Semisubmersible naval ships are versatile military crafts that combine the advantageous features of high-speed planing crafts and submarines.At-surface,these ships are designed to provide sufficient speed and maneuver...Semisubmersible naval ships are versatile military crafts that combine the advantageous features of high-speed planing crafts and submarines.At-surface,these ships are designed to provide sufficient speed and maneuverability.Additionally,they can perform shallow dives,offering low visual and acoustic detectability.Therefore,the hydrodynamic design of a semisubmersible naval ship should address at-surface and submerged conditions.In this study,Numerical analyses were performed using a semisubmersible hull form to analyze its hydrodynamic features,including resistance,powering,and maneuvering.The simulations were conducted with Star CCM+version 2302,a commercial package program that solves URANS equations using the SST k-ωturbulence model.The flow analysis was divided into two parts:at-surface simulations and shallowly submerged simulations.At-surface simulations cover the resistance,powering,trim,and sinkage at transition and planing regimes,with corresponding Froude numbers ranging from 0.42 to 1.69.Shallowly submerged simulations were performed at seven different submergence depths,ranging from D/LOA=0.0635 to D/LOA=0.635,and at two different speeds with Froude numbers of 0.21 and 0.33.The behaviors of the hydrodynamic forces and pitching moment for different operation depths were comprehensively analyzed.The results of the numerical analyses provide valuable insights into the hydrodynamic performance of semisubmersible naval ships,highlighting the critical factors influencing their resistance,powering,and maneuvering capabilities in both at-surface and submerged conditions.展开更多
The squeezing deformation of surrounding rock is an important factor restricting the safe construction and long-term operation of tunnels when a tunnel passes through soft strata with high ground stress.Under such sof...The squeezing deformation of surrounding rock is an important factor restricting the safe construction and long-term operation of tunnels when a tunnel passes through soft strata with high ground stress.Under such soft rock geological conditions,the large deformation of the surrounding rock can easily lead to the failure of supporting structures,including shotcrete cracks,spalling,and steel arch distortion.To improve the lining support performance during the large deformation of squeezed surrounding rock,this work selects aluminum foam with densities of 0.25 g/cm3,0.42 g/cm3 and 0.61 g/cm3 as the buffer layer material and carries out uniaxial confined compression tests.Through the evaluation and analysis of energy absorption and the comparison of the yield pressure of aluminum foam with those of other cushioning materials and yield pressure support systems,the strength,deformation and energy absorption of aluminum foam with a density of 0.25 g/cm3 meet the yield pressure performance requirements.The numerical model of the buffer layer yielding support system is then established via the finite element analysis software ABAQUS,and the influence of the buffer layer setting on the lining support is analyzed.Compared with the conventional support scheme,the addition of an aluminum foam buffer layer can reduce the stress and deformation of the primary support and secondary lining.The maximum and minimum principal stresses of the primary support are reduced by 13%and 15%,respectively.The maximum and minimum principal stresses of the secondary lining are reduced by 15%and 12%,respectively,and the displacement deformation of the secondary lining position is reduced by 15%.In summary,the application of aluminum foam buffer layer can reduce the stress and deformation of the primary support and secondary lining,improve the stress safety of the support and reduce the deformation of the support.展开更多
1.Introduction As China’s first floating production platform in ultra-deepwater,the“Deep Sea No.1”energy station is a milestone in China’s deepwater resource utilization.The energy station is located in the LS17-2...1.Introduction As China’s first floating production platform in ultra-deepwater,the“Deep Sea No.1”energy station is a milestone in China’s deepwater resource utilization.The energy station is located in the LS17-2 gas field,150 km off the southeast coast of Hainan Island,China.It is a semi-submersible platform(Fig.1)with a displacement of 101 thousand tonnes and an operational draft of 35 to 40 m.The platform is permanently moored in 1422 m water by 16 chain-polyester-chain mooring lines in a 4×4 pattern,and six steel catenary risers(SCRs)are attached to the platform.It is the world’s first and only semi-submersible platform with the function of condensate storage,so it can be regarded as a floating production storage and offloading(FPSO)unit.With the ability to produce 3 billion m3 of natural gas each year(enough for over 10 million families),the Deep Sea No.1 energy station is a key step toward China’s energy independence.The LS17-2 gas field,where the Deep Sea No.1 energy station is located,was discovered in 2014.Plans for its development were made in 2015,followed by research and a preliminary design.Deep Sea No.1 went into operation on June 25,2021,and will operate onsite continuously without dry-docking for 30 years.展开更多
The deformation caused by tunnel excavation is quite important for safety,especially when it is adjacent to the existing tunnel.Nevertheless,the investigation of deformation characteristics in overlapped curved shield...The deformation caused by tunnel excavation is quite important for safety,especially when it is adjacent to the existing tunnel.Nevertheless,the investigation of deformation characteristics in overlapped curved shield tunneling remains inadequate.The analytical solution for calculating the deformation of the ground and existing tunnel induced by overlapped curved shield tunneling is derived by the Mirror theory,Mindlin solution and Euler-Bernoulli-Pasternak model,subsequently validated through both finite element simulation and field monitoring.It is determined that the overcutting plays a crucial role in the ground settlement resulting from curved shield tunneling compared to straight shield tunneling.The longitudinal settlement distribution can be categorized into five areas,with the area near the tunnel surface experiencing the most dramatic settlement changes.The deformation of the existing tunnel varies most significantly with turning radius compared to tunnel clearance and grouting pressure,especially when the turning radius is less than 30 times the tunnel diameter.The tunnel crown exhibits larger displacement than the tunnel bottom,resulting in a distinctive‘vertical egg'shape.Furthermore,an optimized overcutting mode is proposed,involving precise control of the extension speed and angular velocity of the overcutting cutter,which effectively mitigates ground deformation,ensuring the protection of the existing tunnel during the construction.展开更多
Ship outfitting is a key process in shipbuilding.Efficient and high-quality ship outfitting is a top priority for modern shipyards.These activities are conducted at different stations of shipyards.The outfitting plan ...Ship outfitting is a key process in shipbuilding.Efficient and high-quality ship outfitting is a top priority for modern shipyards.These activities are conducted at different stations of shipyards.The outfitting plan is one of the crucial issues in shipbuilding.In this paper,production scheduling and material ordering with endogenous uncertainty of the outfitting process are investigated.The uncertain factors in outfitting equipment production are usually decision-related,which leads to difficulties in addressing uncertainties in the outfitting production workshops before production is conducted according to plan.This uncertainty is regarded as endogenous uncertainty and can be treated as non-anticipativity constraints in the model.To address this problem,a stochastic two-stage programming model with endogenous uncertainty is established to optimize the outfitting job scheduling and raw material ordering process.A practical case of the shipyard of China Merchants Heavy Industry Co.,Ltd.is used to evaluate the performance of the proposed method.Satisfactory results are achieved at the lowest expected total cost as the complete kit rate of outfitting equipment is improved and emergency replenishment is reduced.展开更多
Autonomous Underwater Vehicles(AUVs)are pivotal for deep-sea exploration and resource exploitation,yet their reliability in extreme underwater environments remains a critical barrier to widespread deployment.Through s...Autonomous Underwater Vehicles(AUVs)are pivotal for deep-sea exploration and resource exploitation,yet their reliability in extreme underwater environments remains a critical barrier to widespread deployment.Through systematic analysis of 150 peer-reviewed studies employing mixed-methods research,this review yields three principal advancements to the reliability analysis of AUVs.First,based on the hierarchical functional division of AUVs into six subsystems(propulsion system,navigation system,communication system,power system,environmental detection system,and emergency system),this study systematically identifies the primary failure modes and potential failure causes of each subsystem,providing theoretical support for fault diagnosis and reliability optimization.Subsequently,a comprehensive review of AUV reliability analysis methods is conducted from three perspectives:analytical methods,simulated methods,and surrogate model methods.The applicability and limitations of each method are critically analyzed to offer insights into their suitability for engineering applications.Finally,the study highlights key challenges and research hotpots in AUV reliability analysis,including reliability analysis under limited data,AI-driven reliability analysis,and human reliability analysis.Furthermore,the potential of multi-sensor data fusion,edge computing,and advanced materials in enhancing AUV environmental adaptability and reliability is explored.展开更多
In this paper,a type of reinforcing structure for composite shell with single and through hole is presented.The experimental tests for the composite shells without hole,with single hole and reinforced structure,with t...In this paper,a type of reinforcing structure for composite shell with single and through hole is presented.The experimental tests for the composite shells without hole,with single hole and reinforced structure,with through hole and reinforced structure subjected to hydrostatic pressure were carried out by the designed experimental test system.The mechanical responses of the composite shells under hydrostatic pressure are obtained by the high-speed camera and strain measurement.The results show that the entire deformation process of the shell can be divided into three:uniform compression,"buckling mode formation"and buckling.The"buckling mode formation"process is captured and reported for the first time.For the composite shell with single hole,the proposed reinforcing structure has a significant reinforcement effect on the shell and the buckling capacity of the shell is not weaker than the complete composite shell.For the composite shell with through hole,sealing effect can be achieved by the proposed reinforcing structure,but the buckling capacity of the shell after reinforcement can only reach 77%of the original buckling capacity.展开更多
The maneuverability and stealth of aerial-aquatic vehicles(AAVs)is of significant importance for future integrated air-sea combat missions.To improve the maneuverability and stealth of AAVs near the water surface,this...The maneuverability and stealth of aerial-aquatic vehicles(AAVs)is of significant importance for future integrated air-sea combat missions.To improve the maneuverability and stealth of AAVs near the water surface,this paper proposed a high-maneuverability skipping motion strategy for the tandem twin-rotor AAV,inspired by the motion behavior of the flying fish to avoid aquatic and aerial predators near the water surface.The novel tandem twin-rotor AAV was employed as the research subject and a strategybased ADRC control method for validation,comparing it with a strategy-based PID control method.The results indicate that both control methods enable the designed AAV to achieve high stealth and maneuverability near the water surface with robust control stability.The strategy-based ADRC control method exhibits a certain advantage in controlling height,pitch angle,and reducing impact force.This motion strategy will offer an inspiring approach for the practical application of AAVs to some extent.展开更多
The utilization of unmanned aerial vehicle(UAV) relays in cooperative communication has gained considerable attention in recent years.However,the current research is mostly based on fixed base stations and users,lacki...The utilization of unmanned aerial vehicle(UAV) relays in cooperative communication has gained considerable attention in recent years.However,the current research is mostly based on fixed base stations and users,lacking sufficient exploration of scenarios where communication nodes are in motion.This paper presents a multi-destination vehicle communication system based on decode-and-forward(DF)UAV relays,where source and destination vehicles are moving and an internal eavesdropper intercepts messages from UAV.The closed-form expressions for system outage probability and secrecy outage probability are derived to analyze the reliability and security of the system.Furthermore,the impact of the UAV's position,signal transmission power,and system time allocation ratio on the system's performance are also analyzed.The numerical simulation results validate the accuracy of the derived formulas and confirm the correctness of the analysis.The appropriate time allocation ratio significantly enhances the security performance of system under various environmental conditions.展开更多
Based on inspection data,the authors analyze and summarize the main types and distribution characteristics of tunnel structural defects.These defects are classified into three types:surface defects,internal defects,an...Based on inspection data,the authors analyze and summarize the main types and distribution characteristics of tunnel structural defects.These defects are classified into three types:surface defects,internal defects,and defects behind the structure.To address the need for rapid detection of different defect types,the current state of rapid detection technologies and equipment,both domestically and internationally,is systematically reviewed.The research reveals that surface defect detection technologies and equipment have developed rapidly in recent years.Notably,the integration of machine vision and laser scanning technologies have significantly improved detection efficiency and accuracy,achieving crack detection precision of up to 0.1 mm.However,the non-contact rapid detection of internal and behind-the-structure defects remains constrained by hardware limitations,with traditional detection remaining dominant.Nevertheless,phased array radar,ultrasonic,and acoustic vibration detection technologies have become research hotspots in recent years,offering promising directions for detecting these challenging defect types.Additionally,the application of multisensor fusion technology in rapid detection equipment has further enhanced detection capabilities.Devices such as cameras,3D laser scanners,infrared thermal imagers,and radar demonstrate significant advantages in rapid detection.Future research in tunnel inspection should prioritize breakthroughs in rapid detection technologies for internal and behind-the-structure defects.Efforts should also focus on developing multifunctional integrated detection vehicles that can simultaneously inspect both surface and internal structures.Furthermore,progress in fully automated,intelligent systems with precise defect identification and real-time reporting will be essential to significantly improve the efficiency and accuracy of tunnel inspection.展开更多
0 INTRODUCTION In recent years,modern railways have been actively under construction in the complex mountainous area of Southwest China.However,rockfall poses a significant threat to both construction and operation ph...0 INTRODUCTION In recent years,modern railways have been actively under construction in the complex mountainous area of Southwest China.However,rockfall poses a significant threat to both construction and operation phases of railway projects(Yan et al.,2023;Chen et al.,2022;Fanos and Pradhan,2018).展开更多
The advancement of 6G wireless communication technology has facilitated the integration of Vehicular Ad-hoc Networks(VANETs).However,the messages transmitted over the public channel in the open and dynamic VANETs are ...The advancement of 6G wireless communication technology has facilitated the integration of Vehicular Ad-hoc Networks(VANETs).However,the messages transmitted over the public channel in the open and dynamic VANETs are vulnerable to malicious attacks.Although numerous researchers have proposed authentication schemes to enhance the security of Vehicle-to-Vehicle(V2V)communication,most existing methodologies face two significant challenges:(1)the majority of the schemes are not lightweight enough to support realtime message interaction among vehicles;(2)the sensitive information like identity and position is at risk of being compromised.To tackle these issues,we propose a lightweight dual authentication protocol for V2V communication based on Physical Unclonable Function(PUF).The proposed scheme accomplishes dual authentication between vehicles by the combination of Zero-Knowledge Proof(ZKP)and MASK function.The security analysis proves that our scheme provides both anonymous authentication and information unlinkability.Additionally,the performance analysis demonstrates that the computation overhead of our scheme is approximately reduced 23.4% compared to the state-of-the-art schemes.The practical simulation conducted in a 6G network environment demonstrates the feasibility of 6G-based VANETs and their potential for future advancements.展开更多
The safety of the initial support during the construction of inclined shafts in tunnels traversing through high-hydraulic-pressure surrounding rocks is paramount.This study examines a high-hydraulic-pressure inclined ...The safety of the initial support during the construction of inclined shafts in tunnels traversing through high-hydraulic-pressure surrounding rocks is paramount.This study examines a high-hydraulic-pressure inclined shaft of a tunnel in Western Sichuan Province to analyze the damage characteristics of the initial support and propose a radial drainage and decompression treatment method.Field monitoring was conducted to assess the load and deformation of the initial support structure,and on-site investigations identified the distribution of cracked areas.In addition,numerical simulations were performed to evaluate the force and deformation characteristics of the initial support structure,which were then compared with field observations for validation.The variations in the lateral pressure coefficient and water pressure were evaluated.The results revealed that damage was primarily concentrated in the shoulder,spring line,and knee areas,with the bending moment at the knee increasing by up to 66.9%.The application of the radial drainage and decompression treatment method effectively reduced water pressure loads on the initial support.Post-treatment analysis indicated significant reductions in axial force and bending moment,enhancing structural stability.These findings provide valuable insights for improving the safety and durability of initial support systems in inclined shafts of high-hydraulicpressure railroad tunnels.展开更多
This paper provides a comprehensive review of various experimental methods used to study carbon corrosion in automotive polymer exchange membrane fuel cells.Quantifying the extent of carbon corrosion is essential for ...This paper provides a comprehensive review of various experimental methods used to study carbon corrosion in automotive polymer exchange membrane fuel cells.Quantifying the extent of carbon corrosion is essential for advancing the technology and implementing effective mitigation strategies.While studying degradation events directly within a real-world fuel cell vehicle offers the most reliable insights,the high costs and time demands make it necessary to develop specialised experimental techniques that provide high-resolution data more efficiently and cost-effectively.This review explores the various experimental approaches utilised in automotive application induced carbon corrosion studies globally,including load profiles,test setups,break-in procedures,and cell recovery protocols.In this paper,emphasis is placed on the standardised procedures proposed by leading institutions worldwide,accompanied by critical discussions on these protocols.Furthermore,the paper highlights modified or innovative procedures developed by smaller institutions,universities,and individual researchers,thereby offering a comprehensive overview essential for carbon corrosion analysis.The review also discusses the fundamental principles,benefits,and limitations of various procedures,offering guidance on selecting the most appropriate approach for a given study.Lastly,it addresses the limitations within the current body of literature and outlines potential future prospects.展开更多
Pre-injection is a technique that involves injecting grout materials into the ground prior to excavation,with the aim of stabilizing the surrounding rock mass.This paper introduces an analytical closed-form model for ...Pre-injection is a technique that involves injecting grout materials into the ground prior to excavation,with the aim of stabilizing the surrounding rock mass.This paper introduces an analytical closed-form model for determining the ground reaction curve of tunnels in rock masses exhibiting elastic-brittleplastic behavior and adhering to the Mohr-Coulomb failure criterion.The model incorporates the reinforced region created by the pre-injection method.When the rock mass is reinforced through preinjection,plastic regions can form independently in both the natural and injected rock masses.This leads to six distinct modes of the problem.The analytical model presented in this paper considers three possible scenarios for the development of plastic regions.Each scenario comprises four stages,with each stage representing a different mode of the problem.While injecting the rock mass can enhance its strength and stiffness,it may also increase the brittleness of the injected rock mass and create stress concentrations within it,particularly when brittle grouts are used.As a result,this can elevate the risk of rockburst due to unstable failure.The results obtained from the model demonstrate that ductile grout performs exceptionally well in controlling tunnel convergence in rock masses,as it accommodates deformation without sudden failure,even in squeezing rock mass conditions.Conversely,the use of brittle grouts should be approached with caution,particularly in squeezing rock masses,due to their susceptibility to rockburst incidents.展开更多
The stability of the tunnel portal slope is crucial for ensuring safe tunnel construction.Thus,a sound stability evaluation is of significance.Given the unique geological characteristics of tunnel portal slopes,it is ...The stability of the tunnel portal slope is crucial for ensuring safe tunnel construction.Thus,a sound stability evaluation is of significance.Given the unique geological characteristics of tunnel portal slopes,it is necessary to establish a specific evaluation indicator system that differs from those used for ordinary slopes.Based on the unascertained measure method,uncertainties in the indicator are addressed by introducing the left and right half cloud asymmetric cloud model to optimize the linear membership function.The subjectivity of confidence criterion level identification is also improved by using the Euclidean distance method.Thus,a stability evaluation model for the tunnel portal slope is established based on the improved unascertained measure method.Finally,using the collected tunnel portal slope data,the results of four evaluation methods are compared with the safety factor levels.The evaluation methods include the traditional unascertained measure method,the method improved by using the left and right half cloud asymmetric cloud model,the method improved by using the Euclidean distance method,and the method improved by using both the left and right half cloud asymmetric cloud model and the Euclidean distance method.The results show that the accuracy rates of these four methods are 50%,55%,85%,and 90%,respectively.Among them,the joint improvement method has the slightest deviation,with only one level,while the other three methods had deviations of two levels.This result verifies the stability and effectiveness of the joint improvement method,providing a reference for tunnel portal slope stability evaluation.展开更多
The transformation from multibody models to lumped-parameter models is a crucial aspect of vehicle dynamics research.The velocity transformation method is adopted in this research,and the suspension multibody model is...The transformation from multibody models to lumped-parameter models is a crucial aspect of vehicle dynamics research.The velocity transformation method is adopted in this research,and the suspension multibody model is described using only one degree of freedom.It is found that the equivalent mass of the system is time-dependent during the simulation process,as observed in numerical simulations.Further symbolic calculations are conducted to derive the analytical form of the equivalent mass,and the results show that once the static parameters are determined,the equivalent mass of the suspension system is determined solely by the vertical position of the suspension upright,which reveals the kinematics characteristic of the equivalent mass of the suspension system.It is found that the equivalent mass experiences smaller changes when the suspension is compressed from the middle position,but larger changes when the suspension is extended.Furthermore,by comparing the multibody model,the lumped-parameter model with static mass,and the proposed lumped-parameter model considering the kinematics characteristic of the equivalent unsprung mass,the proposed model produces simulation results that more closely match the original multibody model than the model with static mass.The improvements in accuracy can be up to 20%under certain evaluation metrics.展开更多
文摘Semisubmersible naval ships are versatile military crafts that combine the advantageous features of high-speed planing crafts and submarines.At-surface,these ships are designed to provide sufficient speed and maneuverability.Additionally,they can perform shallow dives,offering low visual and acoustic detectability.Therefore,the hydrodynamic design of a semisubmersible naval ship should address at-surface and submerged conditions.In this study,Numerical analyses were performed using a semisubmersible hull form to analyze its hydrodynamic features,including resistance,powering,and maneuvering.The simulations were conducted with Star CCM+version 2302,a commercial package program that solves URANS equations using the SST k-ωturbulence model.The flow analysis was divided into two parts:at-surface simulations and shallowly submerged simulations.At-surface simulations cover the resistance,powering,trim,and sinkage at transition and planing regimes,with corresponding Froude numbers ranging from 0.42 to 1.69.Shallowly submerged simulations were performed at seven different submergence depths,ranging from D/LOA=0.0635 to D/LOA=0.635,and at two different speeds with Froude numbers of 0.21 and 0.33.The behaviors of the hydrodynamic forces and pitching moment for different operation depths were comprehensively analyzed.The results of the numerical analyses provide valuable insights into the hydrodynamic performance of semisubmersible naval ships,highlighting the critical factors influencing their resistance,powering,and maneuvering capabilities in both at-surface and submerged conditions.
基金the support of the National Natural Science Foundation of China(Grant No.42207199)Scientific Research Project of Education of Zhejiang Province(No.Y202351343)+1 种基金Zhejiang Postdoctoral Scientific Research Project(Grant Nos.ZJ2022155,ZJ2022156)Zhejiang Province International Science and Technology Cooperation Base Open Fund Project(IBGDP-2023-01)。
文摘The squeezing deformation of surrounding rock is an important factor restricting the safe construction and long-term operation of tunnels when a tunnel passes through soft strata with high ground stress.Under such soft rock geological conditions,the large deformation of the surrounding rock can easily lead to the failure of supporting structures,including shotcrete cracks,spalling,and steel arch distortion.To improve the lining support performance during the large deformation of squeezed surrounding rock,this work selects aluminum foam with densities of 0.25 g/cm3,0.42 g/cm3 and 0.61 g/cm3 as the buffer layer material and carries out uniaxial confined compression tests.Through the evaluation and analysis of energy absorption and the comparison of the yield pressure of aluminum foam with those of other cushioning materials and yield pressure support systems,the strength,deformation and energy absorption of aluminum foam with a density of 0.25 g/cm3 meet the yield pressure performance requirements.The numerical model of the buffer layer yielding support system is then established via the finite element analysis software ABAQUS,and the influence of the buffer layer setting on the lining support is analyzed.Compared with the conventional support scheme,the addition of an aluminum foam buffer layer can reduce the stress and deformation of the primary support and secondary lining.The maximum and minimum principal stresses of the primary support are reduced by 13%and 15%,respectively.The maximum and minimum principal stresses of the secondary lining are reduced by 15%and 12%,respectively,and the displacement deformation of the secondary lining position is reduced by 15%.In summary,the application of aluminum foam buffer layer can reduce the stress and deformation of the primary support and secondary lining,improve the stress safety of the support and reduce the deformation of the support.
文摘1.Introduction As China’s first floating production platform in ultra-deepwater,the“Deep Sea No.1”energy station is a milestone in China’s deepwater resource utilization.The energy station is located in the LS17-2 gas field,150 km off the southeast coast of Hainan Island,China.It is a semi-submersible platform(Fig.1)with a displacement of 101 thousand tonnes and an operational draft of 35 to 40 m.The platform is permanently moored in 1422 m water by 16 chain-polyester-chain mooring lines in a 4×4 pattern,and six steel catenary risers(SCRs)are attached to the platform.It is the world’s first and only semi-submersible platform with the function of condensate storage,so it can be regarded as a floating production storage and offloading(FPSO)unit.With the ability to produce 3 billion m3 of natural gas each year(enough for over 10 million families),the Deep Sea No.1 energy station is a key step toward China’s energy independence.The LS17-2 gas field,where the Deep Sea No.1 energy station is located,was discovered in 2014.Plans for its development were made in 2015,followed by research and a preliminary design.Deep Sea No.1 went into operation on June 25,2021,and will operate onsite continuously without dry-docking for 30 years.
基金financially supported by the National Natural Science Foundation of China(Grant No.52078334)the National Key Research and Development Program of China(Grant No.2017YFC0805402)the Tianjin Research Innovation Project for Postgraduate Students(Grant No.2021YJSB141).
文摘The deformation caused by tunnel excavation is quite important for safety,especially when it is adjacent to the existing tunnel.Nevertheless,the investigation of deformation characteristics in overlapped curved shield tunneling remains inadequate.The analytical solution for calculating the deformation of the ground and existing tunnel induced by overlapped curved shield tunneling is derived by the Mirror theory,Mindlin solution and Euler-Bernoulli-Pasternak model,subsequently validated through both finite element simulation and field monitoring.It is determined that the overcutting plays a crucial role in the ground settlement resulting from curved shield tunneling compared to straight shield tunneling.The longitudinal settlement distribution can be categorized into five areas,with the area near the tunnel surface experiencing the most dramatic settlement changes.The deformation of the existing tunnel varies most significantly with turning radius compared to tunnel clearance and grouting pressure,especially when the turning radius is less than 30 times the tunnel diameter.The tunnel crown exhibits larger displacement than the tunnel bottom,resulting in a distinctive‘vertical egg'shape.Furthermore,an optimized overcutting mode is proposed,involving precise control of the extension speed and angular velocity of the overcutting cutter,which effectively mitigates ground deformation,ensuring the protection of the existing tunnel during the construction.
基金supported in part by the High-tech ship scientific research project of the Ministry of Industry and Information Technology of the People’s Republic of China,and the National Nature Science Foundation of China(Grant No.71671113)the Science and Technology Department of Shaanxi Province(No.2020GY-219)the Ministry of Education Collaborative Project of Production,Learning and Research(No.201901024016).
文摘Ship outfitting is a key process in shipbuilding.Efficient and high-quality ship outfitting is a top priority for modern shipyards.These activities are conducted at different stations of shipyards.The outfitting plan is one of the crucial issues in shipbuilding.In this paper,production scheduling and material ordering with endogenous uncertainty of the outfitting process are investigated.The uncertain factors in outfitting equipment production are usually decision-related,which leads to difficulties in addressing uncertainties in the outfitting production workshops before production is conducted according to plan.This uncertainty is regarded as endogenous uncertainty and can be treated as non-anticipativity constraints in the model.To address this problem,a stochastic two-stage programming model with endogenous uncertainty is established to optimize the outfitting job scheduling and raw material ordering process.A practical case of the shipyard of China Merchants Heavy Industry Co.,Ltd.is used to evaluate the performance of the proposed method.Satisfactory results are achieved at the lowest expected total cost as the complete kit rate of outfitting equipment is improved and emergency replenishment is reduced.
基金The National Key R&D Program Projects(Grant No.2022YFC2803601)the Natural Science Foundation of Shandong Province(Grant No.ZR2021YQ29)+1 种基金the Natural Science Foundation of Heilongjiang Province(Grant No.YQ2024E036)the Taishan Scholars Project(Grant No.tsqn202312317).
文摘Autonomous Underwater Vehicles(AUVs)are pivotal for deep-sea exploration and resource exploitation,yet their reliability in extreme underwater environments remains a critical barrier to widespread deployment.Through systematic analysis of 150 peer-reviewed studies employing mixed-methods research,this review yields three principal advancements to the reliability analysis of AUVs.First,based on the hierarchical functional division of AUVs into six subsystems(propulsion system,navigation system,communication system,power system,environmental detection system,and emergency system),this study systematically identifies the primary failure modes and potential failure causes of each subsystem,providing theoretical support for fault diagnosis and reliability optimization.Subsequently,a comprehensive review of AUV reliability analysis methods is conducted from three perspectives:analytical methods,simulated methods,and surrogate model methods.The applicability and limitations of each method are critically analyzed to offer insights into their suitability for engineering applications.Finally,the study highlights key challenges and research hotpots in AUV reliability analysis,including reliability analysis under limited data,AI-driven reliability analysis,and human reliability analysis.Furthermore,the potential of multi-sensor data fusion,edge computing,and advanced materials in enhancing AUV environmental adaptability and reliability is explored.
基金supported by the Ningbo Major Research and Development Plan Project(Grant No.2024Z135)the Natural Science Basic Research Program of Shaanxi Province(Grant No.2024JC-YBMS-322)+1 种基金China Postdoctoral Science Foundation(Grant No.2020M673492)National Natural Science Foundation of China(Grant No.51909219)。
文摘In this paper,a type of reinforcing structure for composite shell with single and through hole is presented.The experimental tests for the composite shells without hole,with single hole and reinforced structure,with through hole and reinforced structure subjected to hydrostatic pressure were carried out by the designed experimental test system.The mechanical responses of the composite shells under hydrostatic pressure are obtained by the high-speed camera and strain measurement.The results show that the entire deformation process of the shell can be divided into three:uniform compression,"buckling mode formation"and buckling.The"buckling mode formation"process is captured and reported for the first time.For the composite shell with single hole,the proposed reinforcing structure has a significant reinforcement effect on the shell and the buckling capacity of the shell is not weaker than the complete composite shell.For the composite shell with through hole,sealing effect can be achieved by the proposed reinforcing structure,but the buckling capacity of the shell after reinforcement can only reach 77%of the original buckling capacity.
基金supported by Southern Marine Science and Guangdong Laboratory(Zhuhai)(Grant No.SML2023SP229)。
文摘The maneuverability and stealth of aerial-aquatic vehicles(AAVs)is of significant importance for future integrated air-sea combat missions.To improve the maneuverability and stealth of AAVs near the water surface,this paper proposed a high-maneuverability skipping motion strategy for the tandem twin-rotor AAV,inspired by the motion behavior of the flying fish to avoid aquatic and aerial predators near the water surface.The novel tandem twin-rotor AAV was employed as the research subject and a strategybased ADRC control method for validation,comparing it with a strategy-based PID control method.The results indicate that both control methods enable the designed AAV to achieve high stealth and maneuverability near the water surface with robust control stability.The strategy-based ADRC control method exhibits a certain advantage in controlling height,pitch angle,and reducing impact force.This motion strategy will offer an inspiring approach for the practical application of AAVs to some extent.
基金supported by the National Natural Science Foundation of China under Grants 62001359 and 61901201by the Key Science and Technology Research Project of Henan Province under Grants 232102211059the Natural Science Basic Research Program of Shaanxi under Grants 2022JQ-658 and 2022JQ-621。
文摘The utilization of unmanned aerial vehicle(UAV) relays in cooperative communication has gained considerable attention in recent years.However,the current research is mostly based on fixed base stations and users,lacking sufficient exploration of scenarios where communication nodes are in motion.This paper presents a multi-destination vehicle communication system based on decode-and-forward(DF)UAV relays,where source and destination vehicles are moving and an internal eavesdropper intercepts messages from UAV.The closed-form expressions for system outage probability and secrecy outage probability are derived to analyze the reliability and security of the system.Furthermore,the impact of the UAV's position,signal transmission power,and system time allocation ratio on the system's performance are also analyzed.The numerical simulation results validate the accuracy of the derived formulas and confirm the correctness of the analysis.The appropriate time allocation ratio significantly enhances the security performance of system under various environmental conditions.
文摘Based on inspection data,the authors analyze and summarize the main types and distribution characteristics of tunnel structural defects.These defects are classified into three types:surface defects,internal defects,and defects behind the structure.To address the need for rapid detection of different defect types,the current state of rapid detection technologies and equipment,both domestically and internationally,is systematically reviewed.The research reveals that surface defect detection technologies and equipment have developed rapidly in recent years.Notably,the integration of machine vision and laser scanning technologies have significantly improved detection efficiency and accuracy,achieving crack detection precision of up to 0.1 mm.However,the non-contact rapid detection of internal and behind-the-structure defects remains constrained by hardware limitations,with traditional detection remaining dominant.Nevertheless,phased array radar,ultrasonic,and acoustic vibration detection technologies have become research hotspots in recent years,offering promising directions for detecting these challenging defect types.Additionally,the application of multisensor fusion technology in rapid detection equipment has further enhanced detection capabilities.Devices such as cameras,3D laser scanners,infrared thermal imagers,and radar demonstrate significant advantages in rapid detection.Future research in tunnel inspection should prioritize breakthroughs in rapid detection technologies for internal and behind-the-structure defects.Efforts should also focus on developing multifunctional integrated detection vehicles that can simultaneously inspect both surface and internal structures.Furthermore,progress in fully automated,intelligent systems with precise defect identification and real-time reporting will be essential to significantly improve the efficiency and accuracy of tunnel inspection.
基金supported by the Open Research Fund of Key Laboratory of Geological Hazards on Three Gorges Reservoir Area(China Three Gorges University),Ministry of Education(No.2022KDZ03)the Science and Technology Projects of Yunnan Provincial Science and Technology Department(No.202401AT070328)+1 种基金the Young talents project of“Xingdian Talent Support Program”in Yunnan Province(No.YNWR-QNBJ-2020-019)the Fund Project of China Academy of Railway Sciences Co.,Ltd.(No.2021YJ178)。
文摘0 INTRODUCTION In recent years,modern railways have been actively under construction in the complex mountainous area of Southwest China.However,rockfall poses a significant threat to both construction and operation phases of railway projects(Yan et al.,2023;Chen et al.,2022;Fanos and Pradhan,2018).
文摘The advancement of 6G wireless communication technology has facilitated the integration of Vehicular Ad-hoc Networks(VANETs).However,the messages transmitted over the public channel in the open and dynamic VANETs are vulnerable to malicious attacks.Although numerous researchers have proposed authentication schemes to enhance the security of Vehicle-to-Vehicle(V2V)communication,most existing methodologies face two significant challenges:(1)the majority of the schemes are not lightweight enough to support realtime message interaction among vehicles;(2)the sensitive information like identity and position is at risk of being compromised.To tackle these issues,we propose a lightweight dual authentication protocol for V2V communication based on Physical Unclonable Function(PUF).The proposed scheme accomplishes dual authentication between vehicles by the combination of Zero-Knowledge Proof(ZKP)and MASK function.The security analysis proves that our scheme provides both anonymous authentication and information unlinkability.Additionally,the performance analysis demonstrates that the computation overhead of our scheme is approximately reduced 23.4% compared to the state-of-the-art schemes.The practical simulation conducted in a 6G network environment demonstrates the feasibility of 6G-based VANETs and their potential for future advancements.
基金supported by the National Natural Science Foundation of China(Grant Nos.42277165,41920104007)the Hubei Natural Science Foundation(Grant No.2023AFD217).
文摘The safety of the initial support during the construction of inclined shafts in tunnels traversing through high-hydraulic-pressure surrounding rocks is paramount.This study examines a high-hydraulic-pressure inclined shaft of a tunnel in Western Sichuan Province to analyze the damage characteristics of the initial support and propose a radial drainage and decompression treatment method.Field monitoring was conducted to assess the load and deformation of the initial support structure,and on-site investigations identified the distribution of cracked areas.In addition,numerical simulations were performed to evaluate the force and deformation characteristics of the initial support structure,which were then compared with field observations for validation.The variations in the lateral pressure coefficient and water pressure were evaluated.The results revealed that damage was primarily concentrated in the shoulder,spring line,and knee areas,with the bending moment at the knee increasing by up to 66.9%.The application of the radial drainage and decompression treatment method effectively reduced water pressure loads on the initial support.Post-treatment analysis indicated significant reductions in axial force and bending moment,enhancing structural stability.These findings provide valuable insights for improving the safety and durability of initial support systems in inclined shafts of high-hydraulicpressure railroad tunnels.
文摘This paper provides a comprehensive review of various experimental methods used to study carbon corrosion in automotive polymer exchange membrane fuel cells.Quantifying the extent of carbon corrosion is essential for advancing the technology and implementing effective mitigation strategies.While studying degradation events directly within a real-world fuel cell vehicle offers the most reliable insights,the high costs and time demands make it necessary to develop specialised experimental techniques that provide high-resolution data more efficiently and cost-effectively.This review explores the various experimental approaches utilised in automotive application induced carbon corrosion studies globally,including load profiles,test setups,break-in procedures,and cell recovery protocols.In this paper,emphasis is placed on the standardised procedures proposed by leading institutions worldwide,accompanied by critical discussions on these protocols.Furthermore,the paper highlights modified or innovative procedures developed by smaller institutions,universities,and individual researchers,thereby offering a comprehensive overview essential for carbon corrosion analysis.The review also discusses the fundamental principles,benefits,and limitations of various procedures,offering guidance on selecting the most appropriate approach for a given study.Lastly,it addresses the limitations within the current body of literature and outlines potential future prospects.
文摘Pre-injection is a technique that involves injecting grout materials into the ground prior to excavation,with the aim of stabilizing the surrounding rock mass.This paper introduces an analytical closed-form model for determining the ground reaction curve of tunnels in rock masses exhibiting elastic-brittleplastic behavior and adhering to the Mohr-Coulomb failure criterion.The model incorporates the reinforced region created by the pre-injection method.When the rock mass is reinforced through preinjection,plastic regions can form independently in both the natural and injected rock masses.This leads to six distinct modes of the problem.The analytical model presented in this paper considers three possible scenarios for the development of plastic regions.Each scenario comprises four stages,with each stage representing a different mode of the problem.While injecting the rock mass can enhance its strength and stiffness,it may also increase the brittleness of the injected rock mass and create stress concentrations within it,particularly when brittle grouts are used.As a result,this can elevate the risk of rockburst due to unstable failure.The results obtained from the model demonstrate that ductile grout performs exceptionally well in controlling tunnel convergence in rock masses,as it accommodates deformation without sudden failure,even in squeezing rock mass conditions.Conversely,the use of brittle grouts should be approached with caution,particularly in squeezing rock masses,due to their susceptibility to rockburst incidents.
基金supported by the National Natural Science Foundation of China(Grant No.42377191,42072300)“The 14th Five Year Plan”Hubei Provincial advantaged characteristic disciplines(groups)project of Wuhan University of Science and Technology(Grant No.2023A0303).
文摘The stability of the tunnel portal slope is crucial for ensuring safe tunnel construction.Thus,a sound stability evaluation is of significance.Given the unique geological characteristics of tunnel portal slopes,it is necessary to establish a specific evaluation indicator system that differs from those used for ordinary slopes.Based on the unascertained measure method,uncertainties in the indicator are addressed by introducing the left and right half cloud asymmetric cloud model to optimize the linear membership function.The subjectivity of confidence criterion level identification is also improved by using the Euclidean distance method.Thus,a stability evaluation model for the tunnel portal slope is established based on the improved unascertained measure method.Finally,using the collected tunnel portal slope data,the results of four evaluation methods are compared with the safety factor levels.The evaluation methods include the traditional unascertained measure method,the method improved by using the left and right half cloud asymmetric cloud model,the method improved by using the Euclidean distance method,and the method improved by using both the left and right half cloud asymmetric cloud model and the Euclidean distance method.The results show that the accuracy rates of these four methods are 50%,55%,85%,and 90%,respectively.Among them,the joint improvement method has the slightest deviation,with only one level,while the other three methods had deviations of two levels.This result verifies the stability and effectiveness of the joint improvement method,providing a reference for tunnel portal slope stability evaluation.
基金This work was supported by the National Natural Science Foundation of China(Grant No.12272141)The financial support is gratefully acknowledged.
文摘The transformation from multibody models to lumped-parameter models is a crucial aspect of vehicle dynamics research.The velocity transformation method is adopted in this research,and the suspension multibody model is described using only one degree of freedom.It is found that the equivalent mass of the system is time-dependent during the simulation process,as observed in numerical simulations.Further symbolic calculations are conducted to derive the analytical form of the equivalent mass,and the results show that once the static parameters are determined,the equivalent mass of the suspension system is determined solely by the vertical position of the suspension upright,which reveals the kinematics characteristic of the equivalent mass of the suspension system.It is found that the equivalent mass experiences smaller changes when the suspension is compressed from the middle position,but larger changes when the suspension is extended.Furthermore,by comparing the multibody model,the lumped-parameter model with static mass,and the proposed lumped-parameter model considering the kinematics characteristic of the equivalent unsprung mass,the proposed model produces simulation results that more closely match the original multibody model than the model with static mass.The improvements in accuracy can be up to 20%under certain evaluation metrics.
