the influence of invert voids and surface traffic loads on 1400 mm diameter reinforced concrete pipes buried with a shallow soil cover depth of 700 mm.Void formation beneath the pipe was simulated during centrifuge testing.The test results revealed that before void formation,the surface load directly above the middle of the pipe caused a significant increase in not only the circumferential bending moments but also the longitudinal bending moments,the latter of which was considerable and could not be ignored.Void formation beneath the middle of the pipe led to a reduction in both the circumferential bending moments and longitudinal bending moments at all measuring positions,i.e.,crown,springline,and invert.The most significant reduction occurred at the invert,and there was even a reversal in the sign of the invert longitudinal bending moment.A comparison was made between centrifuge tests with erosion voids and surface loads at different horizontal positions,which had a marked influence even when the positions differed by half a pipe length.Joint rotation played an important role in relieving large bending moments of pipe barrels in a jointed pipeline when the void and surface load were located at the joint.展开更多
Accurate assessment of the impact of heavy traffic loads on asphalt pavements requires a computational model which is able to calculate the response of the pavement fast and precisely. Currently the most finite elemen...Accurate assessment of the impact of heavy traffic loads on asphalt pavements requires a computational model which is able to calculate the response of the pavement fast and precisely. Currently the most finite element analysis programs based on traditional methods have various limitations. A specific program SAFEM was developed based on a semi-analytical finite element method to overcome the problems. It is a three-dimensional FE program that requires only a two-dimensional mesh by incorporating the semi- analytical method using Fourier series in the third dimension. The computational accuracy and efficiency of the program was verified by analytical verification previously. The experimental verification is carried out in this paper and the results show that the SAFEM is able to predict the mechanical responses of the asphalt pavement. Using the program SAFEM, the impact of heavy traffic loads was analyzed in terms of stress and strain dis- tribution, surface deflection and fatigue life. The results indicate that if the asphalt pave- ment is subjected to the heavy traffic load more, the thicknesses and stiffness of the pavement structural layers should be increased adequately in order to support the surface deflection, The compressive stress in asphalt binder course is relatively large and increases more significantly compared with that in the other asphalt layers when the axle load becomes larger. With comparison of the predicted fatigue life, the increase of the axle load will lead to the destruction of the asphalt pavement extremely easily.展开更多
The seamless integration of intelligent Internet of Things devices with conventional wireless sensor networks has revolutionized data communication for different applications,such as remote health monitoring,industria...The seamless integration of intelligent Internet of Things devices with conventional wireless sensor networks has revolutionized data communication for different applications,such as remote health monitoring,industrial monitoring,transportation,and smart agriculture.Efficient and reliable data routing is one of the major challenges in the Internet of Things network due to the heterogeneity of nodes.This paper presents a traffic-aware,cluster-based,and energy-efficient routing protocol that employs traffic-aware and cluster-based techniques to improve the data delivery in such networks.The proposed protocol divides the network into clusters where optimal cluster heads are selected among super and normal nodes based on their residual energies.The protocol considers multi-criteria attributes,i.e.,energy,traffic load,and distance parameters to select the next hop for data delivery towards the base station.The performance of the proposed protocol is evaluated through the network simulator NS3.40.For different traffic rates,number of nodes,and different packet sizes,the proposed protocol outperformed LoRaWAN in terms of end-to-end packet delivery ratio,energy consumption,end-to-end delay,and network lifetime.For 100 nodes,the proposed protocol achieved a 13%improvement in packet delivery ratio,10 ms improvement in delay,and 10 mJ improvement in average energy consumption over LoRaWAN.展开更多
Pavement damage increases rapidly with vehicle loads.The deterioration in pavements over time is caused by various factors but traffic loading plays a significant role in the consumption of pavement life.heavy vehicle...Pavement damage increases rapidly with vehicle loads.The deterioration in pavements over time is caused by various factors but traffic loading plays a significant role in the consumption of pavement life.heavy vehicle loads,in addition to the insufficient structural capacity of pavements,are a major contributor to poor road conditions.Alligator cracking,rutting,and roughness are among the various types of distresses that are performance measures of road conditions and are the primary focus of this study.Thus,in order to improve the understanding of pavement deterioration in terms of these distresses,this paper assesses the effect of different structural factors,traffic loading and environmental conditions on pavement performance.In this study,the base type,hot mix asphalt concrete(HMAC)layer thickness,base layer thickness,traffic loading,age,and environmental conditions(precipitation and temperature)are chosen as major contributing factors for the analysis of pavement performance.Generalized linear models(GLM),binary logistic regression(BLR),and random forest(RF)approaches are employed to evaluate the data from the Long-Term Pavement Performance Program(LTPP).Cross validation technique is used to compare the efficacy of regression models(GLM,BLR)with RF.Numerous performance indicators demonstrated that RF surpasses other models in terms of accuracy and identification of influencing variables.The result from the study shows that the important design parameters that have considerable effects on rutting,roughness,and alligator cracking are the base thickness and base type.Traffic loading,pavement age and environmental factors(precipitation and temperature)are critical factors and have a significant impact on pavement performance.This study brings a new idea of using statistical methods to analyze the effects of structural factors and loading on flexible pavements.展开更多
In design phases, expansion joints are required to have movement capacity, bearing capacity for static and dynamic loading, watertight, low noise emission and traffic safety. On the basis of the fact that failure due ...In design phases, expansion joints are required to have movement capacity, bearing capacity for static and dynamic loading, watertight, low noise emission and traffic safety. On the basis of the fact that failure due to dynamic loading is the main reason for the observed damages, attention is focused on the bearing capacity for dynamic loading governed by impact, because it differs from the static loading. In this study, from the viewpoint of durability, experimental studies for dynamic behavior were conducted for aluminium alloy expansion joints with perforated dowels. The validity of the perforated dowels against traffic impact loading was confirmed by both experimental and numerical studies.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
基金Fundamental Research Foundation for Universities of Heilongjiang Province under Grant No.2018-KYYWF-1651Natural Science Foundation of Heilongjiang Province under Grant Nos.ZD2019E009 and E2016045+1 种基金Scientific Research Fund of Institute of Engineering Mechanics,China Earthquake Administration under Grant Nos.2018D12 and 2019D16National Natural Science Foundation of China under Grant No.51378164。
文摘Vehicle load is among the main factors affecting the deformation of subgrade soil.In this research study,the concept of impact type traffic load is introduced to investigate the effects of vehicle load based on the dynamic stress and displacement time histories acquired from seasonal frozen subgrade soils.Using freezing-thawing and dynamic triaxial tests and considering the amplitude and loading sequence of impact type traffic load,the residual deformation characteristics of subgrade soil under impact type traffic loads and freezing-thawing cycles is studied.It was found that under impact type traffic load,the residual deformation of soils increased sharply as the amplitude of impact type traffic load increased.It was also found that the increase in the amplitude of impact type traffic load led to the increase of residual deformation in a scale of power and exponential function.The amplitudes of impact type traffic load affect the development stress-strain path of the residual strain.After the soil experienced the proper amount of pre-vibration of the light load,residual deformation decreased by 15%.After freezing-thawing,the residual strain of soil increased as the amplitude of the impact type traffic loads increased.Also,when the amplification effect of freezing-thawing on the residual strain was basically stable,the residual deformation increased by about 10%.The peak impact type traffic load had a large effect on soil deformation after the freezing-thawing process,leading to the observation that of the earlier the peaks,the stronger the effect of freezing-thawing.After the soil was subjected to preloading with a small load,the influence of the freezing-thawing cycles gradually stabilized.The results may be useful in preventing and controlling the risk of subgrade soil failure when construction takes place spring thaw periods.
基金Projects(61173169,61103203)supported by the National Natural Science Foundation of ChinaProject(NCET-10-0798)supported by the Program for New Century Excellent Talents in University of ChinaProject supported by the Post-doctoral Program and the Freedom Explore Program of Central South University,China
文摘Energy-efficient data gathering in multi-hop wireless sensor networks was studied,considering that different node produces different amounts of data in realistic environments.A novel dominating set based clustering protocol (DSCP) was proposed to solve the data gathering problem in this scenario.In DSCP,a node evaluates the potential lifetime of the network (from its local point of view) assuming that it acts as the cluster head,and claims to be a tentative cluster head if it maximizes the potential lifetime.When evaluating the potential lifetime of the network,a node considers not only its remaining energy,but also other factors including its traffic load,the number of its neighbors,and the traffic loads of its neighbors.A tentative cluster head becomes a final cluster head with a probability inversely proportional to the number of tentative cluster heads that cover its neighbors.The protocol can terminate in O(n/lg n) steps,and its total message complexity is O(n2/lg n).Simulation results show that DSCP can effectively prolong the lifetime of the network in multi-hop networks with unbalanced traffic load.Compared with EECT,the network lifetime is prolonged by 56.6% in average.
文摘Industrial production of chemical cement leads to extreme emissions of greenhouse gases.Biological or bioinspired sustainable materials for soil treatment projects can be employed instead of chemical cement to heal the carbon cycle in the ecosystem.The enzyme-induced calcite precipitation(EICP)method is one of the novel bio-inspired technologies that can be employed in soil treatment projects to increase desired properties of soils.While the monotonic and cyclic behavior of the enzymatically treated sands has been investigated comprehensively,the strain accumulation pattern in these improved soils under cyclic traffic loads has not been evaluated yet.In this paper,confined and unconfined cyclic compression tests are applied to the enzymatically lightly cemented sands,and the effects of the different parameters on their strain accumulation pattern are investigated for the first time in the literature.This study uses two types of specimens with unconfined compression strengths(UCS)equal to 42 kPa and 266 kPa.It is shown that the treated specimens have a rate-dependent behavior where cyclic loads with low frequencies lead to more resilient and plastic strains in the specimens.The results show that by approaching the maximum applied stresses to the UCS of the specimens(by breaking more calcite bonds between sand particles),the rate dependency behavior of specimens will reduce.Investigation of the effects of the cementation level demonstrated that by increasing the amount of the precipitated calcite from 0.38%to 0.83%,accumulated plastic strains are reduced almost 95%under the same loading condition.Effects of the initial static loads,confining pressures,the number of cycles,and amplitudes of the cyclic loads are also evaluated.
文摘Designers search for N-nodes peer-to-peer networks that can have O （1） out-degree with O （log2 N） average distance. Peer-to-peer schemes based on de Bruijn graphs are found to meet this requirement. By defining average load to evaluate the traffic load in a network, we show that in order to decrease the average load, the average distance of a network should decrease while the out-degree should increase. Especially, given out-degree k and N nodes, peer-to-peer schemes based on de Bruijn graphs have lower average load than other existing systems. The out-degree k of de Bruijn graphs should not be O（1） but should satisfy a lower bound described by an inequality κ^κ≥N^2, to ensure that the average load in peer-to-peer schemes based on de Bruijn graphs will not exceed that in Chord system.
基金support for this paper by the National Key R&D Program of China(Grant No.2021YFC2600504)the National Natural Science Foundation of China(Grant No.72174104).
文摘This paper explores the challenges of controlling complex metro systems,which are influenced by uncertain and uncontrollable large passenger flow impacts.Traditionally,flow-limiting measures during peak periods have been based on experience rather than scientific theory.To bridge this gap,we introduce a novel network analysis method inspired by control centrality theory.This approach assesses the impact of traffic loads from single or multiple sources on any node within the metro network.Our method provides a scientific basis for operators to develop policies for managing overloaded traffic,enhancing both safety and efficiency in metro system operations.
基金financial support received from the National Natural Science Foundation of China(Grant No.51978382).
文摘Geotechnical centrifuge tests were conducted to examine the influence of invert voids and surface traffic loads on 1400 mm diameter reinforced concrete pipes buried with a shallow soil cover depth of 700 mm.Void formation beneath the pipe was simulated during centrifuge testing.The test results revealed that before void formation,the surface load directly above the middle of the pipe caused a significant increase in not only the circumferential bending moments but also the longitudinal bending moments,the latter of which was considerable and could not be ignored.Void formation beneath the middle of the pipe led to a reduction in both the circumferential bending moments and longitudinal bending moments at all measuring positions,i.e.,crown,springline,and invert.The most significant reduction occurred at the invert,and there was even a reversal in the sign of the invert longitudinal bending moment.A comparison was made between centrifuge tests with erosion voids and surface loads at different horizontal positions,which had a marked influence even when the positions differed by half a pipe length.Joint rotation played an important role in relieving large bending moments of pipe barrels in a jointed pipeline when the void and surface load were located at the joint.
基金parts of the research projects carried out at the request of the Federal Ministry of Transport and Digital Infrastructure,requested by the Federal Highway Research Institute,under research projects No.04.0259/2012/NGB and FE 88.0137/FE88.0138parts of the research project carried out at the request of the German ResearchFoundation,under research projects No.FOR 2089
文摘Accurate assessment of the impact of heavy traffic loads on asphalt pavements requires a computational model which is able to calculate the response of the pavement fast and precisely. Currently the most finite element analysis programs based on traditional methods have various limitations. A specific program SAFEM was developed based on a semi-analytical finite element method to overcome the problems. It is a three-dimensional FE program that requires only a two-dimensional mesh by incorporating the semi- analytical method using Fourier series in the third dimension. The computational accuracy and efficiency of the program was verified by analytical verification previously. The experimental verification is carried out in this paper and the results show that the SAFEM is able to predict the mechanical responses of the asphalt pavement. Using the program SAFEM, the impact of heavy traffic loads was analyzed in terms of stress and strain dis- tribution, surface deflection and fatigue life. The results indicate that if the asphalt pave- ment is subjected to the heavy traffic load more, the thicknesses and stiffness of the pavement structural layers should be increased adequately in order to support the surface deflection, The compressive stress in asphalt binder course is relatively large and increases more significantly compared with that in the other asphalt layers when the axle load becomes larger. With comparison of the predicted fatigue life, the increase of the axle load will lead to the destruction of the asphalt pavement extremely easily.
基金This work was supported by the Basic Science Research Program through the NationalResearch Foundation ofKorea(NRF)funded by the Ministry of Education under Grant RS-2023-00237300 and Korea Institute of Planning and Evaluation for Technology in Food,Agriculture and Forestry(IPET)through the Agriculture and Food Convergence Technologies Program for Research Manpower Development,funded by Ministry of Agriculture,Food and Rural Affairs(MAFRA)(Project No.RS-2024-00397026).
文摘The seamless integration of intelligent Internet of Things devices with conventional wireless sensor networks has revolutionized data communication for different applications,such as remote health monitoring,industrial monitoring,transportation,and smart agriculture.Efficient and reliable data routing is one of the major challenges in the Internet of Things network due to the heterogeneity of nodes.This paper presents a traffic-aware,cluster-based,and energy-efficient routing protocol that employs traffic-aware and cluster-based techniques to improve the data delivery in such networks.The proposed protocol divides the network into clusters where optimal cluster heads are selected among super and normal nodes based on their residual energies.The protocol considers multi-criteria attributes,i.e.,energy,traffic load,and distance parameters to select the next hop for data delivery towards the base station.The performance of the proposed protocol is evaluated through the network simulator NS3.40.For different traffic rates,number of nodes,and different packet sizes,the proposed protocol outperformed LoRaWAN in terms of end-to-end packet delivery ratio,energy consumption,end-to-end delay,and network lifetime.For 100 nodes,the proposed protocol achieved a 13%improvement in packet delivery ratio,10 ms improvement in delay,and 10 mJ improvement in average energy consumption over LoRaWAN.
文摘Pavement damage increases rapidly with vehicle loads.The deterioration in pavements over time is caused by various factors but traffic loading plays a significant role in the consumption of pavement life.heavy vehicle loads,in addition to the insufficient structural capacity of pavements,are a major contributor to poor road conditions.Alligator cracking,rutting,and roughness are among the various types of distresses that are performance measures of road conditions and are the primary focus of this study.Thus,in order to improve the understanding of pavement deterioration in terms of these distresses,this paper assesses the effect of different structural factors,traffic loading and environmental conditions on pavement performance.In this study,the base type,hot mix asphalt concrete(HMAC)layer thickness,base layer thickness,traffic loading,age,and environmental conditions(precipitation and temperature)are chosen as major contributing factors for the analysis of pavement performance.Generalized linear models(GLM),binary logistic regression(BLR),and random forest(RF)approaches are employed to evaluate the data from the Long-Term Pavement Performance Program(LTPP).Cross validation technique is used to compare the efficacy of regression models(GLM,BLR)with RF.Numerous performance indicators demonstrated that RF surpasses other models in terms of accuracy and identification of influencing variables.The result from the study shows that the important design parameters that have considerable effects on rutting,roughness,and alligator cracking are the base thickness and base type.Traffic loading,pavement age and environmental factors(precipitation and temperature)are critical factors and have a significant impact on pavement performance.This study brings a new idea of using statistical methods to analyze the effects of structural factors and loading on flexible pavements.
文摘In design phases, expansion joints are required to have movement capacity, bearing capacity for static and dynamic loading, watertight, low noise emission and traffic safety. On the basis of the fact that failure due to dynamic loading is the main reason for the observed damages, attention is focused on the bearing capacity for dynamic loading governed by impact, because it differs from the static loading. In this study, from the viewpoint of durability, experimental studies for dynamic behavior were conducted for aluminium alloy expansion joints with perforated dowels. The validity of the perforated dowels against traffic impact loading was confirmed by both experimental and numerical studies.
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.
