Machine learning-assisted methods for rapid and accurate prediction of temperature field,mushy zone,and grain size were proposed for the heating−cooling combined mold(HCCM)horizontal continuous casting of C70250 alloy...Machine learning-assisted methods for rapid and accurate prediction of temperature field,mushy zone,and grain size were proposed for the heating−cooling combined mold(HCCM)horizontal continuous casting of C70250 alloy plates.First,finite element simulations of casting processes were carried out with various parameters to build a dataset.Subsequently,different machine learning algorithms were employed to achieve high precision in predicting temperature fields,mushy zone locations,mushy zone inclination angle,and billet grain size.Finally,the process parameters were quickly optimized using a strategy consisting of random generation,prediction,and screening,allowing the mushy zone to be controlled to the desired target.The optimized parameters are 1234℃for heating mold temperature,47 mm/min for casting speed,and 10 L/min for cooling water flow rate.The optimized mushy zone is located in the middle of the second heat insulation section and has an inclination angle of roughly 7°.展开更多
Facing increasing passenger and cargo transport demand and limited re-source in the 13th Five-Year period, how to make a breakthrough and substantial progress has become a key issue on planning and the Top-level Desig...Facing increasing passenger and cargo transport demand and limited re-source in the 13th Five-Year period, how to make a breakthrough and substantial progress has become a key issue on planning and the Top-level Design. In this paper we judged and analyzed the current development and potential demand of the energy saving and emission reduction in Beijing traffic industry. Through application of energy and emission prediction model which based on the vehicle activity data, the development goals of “one drop, double control, and triple upgrade” have been put forward. In order to achieve the goal, “5 + 1” development strategies should be implemented, and we also proposed the thinking and recommendations on sustainable development of transportation.展开更多
This paper investigated the interaction effects between inventory and transportation strategies in the logistics network. Demand volumes and shipping sizes were simulated as part of a new conceptual model using a disc...This paper investigated the interaction effects between inventory and transportation strategies in the logistics network. Demand volumes and shipping sizes were simulated as part of a new conceptual model using a discrete event simulation by minimizing the total logistics cost in the supply chain. The experiments indicate that the full truckload scenario leads to cost efficiency and the larger demand size results in smaller cost per unit based on economies of scale. Considering the interaction effects, demand size has a greater impact on cost reduction than shipping size. The total logistics cost in the system is dependent on replenishment rate and flow rates from the higher to the lower echelon. High inventory cost is the result of a fast replenishment rate and frequent orders, while shipping cost is dependent on the flow rates in a process and total travelling time or total travelling distance. Shipping size also has an impact on the level of service and the total cost along with effective order variability.展开更多
This study reviews productivity growth in the five major transportation industries in the United States (airline, truck, rail, pipeline, and water) and the pooled transportation industry from 2004 to 2011. We measure ...This study reviews productivity growth in the five major transportation industries in the United States (airline, truck, rail, pipeline, and water) and the pooled transportation industry from 2004 to 2011. We measure the average productivity for these eight years by state in each transportation industry and the annual average productivity by transportation industry. The major findings are that the U.S. transportation industry shows strong and positive productivity growth except that in the years of the global financial crisis in 2007, 2008, and 2010, and among the five transportation industries, the rail and water sectors show the highest productivity growth in 2011.展开更多
Determining earth pressure on jacked pipes is essential for ensuring lining safety and calculating jacking force,especially for deep-buried pipes.To better reflect the soil arching effect resulting from the excavation...Determining earth pressure on jacked pipes is essential for ensuring lining safety and calculating jacking force,especially for deep-buried pipes.To better reflect the soil arching effect resulting from the excavation of rectangular jacked pipes and the distribution of the earth pressure on jacked pipes,we present an analytical solution for predicting the vertical earth pressure on deep-buried rectangular pipe jacking tunnels,incorporating the tunnelling-induced ground loss distribution.Our proposed analytical model consists of the upper multi-layer parabolic soil arch and the lower friction arch.The key parameters(i.e.,width and height of friction arch B and height of parabolic soil arch H 1)are determined according to the existing research,and an analytical solution for K l is derived based on the distribution characteristics of the principal stress rotation angle.With consideration for the transition effect of the mechanical characteristics of the parabolic arch zone,an analytical solution for soil load transfer is derived.The prediction results of our analytical solution are compared with tests and simulation results to validate the effectiveness of the proposed analytical solution.Finally,the effects of different parameters on the soil pressure are discussed.展开更多
Loess slopes in cold and arid regions are susceptible to shallow soil degradation,which may trigger severe environmental problems related to soil erosion.To address this environmental challenge,this study selected a c...Loess slopes in cold and arid regions are susceptible to shallow soil degradation,which may trigger severe environmental problems related to soil erosion.To address this environmental challenge,this study selected a compound ecological curing agent composed of gellan gum and guar gum for stabilizing shallow loess slopes.Triaxial compression and disintegration tests were employed to comparatively analyze the effects of compound gum content,mass mix ratio,and curing age on the mechanical and disintegration properties of solidified loess.The curing mechanism was analyzed using scanning electron microscopy(SEM),and the ecological protection effect was monitored for a 60-day period.The results indicate that gellan gum,guar gum,and the compound gum can enhance the mechanical and disintegration properties of loess,promote plant growth,and optimize the ecological environment.However,the combination of gellan gum and guar gum proves more effective than using either gellan gum or guar gum alone.Considering the effects on mechanical properties,disintegration performance,and material economy,the disintegration rate of loess decreases by 75.72%compared to plain loess when the compound glue content is 0.5%,the mixing ratio of gellan gum to guar gum is 3:7 and the curing age is 7 days.Meanwhile,the cohesion and internal friction angle increase by 118.06%and 10.97%,respectively.Moreover,the disintegration performance and mechanical properties of the samples first increase and then decrease with the increase in compound glue and the mix ratio and are basically stabilized after the curing age reaches 7d.展开更多
Structural properties of the ship container logistics network of China(SCLNC)are studied in the light of recent investigations of complex networks.SCLNC is composed of a set of routes and ports located along the sea o...Structural properties of the ship container logistics network of China(SCLNC)are studied in the light of recent investigations of complex networks.SCLNC is composed of a set of routes and ports located along the sea or river.Network properties including the degree distribution,degree correlations,clustering,shortest path length,centrality and betweenness are studied in different definition of network topology.It is found that geographical constraint plays an important role in the network topology of SCLNC.We also study the traffic flow of SCLNC based on the weighted network representation,and demonstrate the weight distribution can be described by power law or exponential function depending on the assumed definition of network topology.Other features related to SCLNC are also investigated.展开更多
Digital Twin (DT) technology is revolutionizing the railway sector by providing a virtual replica of physical systems, enabling real-time monitoring, predictive maintenance, and enhanced decision-making. This systemat...Digital Twin (DT) technology is revolutionizing the railway sector by providing a virtual replica of physical systems, enabling real-time monitoring, predictive maintenance, and enhanced decision-making. This systematic literature review examines the status, enabling technologies, case studies, and frameworks for DT applications in railway systems with 91 selected papers from Scopus, Web of Science, IEEE, and the Snowballing Technique. The review focuses on four primary subsystems: tracks, civil structures, vehicles, and overhead contact line structures. Key findings reveal that DT has successfully optimized maintenance strategies, improved operational efficiency, and enhanced system safety. Internet of Things (IoT) devices, Artificial Intelligence (AI), machine learning, and cloud computing are critical in implementing DT models. However, challenges like data integration, high implementation costs, and cybersecurity risks remain, necessitating the discussed implications. Future research should focus on improving data interoperability, reducing costs through scalable cloud-based solutions, and addressing cybersecurity vulnerabilities. DT technology has the potential to revolutionize railway infrastructure management, ensuring greater efficiency, safety, and sustainability.展开更多
Integrating autonomous vehicles (AVs) and autonomous parking spaces (APS) marks a transformative development in urban mobility and sustainability. This paper reflects on these technologies’ historical evolution, curr...Integrating autonomous vehicles (AVs) and autonomous parking spaces (APS) marks a transformative development in urban mobility and sustainability. This paper reflects on these technologies’ historical evolution, current interdependence, and future potential through the lens of environmental, social, and economic sustainability. Historically, parking systems evolved from manual designs to automated processes yet remained focused on convenience rather than sustainability. Presently, advancements in smart infrastructure and vehicle-to-infrastructure (V2I) communication have enabled AVs and APS to operate as a cohesive system, optimizing space, energy, and transportation efficiency. Looking ahead, the seamless integration of AVs and APS into broader smart city ecosystems promises to redefine urban landscapes by repurposing traditional parking infrastructure into multifunctional spaces and supporting renewable energy initiatives. These technologies align with global sustainability goals by mitigating emissions, reducing urban sprawl, and fostering adaptive land uses. This reflection highlights the need for collaborative efforts among stakeholders to address regulatory and technological challenges, ensuring the equitable and efficient deployment of AVs and APS for smarter, greener cities.展开更多
Electrochemical impedance spectroscopy(EIS)was used to examine the electrical properties of metakaolin(MK)cement-based materials at elevated temperatures.We utilized a new equivalent circuit to investigate the EIS res...Electrochemical impedance spectroscopy(EIS)was used to examine the electrical properties of metakaolin(MK)cement-based materials at elevated temperatures.We utilized a new equivalent circuit to investigate the EIS results of cementitious materials blended with MK at these temperatures.A new evaluation method to high temperature damage is proposed.The findings show that both elevated temperatures and MK contents in cement mortar can impact the impedance spectra’s form properties.However,the residual compressive strength of the MK-blended cementitious material at elevated temperatures does not improve with the addition of MK.A quantitative relationship between the electrochemical parameters of the new equivalent circuit and the residual compressive strength is determined.The degree of high-temperature damage to cementitious materials can be evaluated based on these electrochemical parameters,providing a new approach for evaluating the high-temperature damage of MK-blend cementitious materials.展开更多
Solute atoms and precipitates significantly influence the mechanical properties of Mg alloys.Previous studies have mainly focused on the segregation behaviors of Mg alloys after annealing.In this study,we investigated...Solute atoms and precipitates significantly influence the mechanical properties of Mg alloys.Previous studies have mainly focused on the segregation behaviors of Mg alloys after annealing.In this study,we investigated the segregation behaviors of an Mg-RE alloy under deformation.We found that the enrichment of solute atoms occurred in{101^(-)1}compressive twin boundaries under compression at 298 K without any annealing in an Mg-RE alloy by scanning transmission electron microscopy and energy-dispersive X-ray analysis.The segregated solutes and precipitates impeded the twin growth,partially contributing to the formation of small-sized{101^(-)1}compressive twins.This research indicates the twin boundaries can be strengthened by segregated solutes and precipitates formed under deformation at room temperature.展开更多
This paper presents a method for fabricating a low-cost,highly reproducible miniature optical fiber Fabry-Perot(FP)sensor based on a polydimethylsiloxane(PDMS)end-cap structure.The FP cavity end-cap is formed by the o...This paper presents a method for fabricating a low-cost,highly reproducible miniature optical fiber Fabry-Perot(FP)sensor based on a polydimethylsiloxane(PDMS)end-cap structure.The FP cavity end-cap is formed by the optical fiber end-face and a PDMS droplet deposited onto it.The PDMS deposition is achieved by immersing the fiber end into pre-cured PDMS at a fixed speed,a process requiring careful control of PDMS viscosity and surface tension.By leveraging PDMS’s excellent thermal expansion coefficient,Poisson’s ratio,and other parameters,this method achieves high reproducibility via viscosity-optimized pre-curing,enhanced sensitivity for temperature measurements,and significant cost reduction versus commercial counterparts.Fiber FP sensors are increasingly widely used in biomedical and precision detection fields owing to their significant advantages,including small size,light weight,high sensitivity,and immunity to electromagnetic interference.In the fabrication of fiber FP sensors,using polymer materials is an effective technical approach.These polymers can be applied as coatings on the optical fiber end-face or as interlayer materials embedded between fibers to form the FP cavity structure,which not only significantly improves the overall sensor performance,but also enhances its sensitivity to changes in temperature,pressure,and refractive index.In the final part of this study,we successfully validated the exceptional performance of the PDMS end-cap based fiber FP sensor in detecting different temperatures conditions.Experimental results demonstrate a temperature sensitivity of 0.752 nm/℃for sensors with a 60-μm PDMS end-cap,further confirming the sensor’s reliability and efficiency in practical applications.展开更多
The quality of rebar welds directly impacts the overall service performance of highway infrastructure.However,current assessments of weld appearance quality primarily rely on traditional inspection methods such as man...The quality of rebar welds directly impacts the overall service performance of highway infrastructure.However,current assessments of weld appearance quality primarily rely on traditional inspection methods such as manual visual inspection,which suffer from significant limitations in accuracy,reliability,and efficiency.Given the increasing demand for safety performance inspections of highway infrastructure in China,traditional methods struggle to meet modern rapid inspection requirements.Therefore,this study proposes the design of a portable,non-destructive inspection device for rebar weld appearance,utilizing visible light vision and line-structured light 3D scanning technology.The device is equipped with an STM32 master control chip to manage encoder reading,scanning laser control,ring fill light,industrial camera synchronization,image acquisition,and serial port command transmission.Additionally,a weld image processing and detection software system was developed to receive,store,and identify weld defects.A field inspection prototype was created and subjected to various defect weld detection experiments in a laboratory setting.Experimental results demonstrate that the device can accurately measure weld parameters by acquiring multimodal images,fulfilling defect detection requirements.The device features high detection accuracy,portability,and user-friendliness,making it significant for the objective inspection and evaluation of rebar weld appearance and welding quality.展开更多
To propel the application of a bottom-hinged flap breakwater in real sea conditions,a two-dimensional computational fluid dynamics numerical model was conducted to investigate the pitching motion response and wave att...To propel the application of a bottom-hinged flap breakwater in real sea conditions,a two-dimensional computational fluid dynamics numerical model was conducted to investigate the pitching motion response and wave attenuation in random waves.First,the flow velocity distribution characteristic of the pitching flap at typical times was summarized.Then,the effects of random wave and flap parameters on the flap’s significant pitching angle amplitude θ_(s) and hydrodynamic coefficients were investigated.The results reveal that θ_(s) and wave reflection coefficient K_(r) values increase with increasing significant wave height Hs,random wave steepnessλs,and flap relative height.As Hs andλs increase,the wave transmission coefficient K_(t) increases while the wave dissipation coefficient K_(d) decreases.Additionally,K_(t) decreases with increasing flap relative height.With increasing equivalent damping coefficient ratio,θ_(s) and K_(t) decrease,while K_(r) and K_(d) increase.The relationships betweenλs and flap relative height on the one hand andθ_(s),K_(r),K_(t),and K_(d) in random waves on the other hand are compared to those in regular waves.Based on the equal incident wave energy and the equal incident wave energy flux,the pitching flap performs better in the wave attenuation capability under random waves than in regular waves.Finally,the dimensionless parameters with respect to random wave and flap were used to derive the K_(r) and K_(t) for-mulae,which were validated with the related data.展开更多
Custom 465(C465)is a martensitic stainless steel known for its high strength,toughness,and corrosion resistance,widely used in aerospace,automotive,and medical industries.However,limited work has been conducted on its...Custom 465(C465)is a martensitic stainless steel known for its high strength,toughness,and corrosion resistance,widely used in aerospace,automotive,and medical industries.However,limited work has been conducted on its additive manufacturing(AM)and no dedicated heat treatments have been developed for additively manufactured C465 to optimize its strength-ductility trade-off.In this work,the C465 was fabricated via laser powder bed fusion.The effect of hot isostatic pressing,solid solution,cryogenic treatment(−78.5℃),and aging on the composition homogenization,austenite-to-martensite transition,and Ni_(3)Ti precipitation were systemically investigated.The atom probe tomography analysis reveals that Mo atoms accumulate on Ni_(3)Ti precipitate surfaces and inhibits the Ni_(3)Ti growth,con-tributing to the enhanced strength of C465.The modified heat treatment for additively manufactured C465 reaches comparable tensile strength with the wrought counterpart,yielding an ultimate tensile strength of 1773 MPa,yield strength of 1686 MPa,and elongation of 6.5%.A yield strength calculation model was proposed and validated with measured strength under various heat treatments,providing valuable insight for heat treatment design towards diverse industrial applications.展开更多
Digital modeling and autonomous control of the die forging process are significant challenges in realizing high-quality intelli-gent forging of components.Using the die forging of AA2014 aluminum alloy as a case study...Digital modeling and autonomous control of the die forging process are significant challenges in realizing high-quality intelli-gent forging of components.Using the die forging of AA2014 aluminum alloy as a case study,a machine-learning-assisted method for di-gital modeling of the forging force and autonomous control in response to forging parameter disturbances was proposed.First,finite ele-ment simulations of the forging processes were conducted under varying friction factors,die temperatures,billet temperatures,and for-ging velocities,and the sample data,including process parameters and forging force under different forging strokes,were gathered.Pre-diction models for the forging force were established using the support vector regression algorithm.The prediction error of F_(f),that is,the forging force required to fill the die cavity fully,was as low as 4.1%.To further improve the prediction accuracy of the model for the ac-tual F_(f),two rounds of iterative forging experiments were conducted using the Bayesian optimization algorithm,and the prediction error of F_(f) in the forging experiments was reduced from 6.0%to 1.5%.Finally,the prediction model of F_(f) combined with a genetic algorithm was used to establish an autonomous optimization strategy for the forging velocity at each stage of the forging stroke,when the billet and die temperatures were disturbed,which realized the autonomous control in response to disturbances.In cases of−20 or−40℃ reductions in the die and billet temperatures,forging experiments conducted with the autonomous optimization strategy maintained the measured F_(f) around the target value of 180 t,with the relative error ranging from−1.3%to+3.1%.This work provides a reference for the study of di-gital modeling and autonomous optimization control of quality factors in the forging process.展开更多
Designing low-density,high-strength Mg-Li alloys is a major challenge in achieving extreme lightweighting of high-end equipment.This study proposes an interpretable machine learning strategy to simultaneously enhance ...Designing low-density,high-strength Mg-Li alloys is a major challenge in achieving extreme lightweighting of high-end equipment.This study proposes an interpretable machine learning strategy to simultaneously enhance the mechanical properties and corrosion resistance of Mg-Li alloy.Key alloy factors(KAFs)influencing ultimate tensile strength(UTS),elongation(EL),and corrosion rate(CR)were identified through alloy factor construction and screening.Using KAFs and processing parameters as inputs,gradient boosting regression models for UTS,EL,and CR were established,achieving the coefficients of determination of test-set above 0.85.Then,SHapley Additive exPlanations(SHAP)analysis quantified the impact of KAFs,and an element evaluation method was established to identify Al,Si,Ca,and Zn as candidates for alloy design.Finally,three new alloys were designed via multi-objective optimization.In the hot-extruded state,they exhibited UTS of 253∼273 MPa,EL of 18.4%∼27.9%,CR of 0.55∼1.61 mg/(cm^(2)·day),and ρ of 1.49∼1.54 g/cm^(3).Compared to LAZ103,the new alloys show 34%∼44%higher UTS,35%∼79%lower CR,and comparable ρ.Microstructural analysis revealed increasedα-Mg,decreasedβ-Li,reduced coarse secondary phases,and fine Ca-/Si-rich precipitates which are conducive to grain refinement and dislocation density increasing,synergistically enhancing comprehensive property.展开更多
Varied slope structures have different landslide initiation mechanisms.However,the role of interfacial asperities in controlling sliding initiation is unclear.This study develops a novel analytical method for interfac...Varied slope structures have different landslide initiation mechanisms.However,the role of interfacial asperities in controlling sliding initiation is unclear.This study develops a novel analytical method for interface mechanisms in practical landslide scenarios.Based on asperity theory,theoretical derivations were conducted,yielding an equilibrium equation grounded in the maximum shear length of asperities(Llimit).A method was proposed to evaluate slope stability by integrating Llimit with monitored displacement data.On-site displacement monitoring and slope state analysis determined the distribution range of asperities,providing theoretical support for slope remediation.Between July 2023 and July 2024,a large landslide located in Shagudu Town,Zhungeer Banner,Ordos,Inner Mongolia,underwent multiple deformation stages.This landslide seriously affected the operations of the Rongwu Expressway.This study initially examined the geological structure of the landslide through geological drilling and surveys.The distribution of asperities in the landslide area was determined through physical and mechanical tests and on-site geological mapping.A layout plan for landslide disposal and monitoring points was developed based on the interface landslide asperity theory.Analysis of 20 days of displacement monitoring data was used to determine asperity distribution and analyze slope movement,informed by asperity theory.This study pioneers the systematic application of asperity theory as the primary framework for analyzing and managing a large-scale interface landslide in engineering practice.Its rationality and effectiveness are rigorously demonstrated through the successful determination of the asperity distribution range within the Rongwu Expressway landslide,leading to effective remediation and favorable monitoring outcomes.This work not only validates the asperity theory for interface landslides but,crucially,establishes a novel,practical method for their stability assessment.Furthermore,a key theoretical advancement is the development of the concept that asperity-controlled main sliding surfaces can induce secondary sliding surfaces,based on field evidence and analysis.展开更多
Simultaneously achieving high strength and high electrical conductivity in Cu–Ni–Si alloys pose a significant challenge, which greatly constrains its applications in the electronics industry. This paper offers a new...Simultaneously achieving high strength and high electrical conductivity in Cu–Ni–Si alloys pose a significant challenge, which greatly constrains its applications in the electronics industry. This paper offers a new pathway to improve properties, by preparation of nanometer lamellar discontinuous precipitates(DPs) arranged with the approximate same direction through a combination of deformationaging and cold rolling process. The strengthening effect is primarily attributed to nanometer-lamellar DPs strengthening and dislocation strengthening mechanism. The accumulation of dislocations at the interface between nanometer lamellar DPs and matrix during cold deformation process can results in the decrease of dislocation density inside the matrix grains, leading to the acceptably slight reduction of electrical conductivity during cold rolling. The alloy exhibits an electrical conductivity of 45.32%IACS(international annealed copper standard, IACS), a tensile strength of 882.67 MPa, and a yield strength of 811.33 MPa by this method. This study can provide a guidance for the composition and microstructure design of a Cu–Ni–Si alloy in the future, by controlling the morphology and distribution of DPs.展开更多
To accurately capture the measurement of bus reliability and evaluate whether the transit system is properly operated an evaluation framework is established to assess the reliability of the transit system from differe...To accurately capture the measurement of bus reliability and evaluate whether the transit system is properly operated an evaluation framework is established to assess the reliability of the transit system from different stratifications including stops routes and network levels.The bus operation data of the Hefei city is analyzed as a case study.Comparison is conducted to show the improvement made by using the advanced method and an example of adding exclusive bus lanes to the existing bus route is provided. The proposed advanced method can avoid the shortcomings of the traditional method.For example the value of the reliability using the traditional coefficient of variation CV is not between 0 and 1 and the value of reliability can decrease with the increase in the transit headway etc. The case study shows that the advanced method can represent the real operation condition of the transit system and can be used to evaluate the transit headway reliability more reasonably.展开更多
基金financially supported by the National Key Research and Development Program of China (No. 2023YFB3812601)the National Natural Science Foundation of China (No. 51925401)the Young Elite Scientists Sponsorship Program by CAST, China (No. 2022QNRC001)。
文摘Machine learning-assisted methods for rapid and accurate prediction of temperature field,mushy zone,and grain size were proposed for the heating−cooling combined mold(HCCM)horizontal continuous casting of C70250 alloy plates.First,finite element simulations of casting processes were carried out with various parameters to build a dataset.Subsequently,different machine learning algorithms were employed to achieve high precision in predicting temperature fields,mushy zone locations,mushy zone inclination angle,and billet grain size.Finally,the process parameters were quickly optimized using a strategy consisting of random generation,prediction,and screening,allowing the mushy zone to be controlled to the desired target.The optimized parameters are 1234℃for heating mold temperature,47 mm/min for casting speed,and 10 L/min for cooling water flow rate.The optimized mushy zone is located in the middle of the second heat insulation section and has an inclination angle of roughly 7°.
文摘Facing increasing passenger and cargo transport demand and limited re-source in the 13th Five-Year period, how to make a breakthrough and substantial progress has become a key issue on planning and the Top-level Design. In this paper we judged and analyzed the current development and potential demand of the energy saving and emission reduction in Beijing traffic industry. Through application of energy and emission prediction model which based on the vehicle activity data, the development goals of “one drop, double control, and triple upgrade” have been put forward. In order to achieve the goal, “5 + 1” development strategies should be implemented, and we also proposed the thinking and recommendations on sustainable development of transportation.
文摘This paper investigated the interaction effects between inventory and transportation strategies in the logistics network. Demand volumes and shipping sizes were simulated as part of a new conceptual model using a discrete event simulation by minimizing the total logistics cost in the supply chain. The experiments indicate that the full truckload scenario leads to cost efficiency and the larger demand size results in smaller cost per unit based on economies of scale. Considering the interaction effects, demand size has a greater impact on cost reduction than shipping size. The total logistics cost in the system is dependent on replenishment rate and flow rates from the higher to the lower echelon. High inventory cost is the result of a fast replenishment rate and frequent orders, while shipping cost is dependent on the flow rates in a process and total travelling time or total travelling distance. Shipping size also has an impact on the level of service and the total cost along with effective order variability.
文摘This study reviews productivity growth in the five major transportation industries in the United States (airline, truck, rail, pipeline, and water) and the pooled transportation industry from 2004 to 2011. We measure the average productivity for these eight years by state in each transportation industry and the annual average productivity by transportation industry. The major findings are that the U.S. transportation industry shows strong and positive productivity growth except that in the years of the global financial crisis in 2007, 2008, and 2010, and among the five transportation industries, the rail and water sectors show the highest productivity growth in 2011.
基金Project(2022YJS073)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(2024YFE0198500)supported by the National Key Research and Development Program of China:Intergovernmental International Science and Technology Innovation CooperationProject(U2469207)supported by the National Natural Science Foundation Railway Innovation and Development Joint Fund Project,China。
文摘Determining earth pressure on jacked pipes is essential for ensuring lining safety and calculating jacking force,especially for deep-buried pipes.To better reflect the soil arching effect resulting from the excavation of rectangular jacked pipes and the distribution of the earth pressure on jacked pipes,we present an analytical solution for predicting the vertical earth pressure on deep-buried rectangular pipe jacking tunnels,incorporating the tunnelling-induced ground loss distribution.Our proposed analytical model consists of the upper multi-layer parabolic soil arch and the lower friction arch.The key parameters(i.e.,width and height of friction arch B and height of parabolic soil arch H 1)are determined according to the existing research,and an analytical solution for K l is derived based on the distribution characteristics of the principal stress rotation angle.With consideration for the transition effect of the mechanical characteristics of the parabolic arch zone,an analytical solution for soil load transfer is derived.The prediction results of our analytical solution are compared with tests and simulation results to validate the effectiveness of the proposed analytical solution.Finally,the effects of different parameters on the soil pressure are discussed.
基金funded by the Natural Science Foundation of Inner Mongolia Autonomous Region(2023JQ03,2023QN05014)the Youth Science and Technology Talents Project of Autonomous Region Colleges and Universities(NJYT22108)。
文摘Loess slopes in cold and arid regions are susceptible to shallow soil degradation,which may trigger severe environmental problems related to soil erosion.To address this environmental challenge,this study selected a compound ecological curing agent composed of gellan gum and guar gum for stabilizing shallow loess slopes.Triaxial compression and disintegration tests were employed to comparatively analyze the effects of compound gum content,mass mix ratio,and curing age on the mechanical and disintegration properties of solidified loess.The curing mechanism was analyzed using scanning electron microscopy(SEM),and the ecological protection effect was monitored for a 60-day period.The results indicate that gellan gum,guar gum,and the compound gum can enhance the mechanical and disintegration properties of loess,promote plant growth,and optimize the ecological environment.However,the combination of gellan gum and guar gum proves more effective than using either gellan gum or guar gum alone.Considering the effects on mechanical properties,disintegration performance,and material economy,the disintegration rate of loess decreases by 75.72%compared to plain loess when the compound glue content is 0.5%,the mixing ratio of gellan gum to guar gum is 3:7 and the curing age is 7 days.Meanwhile,the cohesion and internal friction angle increase by 118.06%and 10.97%,respectively.Moreover,the disintegration performance and mechanical properties of the samples first increase and then decrease with the increase in compound glue and the mix ratio and are basically stabilized after the curing age reaches 7d.
基金supported by Youth Foundation for Research of the Waterborne Transportation Institute.
文摘Structural properties of the ship container logistics network of China(SCLNC)are studied in the light of recent investigations of complex networks.SCLNC is composed of a set of routes and ports located along the sea or river.Network properties including the degree distribution,degree correlations,clustering,shortest path length,centrality and betweenness are studied in different definition of network topology.It is found that geographical constraint plays an important role in the network topology of SCLNC.We also study the traffic flow of SCLNC based on the weighted network representation,and demonstrate the weight distribution can be described by power law or exponential function depending on the assumed definition of network topology.Other features related to SCLNC are also investigated.
文摘Digital Twin (DT) technology is revolutionizing the railway sector by providing a virtual replica of physical systems, enabling real-time monitoring, predictive maintenance, and enhanced decision-making. This systematic literature review examines the status, enabling technologies, case studies, and frameworks for DT applications in railway systems with 91 selected papers from Scopus, Web of Science, IEEE, and the Snowballing Technique. The review focuses on four primary subsystems: tracks, civil structures, vehicles, and overhead contact line structures. Key findings reveal that DT has successfully optimized maintenance strategies, improved operational efficiency, and enhanced system safety. Internet of Things (IoT) devices, Artificial Intelligence (AI), machine learning, and cloud computing are critical in implementing DT models. However, challenges like data integration, high implementation costs, and cybersecurity risks remain, necessitating the discussed implications. Future research should focus on improving data interoperability, reducing costs through scalable cloud-based solutions, and addressing cybersecurity vulnerabilities. DT technology has the potential to revolutionize railway infrastructure management, ensuring greater efficiency, safety, and sustainability.
文摘Integrating autonomous vehicles (AVs) and autonomous parking spaces (APS) marks a transformative development in urban mobility and sustainability. This paper reflects on these technologies’ historical evolution, current interdependence, and future potential through the lens of environmental, social, and economic sustainability. Historically, parking systems evolved from manual designs to automated processes yet remained focused on convenience rather than sustainability. Presently, advancements in smart infrastructure and vehicle-to-infrastructure (V2I) communication have enabled AVs and APS to operate as a cohesive system, optimizing space, energy, and transportation efficiency. Looking ahead, the seamless integration of AVs and APS into broader smart city ecosystems promises to redefine urban landscapes by repurposing traditional parking infrastructure into multifunctional spaces and supporting renewable energy initiatives. These technologies align with global sustainability goals by mitigating emissions, reducing urban sprawl, and fostering adaptive land uses. This reflection highlights the need for collaborative efforts among stakeholders to address regulatory and technological challenges, ensuring the equitable and efficient deployment of AVs and APS for smarter, greener cities.
基金Funded by the Natural Science Foundation of Inner Mongolia Autonomous Region(No.2024QN05023)High Level Talent Research Launch Foundation of Inner Mongolia University(No.10000-22311201/008)。
文摘Electrochemical impedance spectroscopy(EIS)was used to examine the electrical properties of metakaolin(MK)cement-based materials at elevated temperatures.We utilized a new equivalent circuit to investigate the EIS results of cementitious materials blended with MK at these temperatures.A new evaluation method to high temperature damage is proposed.The findings show that both elevated temperatures and MK contents in cement mortar can impact the impedance spectra’s form properties.However,the residual compressive strength of the MK-blended cementitious material at elevated temperatures does not improve with the addition of MK.A quantitative relationship between the electrochemical parameters of the new equivalent circuit and the residual compressive strength is determined.The degree of high-temperature damage to cementitious materials can be evaluated based on these electrochemical parameters,providing a new approach for evaluating the high-temperature damage of MK-blend cementitious materials.
基金support from Interdisciplinary Research Project for Young Teachers of USTB Fundamental Research Funds for the Central Universities(Grant no.FRF-IDRY-23-030).
文摘Solute atoms and precipitates significantly influence the mechanical properties of Mg alloys.Previous studies have mainly focused on the segregation behaviors of Mg alloys after annealing.In this study,we investigated the segregation behaviors of an Mg-RE alloy under deformation.We found that the enrichment of solute atoms occurred in{101^(-)1}compressive twin boundaries under compression at 298 K without any annealing in an Mg-RE alloy by scanning transmission electron microscopy and energy-dispersive X-ray analysis.The segregated solutes and precipitates impeded the twin growth,partially contributing to the formation of small-sized{101^(-)1}compressive twins.This research indicates the twin boundaries can be strengthened by segregated solutes and precipitates formed under deformation at room temperature.
文摘This paper presents a method for fabricating a low-cost,highly reproducible miniature optical fiber Fabry-Perot(FP)sensor based on a polydimethylsiloxane(PDMS)end-cap structure.The FP cavity end-cap is formed by the optical fiber end-face and a PDMS droplet deposited onto it.The PDMS deposition is achieved by immersing the fiber end into pre-cured PDMS at a fixed speed,a process requiring careful control of PDMS viscosity and surface tension.By leveraging PDMS’s excellent thermal expansion coefficient,Poisson’s ratio,and other parameters,this method achieves high reproducibility via viscosity-optimized pre-curing,enhanced sensitivity for temperature measurements,and significant cost reduction versus commercial counterparts.Fiber FP sensors are increasingly widely used in biomedical and precision detection fields owing to their significant advantages,including small size,light weight,high sensitivity,and immunity to electromagnetic interference.In the fabrication of fiber FP sensors,using polymer materials is an effective technical approach.These polymers can be applied as coatings on the optical fiber end-face or as interlayer materials embedded between fibers to form the FP cavity structure,which not only significantly improves the overall sensor performance,but also enhances its sensitivity to changes in temperature,pressure,and refractive index.In the final part of this study,we successfully validated the exceptional performance of the PDMS end-cap based fiber FP sensor in detecting different temperatures conditions.Experimental results demonstrate a temperature sensitivity of 0.752 nm/℃for sensors with a 60-μm PDMS end-cap,further confirming the sensor’s reliability and efficiency in practical applications.
基金Supported by the Central Public-Interest Scientific Institution Basal Research Fund(2023-9062)the Transport Power Pilot Project(2021-C334)。
文摘The quality of rebar welds directly impacts the overall service performance of highway infrastructure.However,current assessments of weld appearance quality primarily rely on traditional inspection methods such as manual visual inspection,which suffer from significant limitations in accuracy,reliability,and efficiency.Given the increasing demand for safety performance inspections of highway infrastructure in China,traditional methods struggle to meet modern rapid inspection requirements.Therefore,this study proposes the design of a portable,non-destructive inspection device for rebar weld appearance,utilizing visible light vision and line-structured light 3D scanning technology.The device is equipped with an STM32 master control chip to manage encoder reading,scanning laser control,ring fill light,industrial camera synchronization,image acquisition,and serial port command transmission.Additionally,a weld image processing and detection software system was developed to receive,store,and identify weld defects.A field inspection prototype was created and subjected to various defect weld detection experiments in a laboratory setting.Experimental results demonstrate that the device can accurately measure weld parameters by acquiring multimodal images,fulfilling defect detection requirements.The device features high detection accuracy,portability,and user-friendliness,making it significant for the objective inspection and evaluation of rebar weld appearance and welding quality.
基金supported by the National Natural Science Foundation of China(Nos.52271295,52088102).
文摘To propel the application of a bottom-hinged flap breakwater in real sea conditions,a two-dimensional computational fluid dynamics numerical model was conducted to investigate the pitching motion response and wave attenuation in random waves.First,the flow velocity distribution characteristic of the pitching flap at typical times was summarized.Then,the effects of random wave and flap parameters on the flap’s significant pitching angle amplitude θ_(s) and hydrodynamic coefficients were investigated.The results reveal that θ_(s) and wave reflection coefficient K_(r) values increase with increasing significant wave height Hs,random wave steepnessλs,and flap relative height.As Hs andλs increase,the wave transmission coefficient K_(t) increases while the wave dissipation coefficient K_(d) decreases.Additionally,K_(t) decreases with increasing flap relative height.With increasing equivalent damping coefficient ratio,θ_(s) and K_(t) decrease,while K_(r) and K_(d) increase.The relationships betweenλs and flap relative height on the one hand andθ_(s),K_(r),K_(t),and K_(d) in random waves on the other hand are compared to those in regular waves.Based on the equal incident wave energy and the equal incident wave energy flux,the pitching flap performs better in the wave attenuation capability under random waves than in regular waves.Finally,the dimensionless parameters with respect to random wave and flap were used to derive the K_(r) and K_(t) for-mulae,which were validated with the related data.
基金supported by the National Key Research and Development Program of China(No.2022YFB4600302)the Fundamental Research Funds for the Central Universities,China(No.FRF-IDRY-23-011).
文摘Custom 465(C465)is a martensitic stainless steel known for its high strength,toughness,and corrosion resistance,widely used in aerospace,automotive,and medical industries.However,limited work has been conducted on its additive manufacturing(AM)and no dedicated heat treatments have been developed for additively manufactured C465 to optimize its strength-ductility trade-off.In this work,the C465 was fabricated via laser powder bed fusion.The effect of hot isostatic pressing,solid solution,cryogenic treatment(−78.5℃),and aging on the composition homogenization,austenite-to-martensite transition,and Ni_(3)Ti precipitation were systemically investigated.The atom probe tomography analysis reveals that Mo atoms accumulate on Ni_(3)Ti precipitate surfaces and inhibits the Ni_(3)Ti growth,con-tributing to the enhanced strength of C465.The modified heat treatment for additively manufactured C465 reaches comparable tensile strength with the wrought counterpart,yielding an ultimate tensile strength of 1773 MPa,yield strength of 1686 MPa,and elongation of 6.5%.A yield strength calculation model was proposed and validated with measured strength under various heat treatments,providing valuable insight for heat treatment design towards diverse industrial applications.
基金financially supported by the National Key Research and Development Program of China(No.2022YFB3706901)the National Natural Science Foundation of China(No.52090041)the Young Elite Scientists Sponsorship Program by CAST(No.2022QNRC 001).
文摘Digital modeling and autonomous control of the die forging process are significant challenges in realizing high-quality intelli-gent forging of components.Using the die forging of AA2014 aluminum alloy as a case study,a machine-learning-assisted method for di-gital modeling of the forging force and autonomous control in response to forging parameter disturbances was proposed.First,finite ele-ment simulations of the forging processes were conducted under varying friction factors,die temperatures,billet temperatures,and for-ging velocities,and the sample data,including process parameters and forging force under different forging strokes,were gathered.Pre-diction models for the forging force were established using the support vector regression algorithm.The prediction error of F_(f),that is,the forging force required to fill the die cavity fully,was as low as 4.1%.To further improve the prediction accuracy of the model for the ac-tual F_(f),two rounds of iterative forging experiments were conducted using the Bayesian optimization algorithm,and the prediction error of F_(f) in the forging experiments was reduced from 6.0%to 1.5%.Finally,the prediction model of F_(f) combined with a genetic algorithm was used to establish an autonomous optimization strategy for the forging velocity at each stage of the forging stroke,when the billet and die temperatures were disturbed,which realized the autonomous control in response to disturbances.In cases of−20 or−40℃ reductions in the die and billet temperatures,forging experiments conducted with the autonomous optimization strategy maintained the measured F_(f) around the target value of 180 t,with the relative error ranging from−1.3%to+3.1%.This work provides a reference for the study of di-gital modeling and autonomous optimization control of quality factors in the forging process.
基金supported by the Advanced Materials-National Science and Technology Major Project(No.2025ZD0619700)National Natural Science Foundation of China(No.52401002,92570301)+1 种基金China Postdoctoral Science Foundation funded project(No.2024M760200)Fundamental Research Funds for the Central Universities(No.FRF-BD-25-007).
文摘Designing low-density,high-strength Mg-Li alloys is a major challenge in achieving extreme lightweighting of high-end equipment.This study proposes an interpretable machine learning strategy to simultaneously enhance the mechanical properties and corrosion resistance of Mg-Li alloy.Key alloy factors(KAFs)influencing ultimate tensile strength(UTS),elongation(EL),and corrosion rate(CR)were identified through alloy factor construction and screening.Using KAFs and processing parameters as inputs,gradient boosting regression models for UTS,EL,and CR were established,achieving the coefficients of determination of test-set above 0.85.Then,SHapley Additive exPlanations(SHAP)analysis quantified the impact of KAFs,and an element evaluation method was established to identify Al,Si,Ca,and Zn as candidates for alloy design.Finally,three new alloys were designed via multi-objective optimization.In the hot-extruded state,they exhibited UTS of 253∼273 MPa,EL of 18.4%∼27.9%,CR of 0.55∼1.61 mg/(cm^(2)·day),and ρ of 1.49∼1.54 g/cm^(3).Compared to LAZ103,the new alloys show 34%∼44%higher UTS,35%∼79%lower CR,and comparable ρ.Microstructural analysis revealed increasedα-Mg,decreasedβ-Li,reduced coarse secondary phases,and fine Ca-/Si-rich precipitates which are conducive to grain refinement and dislocation density increasing,synergistically enhancing comprehensive property.
基金supported by the National Natural Science Foundation of China(Grant No:12362034)the Science and Technology Plan Project of Inner Mongolia Autonomous Region(Grant No:2022YFSH0047)Talent Project of Inner Mongolia Autonomous Region(DC2300001439,DC2200000913).
文摘Varied slope structures have different landslide initiation mechanisms.However,the role of interfacial asperities in controlling sliding initiation is unclear.This study develops a novel analytical method for interface mechanisms in practical landslide scenarios.Based on asperity theory,theoretical derivations were conducted,yielding an equilibrium equation grounded in the maximum shear length of asperities(Llimit).A method was proposed to evaluate slope stability by integrating Llimit with monitored displacement data.On-site displacement monitoring and slope state analysis determined the distribution range of asperities,providing theoretical support for slope remediation.Between July 2023 and July 2024,a large landslide located in Shagudu Town,Zhungeer Banner,Ordos,Inner Mongolia,underwent multiple deformation stages.This landslide seriously affected the operations of the Rongwu Expressway.This study initially examined the geological structure of the landslide through geological drilling and surveys.The distribution of asperities in the landslide area was determined through physical and mechanical tests and on-site geological mapping.A layout plan for landslide disposal and monitoring points was developed based on the interface landslide asperity theory.Analysis of 20 days of displacement monitoring data was used to determine asperity distribution and analyze slope movement,informed by asperity theory.This study pioneers the systematic application of asperity theory as the primary framework for analyzing and managing a large-scale interface landslide in engineering practice.Its rationality and effectiveness are rigorously demonstrated through the successful determination of the asperity distribution range within the Rongwu Expressway landslide,leading to effective remediation and favorable monitoring outcomes.This work not only validates the asperity theory for interface landslides but,crucially,establishes a novel,practical method for their stability assessment.Furthermore,a key theoretical advancement is the development of the concept that asperity-controlled main sliding surfaces can induce secondary sliding surfaces,based on field evidence and analysis.
基金supported by the National Key Research and Development Program of China (No. 2023YFB3812601)the National Natural Science Founda tion of China (Nos. 51925401, 92066205, and 92266301)。
文摘Simultaneously achieving high strength and high electrical conductivity in Cu–Ni–Si alloys pose a significant challenge, which greatly constrains its applications in the electronics industry. This paper offers a new pathway to improve properties, by preparation of nanometer lamellar discontinuous precipitates(DPs) arranged with the approximate same direction through a combination of deformationaging and cold rolling process. The strengthening effect is primarily attributed to nanometer-lamellar DPs strengthening and dislocation strengthening mechanism. The accumulation of dislocations at the interface between nanometer lamellar DPs and matrix during cold deformation process can results in the decrease of dislocation density inside the matrix grains, leading to the acceptably slight reduction of electrical conductivity during cold rolling. The alloy exhibits an electrical conductivity of 45.32%IACS(international annealed copper standard, IACS), a tensile strength of 882.67 MPa, and a yield strength of 811.33 MPa by this method. This study can provide a guidance for the composition and microstructure design of a Cu–Ni–Si alloy in the future, by controlling the morphology and distribution of DPs.
基金The National Basic Research Program of China(973 Program)(No.2012CB725402)the National Natural Science Foundation of China(No.51208099,50978057)
文摘To accurately capture the measurement of bus reliability and evaluate whether the transit system is properly operated an evaluation framework is established to assess the reliability of the transit system from different stratifications including stops routes and network levels.The bus operation data of the Hefei city is analyzed as a case study.Comparison is conducted to show the improvement made by using the advanced method and an example of adding exclusive bus lanes to the existing bus route is provided. The proposed advanced method can avoid the shortcomings of the traditional method.For example the value of the reliability using the traditional coefficient of variation CV is not between 0 and 1 and the value of reliability can decrease with the increase in the transit headway etc. The case study shows that the advanced method can represent the real operation condition of the transit system and can be used to evaluate the transit headway reliability more reasonably.
