The reconstruction of the temporomandibular joint presents a multifaceted clinical challenge in the realm of head and neck surgery,underscored by its relatively infrequent occurrence and the lack of comprehensive clin...The reconstruction of the temporomandibular joint presents a multifaceted clinical challenge in the realm of head and neck surgery,underscored by its relatively infrequent occurrence and the lack of comprehensive clinical guidelines.This review aims to elucidate the available approaches for TMJ reconstruction,with a particular emphasis on recent groundbreaking advancements.The current spectrum of TMJ reconstruction integrates diverse surgical techniques,such as costochondral grafting,coronoid process grafting,revascularized fibula transfer,transport distraction osteogenesis,and alloplastic TMJ replacement.Despite the available options,a singular,universally accepted‘gold standard’for reconstructive techniques or materials remains elusive in this field.Our review comprehensively summarizes the current available methods of TMJ reconstruction,focusing on both autologous and alloplastic prostheses.It delves into the differences of each surgical technique and outlines the implications of recent technological advances,such as 3D printing,which hold the promise of enhancing surgical precision and patient outcomes.This evolutionary progress aims not only to improve the immediate results of reconstruction but also to ensure the long-term health and functionality of the TMJ,thereby improving the quality of life for patients with end-stage TMJ disorders.展开更多
We present a grid-growth method to reconstruct 3D rock joints with arbitrary joint roughness and persistence.In the first step of this workflow,the joint model is divided into uniform grids.Then by adjusting the posit...We present a grid-growth method to reconstruct 3D rock joints with arbitrary joint roughness and persistence.In the first step of this workflow,the joint model is divided into uniform grids.Then by adjusting the positions of the grids,the joint morphology can be modified to construct models with desired joint roughness and persistence.Accordingly,numerous joint models with different joint roughness and persistence were built.The effects of relevant parameters(such as the number,height,slope of asperities,and the number,area of rock bridges)on the joint roughness coefficient(JRC)and joint persistence were investigated.Finally,an artificially split joint was reconstructed using the method,and the method's accuracy was evaluated by comparing the JRC of the models with that of the artificially split joint.The results showed that the proposed method can effectively control the JRC of joint models by adjusting the number,height,and slope of asperities.The method can also modify the joint persistence of joint models by adjusting the number and area of rock bridges.Additionally,the JRC of models obtained by our method agrees with that of the artificially split surface.Overall,the method demonstrated high accuracy for 3D rock joint reconstruction.展开更多
Non-seismically designed(NSD)beam-column joints are susceptible to joint shear failure under seismic loads.Although significant research is available on the seismic behavior of such joints of planar frames,the informa...Non-seismically designed(NSD)beam-column joints are susceptible to joint shear failure under seismic loads.Although significant research is available on the seismic behavior of such joints of planar frames,the information on the seismic behavior of joints of space frames(3D joints)is insufficient.The 3D joints are subjected to bi-directional excitation,which results in an interaction between the shear strength obtained for the joint in the two orthogonal directions separately.The bi-directional seismic behavior of corner reinforced concrete(RC)joints is the focus of this study.First,a detailed finite element(FE)model using the FE software Abaqus,is developed and validated using the test results from the literature.The validated modeling procedure is used to conduct a parametric study to investigate the influence of different parameters such as concrete strength,dimensions of main and transverse beams framing into the joint,presence or absence of a slab,axial load ratio and loading direction on the seismic behavior of joints.By subjecting the models to different combinations of loads on the beams along perpendicular directions,the interaction of the joint shear strength in two orthogonal directions is studied.The comparison of the interaction curves of the joints obtained from the numerical study with a quadratic(circular)interaction curve indicates that in a majority of cases,the quadratic interaction model can represent the strength interaction diagrams of RC beam to column connections with governing joint shear failure reasonably well.展开更多
Purpose–The bridge expansion joint(BEJ)is a key device for accommodating spatial displacement at the beam end,and for providing vertical support for running trains passing over the gap between the main bridge and the...Purpose–The bridge expansion joint(BEJ)is a key device for accommodating spatial displacement at the beam end,and for providing vertical support for running trains passing over the gap between the main bridge and the approach bridge.For long-span railway bridges,it must also be coordinated with rail expansion joint(REJ),which is necessary to accommodate the expansion and contraction of,and reducing longitudinal stress in,the rails.The main aim of this study is to present analysis of recent developments in the research and application of BEJs in high-speed railway(HSR)long-span bridges in China,and to propose a performance-based integral design method for BEJs used with REJs,from both theoretical and engineering perspectives.Design/methodology/approach–The study first presents a summary on the application and maintenance of BEJs in HSR long-span bridges in China representing an overview of their state of development.Results of a survey of typical BEJ faults were analyzed,and field testing was conducted on a railway cable-stayed bridge in order to obtain information on the major mechanical characteristics of its BEJ under train load.Based on the above,a performance-based integral design method for BEJs with maximum expansion range 1600 mm(±800 mm),was proposed,covering all stages from overall conceptual design to consideration of detailed structural design issues.The performance of the novel BEJ design thus derived was then verified via theoretical analysis under different scenarios,full-scale model testing,and field testing and commissioning.Findings–Two major types of BEJs,deck-type and through-type,are used in HSR long-span bridges in China.Typical BEJ faults were found to mainly include skewness of steel sleepers at the bridge gap,abnormally large longitudinal frictional resistance,and flexural deformation of the scissor mechanisms.These faults influence BEJ functioning,and thus adversely affect track quality and train running performance at the beam end.Due to their simple and integral structure,deck-type BEJs with expansion range 1200 mm(±600 mm)or less have been favored as a solution offering improved operational conditions,and have emerged as a standard design.However,when the expansion range exceeds the above-mentioned value,special design work becomes necessary.Therefore,based on engineering practice,a performance-based integral design method for BEJs used with REJs was proposed,taking into account four major categories of performance requirements,i.e.,mechanical characteristics,train running quality,durability and insulation performance.Overall BEJ design must mainly consider component strength and the overall stiffness of BEJ;the latter factor in particular has a decisive influence on train running performance at the beam end.Detailed BEJ structural design must stress minimization of the frictional resistance of its sliding surface.The static and dynamic performance of the newlydesigned BEJ with expansion range 1600 mm have been confirmed to be satisfactory,via numerical simulation,full-scale model testing,and field testing and commissioning.Originality/value–This research provides a broad overview of the status of BEJs with large expansion range in HSR long-span bridges in China,along with novel insights into their design.展开更多
The clinical treatment of severe trauma withsternoclavicular joint injury is challenging,primarilydue to the irregular shape of the bones surrounding thesternoclavicular joint,as well as the posterior clavicle beingcl...The clinical treatment of severe trauma withsternoclavicular joint injury is challenging,primarilydue to the irregular shape of the bones surrounding thesternoclavicular joint,as well as the posterior clavicle beingclose to the aorta and mediastinal organs.^([1])These patientsnot only suffer direct injuries to the sternoclavicularjoint,but also frequently experience severe injuries toother body parts.The systemic physiological disordersand multi-organ dysfunction caused by severe traumaincrease the surgery di?culty and mortality risk.^([2])展开更多
Rock joints always have a smaller strength,and it plays an important influence on the overall strength of rock mass.The mechanical behavior of rock joints is mainly governed by the surface topography,normal stress,and...Rock joints always have a smaller strength,and it plays an important influence on the overall strength of rock mass.The mechanical behavior of rock joints is mainly governed by the surface topography,normal stress,and failure degree.In this study,a series of direct shear tests for four different rough rock joints under five normal stresses was carried out.The shear and normal stiffnesses were first determined,and the shear shrinkage effect was represented by a shear-normal coupling coefficient.Assuming that the strength of the joint is composed of frictional and cohesive parts,the evolutions of cohesion,friction angle with joint roughness coefficient(JRC),and plastic shear displacement are obtained.The dilatancy behavior is described by the dilation angle,which is considered a function of JRC,plastic shear displacement,and normal stress.A cohesive-frictional elastoplastic constitutive model is hence proposed.The theoretical curves under constant normal stress conditions of the proposed model are in good agreement with the experimental results.The shear behaviors under constant normal stiffness and constant normal displacement conditions can be predicted using the new constitutive model.展开更多
The joint roughness coefficient(JRC) is one of the key parameters for evaluating the shear strength of rock joints.Because of the scale effect in the JRC,reliable JRC values are of great importance for most rock engin...The joint roughness coefficient(JRC) is one of the key parameters for evaluating the shear strength of rock joints.Because of the scale effect in the JRC,reliable JRC values are of great importance for most rock engineering projects.During the collection process of JRC samples,the redundancy or insufficiency of representative rock joint surface topography(RJST) information in serial length JRC samples is the essential reason that affects the reliability of the scale effect results.Therefore,this paper proposes an adaptive sampling method,in which we use the entropy consistency measure Q(a) to evaluate the consistency of the joint morphology information contained in adjacent JRC samples.Then the sampling interval is automatically adjusted according to the threshold Q(at) of the entropy consistency measure to ensure that the degree of change of RJST information between JRC samples is the same,and ultimately makes the representative RJST information in the collected JRC samples more balanced.The application results of actual cases show that the proposed method can obtain the scale effect in the JRC efficiently and reliably.展开更多
The configuration of underground powerhouses is crucial in pumped-storage hydropower projects,which play a vital role in maintaining grid stability,facilitating the integration of renewable energy sources,and managing...The configuration of underground powerhouses is crucial in pumped-storage hydropower projects,which play a vital role in maintaining grid stability,facilitating the integration of renewable energy sources,and managing flood risks.However,geotechnical challenges,such as complex joint orientations,anisotropy in in-situ stress,and rock damage caused by excavation,require thorough stability assessments.This research employs the ubiquitous anisotropic joint model within FLAC3D to investigate the effects of joint dip angle,joint dip direction,and the alignment of in-situ stress on the stability of surrounding rock formations.The key parameters analyzed include joint cohesion,friction angle,and the magnitude of in-situ stress.The numerical results indicate that deformation is minimized when the axis of the powerhouse is aligned with the major principal stress.Furthermore,joint dip angles between 65°and 70°lead to a 50%reduction in both displacement and plastic zone volume.Additionally,angles less than 40°between the joint dip direction and the powerhouse axis enhance stability.These findings provide practical recommendations for optimizing the orientation of powerhouses in geomechanical contexts similar to those characterized by foliated sericite phyllite with moderate joint persistence.展开更多
The shear performance of bolts plays a crucial role in controlling rock mass stability,and the roughness of the joint surface is one of the main factors affecting the mechanical properties of anchored joints.The 2nd g...The shear performance of bolts plays a crucial role in controlling rock mass stability,and the roughness of the joint surface is one of the main factors affecting the mechanical properties of anchored joints.The 2nd generation of negative Poisson ratio(2G-NPR)bolt is a new independently developed material characterized by high strength and toughness.However,the influence of joint surface roughness on its anchorage shear performance remains unexplored.This study involves preparing regular saw-tooth jointed rock masses and conducting laboratory shear comparison tests on unbolted samples,2G-NPR bolts,and Q235 steel anchors.A three-dimensional finite element method,developed by the author,was employed for numerical simulations to analyze the influence of saw-tooth angles on the shear resistance of anchored bolts.The findings show that the anchorage of bolts enhances the shear strength and deformation of saw-tooth rock joints.The 2G-NPR bolts demonstrate superior performance in shear strength and deformation enhancement compared to Q235 steel anchors,including improved toughening and crack-arresting effects.Furthermore,the improvement of the shear strength and displacement of the bolt decreases with the increase of the joint saw-tooth angle.These findings provide a valuable test basis for the engineering application of 2G-NPR bolts in rock mass stabilization.展开更多
Temporomandibular joint(TMJ)disc displacement is one of the most significant subtypes of temporomandibular joint disorders,but its etiology and mechanism are poorly understood.In this study,we elucidated the mechanism...Temporomandibular joint(TMJ)disc displacement is one of the most significant subtypes of temporomandibular joint disorders,but its etiology and mechanism are poorly understood.In this study,we elucidated the mechanisms by which destruction of inflamed collagen fibrils induces alterations in the mechanical properties and positioning of the TMJ disc.By constructing a rat model of TMJ arthritis,we observed anteriorly dislocated TMJ discs with aggravated deformity in vivo from five weeks to six months after a local injection of Freund’s complete adjuvant.By mimicking inflammatory conditions with interleukin-1 beta in vitro,we observed enhanced expression of collagen-synthesis markers in primary TMJ disc cells cultured in a conventional two-dimensional environment.In contrast,three-dimensional(3D)-cultivated disc cell sheets demonstrated the disordered assembly of inflamed collagen fibrils,inappropriate arrangement,and decreased Young’s modulus.Mechanistically,inflammation-related activation of the nuclear factor kappa-B(NF-κB)pathway occurs during the progression of TMJ arthritis.NF-κB inhibition reduced the collagen fibril destruction in the inflamed disc cell sheets in vitro,and early NF-κB blockade alleviated collagen degeneration and dislocation of the TMJ discs in vivo.Therefore,the NF-κB pathway participates in the collagen remodeling in inflamed TMJ discs,offering a potential therapeutic target for disc displacement.展开更多
Purpose–This study aims to investigate the fatigue behavior and failure modes of bolted lap joints using Modified Tensile Specimens(MTS)under various cyclic load conditions.Emphasis is placed on identifying the relat...Purpose–This study aims to investigate the fatigue behavior and failure modes of bolted lap joints using Modified Tensile Specimens(MTS)under various cyclic load conditions.Emphasis is placed on identifying the relationship between load amplitude,fatigue life,and damage progression in low-carbon steel assemblies.Design/methodology/approach–An experimental approach was adopted using MTS specimens fabricated from St 1203 cold-rolled steel,joined with Grade 8.8 M4 bolts.Cyclic fatigue tests were conducted under zerobased loading at seven distinct force levels.Fracture surfaces were visually analyzed to identify dominant failure mechanisms.Findings–The results revealed a strong inverse correlation between applied cyclic load and fatigue life.Three distinct failure modes were identified:bolt shear at high loads(5.4 kN),interface cracking and slippage at moderate loads(4.9–5.1 kN),and plate tearing or stable fatigue behavior at lower loads(54.1 kN).The results highlight a progressive transition in failure mechanisms,from bolt shear at high loads to plate tearing and interface cracking at lower loads,providing essential insights for fatigue-resistant bolted joint design.Originality/value–This study offers original insights into the fatigue behavior of bolted lap joints using MTS,a relatively underexplored configuration in fatigue assessment.By experimentally evaluating failure modes under varied cyclic load levels,the authors uncover critical transitions in damage mechanisms—from bolt shear to interface cracking and plate tearing—depending on the applied load.Unlike many existing studies focused on numerical modeling or bonded joints alone,this work provides empirical data rooted in real-world fastening conditions using cold-rolled low-carbon steel.展开更多
The joint roughness coefficient(JRC)is a key parameter in the assessment of mechanical properties and the stability of rock masses.This paper presents a novel approach to JRC evaluation using a genetic algorithm-optim...The joint roughness coefficient(JRC)is a key parameter in the assessment of mechanical properties and the stability of rock masses.This paper presents a novel approach to JRC evaluation using a genetic algorithm-optimized backpropagation(GA-BP)neural network.Conventional JRC evaluations have typically depended on two-dimensional(2D)and three-dimensional(3D)parameter calculation methods,which fail to fully capture the nonlinear relationship between the complex surface morphology of joints and their roughness.Our analysis from shear tests on eight different joint types revealed that the strength and failure characteristics of the joints not only exhibit directional dependence but also positively correlate with surface dip angles,heights,and back slope morphological features.Subsequently,five simple statistical parameters,i.e.average dip angle,median dip angle,average height,height coefficient of variation,and back slope feature value(K),were utilized to quantify these characteristics.For the prediction of JRC,we compiled and analyzed 105 datasets,each containing these five statistical parameters and their corresponding JRC values.A GA-BP neural network model was then constructed using this dataset,with the five morphological characteristic statistics serving as inputs and the JRC values as outputs.A comparative analysis was performed between the GA-BP neural network model,the statistical parameter method,and the fractal parameter method.This analysis confirmed that our proposed method offers higher accuracy in evaluating the roughness coefficient and shear strength of joints.展开更多
The scale effect on shear strength of rock joints is well-documented.However,whether scale effects are negative,positive,or even exist or not is still controversial.Joint roughness significantly influences the shear s...The scale effect on shear strength of rock joints is well-documented.However,whether scale effects are negative,positive,or even exist or not is still controversial.Joint roughness significantly influences the shear strength of rock joints.Compared to the shear tests,using the joint roughness coefficient(JRC)and its roughness parameters offers a more convenient method for describing the scale effect on shear strength.However,it is crucial to understand that the scale effect mechanisms of JRC are distinct from those of shear strength.Therefore,this paper aims to clarify these distinct mechanisms.By digitally extracting roughness parameters from granite samples,it is found that the scale effect of roughness parameters mainly comes from the sampling methods and the geometric characteristics of parameters.Furthermore,a full data sampling method considering heterogeneity is proposed to obtain more representative roughness parameters.To reveal the scale effect mechanisms of shear strength,Gaussian filtering is firstly used to separate the waviness and unevenness components of roughness,facilitating a deeper understanding of the geometric characteristics of roughness.It is suggested that the wavelength of the waviness component can reflect the scale effect on shear strength.Secondly,numerical simulations of ideal artificial joint models are conducted to validate that the wavelength of the waviness component serves as the dividing point between positive and negative scale effects.The mechanical mechanisms of positive and negative scale effects are also interpreted.Finally,these mechanisms successfully elucidate the occurrence patterns of the scale effect on natural joint profiles.展开更多
Human-robot safety is an important topic in wearable robotics,especially in supernumerary robotic limbs(SRLs).The proposal of flexible joint improves human-robot safety strategy,which allows physical contact between h...Human-robot safety is an important topic in wearable robotics,especially in supernumerary robotic limbs(SRLs).The proposal of flexible joint improves human-robot safety strategy,which allows physical contact between human and robots,rather than strictly limiting the human-robot motion.However,most researchers focus on the variable stiffness features of flexible joints,but few evaluate the performance of the flexible joint in the human-robot collision.Therefore,the performance of two typical flexible joints,including the series elastic joint(SEJ)and the passive variable stiffness joint(PVSJ),are compared through dynamic collision experiments.The results demonstrate that the SEJ absorbs 40.7%-58.7%of the collision force and 34.2%-45.2%of the collision torque in the driven-torque below 4 N·m and driven-speed of 3-7(°)/s,which is more stable than PVSJ.In addition,the stiffness error of SEJ is measured at 5.1%,significantly lower than the 23.04%measured in the PVSJ.The huge stiffness error of PVSJ leads to its unreliability in buffering collision.Furthermore,we analyze results and confirm that SEJ has a more stable human-robot safety performance in buffering dynamic collision.Consequently,the SEJ is suitable in SRLs for human-robot safety in our scenario.展开更多
Semantic secure communication is an emerging field that combines the principles of source-channel coding with the need for secure data transmission.It is of great significance in modern communications to protect the c...Semantic secure communication is an emerging field that combines the principles of source-channel coding with the need for secure data transmission.It is of great significance in modern communications to protect the confidentiality and privacy of sensitive information and prevent information leaks and malicious attacks.This paper presents a novel approach to semantic secure communication through the utilization of joint source-channel coding,which is based on the design of an automated joint source-channel coding algorithm and an encryption and decryption algorithm based on semantic security.The traditional and state-of-the-art joint source-channel coding algorithms are selected as two baselines for different comparison purposes.Experimental results demonstrate that our proposed algorithm outperforms the first baseline algorithm,the traditional source-channel coding,by 61.21%in efficiency under identical channel conditions(SNR=15 dB).In security,our proposed method can resist 2 more types of attacks compared to the two baselines,exhibiting nearly no increases in time consumption and error rate compared to the state-of-the-art joint source-channel coding algorithm while the secure semantic communication is supported.展开更多
Young's modulus and Poisson's ratio are crucial parameters for reservoir characterization and rock brittleness evaluation.Conventional methods often rely on indirect computation or approximations of the Zoeppr...Young's modulus and Poisson's ratio are crucial parameters for reservoir characterization and rock brittleness evaluation.Conventional methods often rely on indirect computation or approximations of the Zoeppritz equations to estimate Young's modulus,which can introduce cumulative errors and reduce the accuracy of inversion results.To address these issues,this paper introduces the analytical solution of the Zoeppritz equation into the inversion process.The equation is re-derived and expressed in terms of Young's modulus,Poisson's ratio,and density.Within the Bayesian framework,we construct an objective function for the joint inversion of PP and PS waves.Traditional gradient-based algorithms often suffer from low precision and the computational complexity.In this study,we address limitations of conventional approaches related to low precision and complicated code by using Circle chaotic mapping,Levy flights,and Gaussian mutation to optimize the quantum particle swarm optimization(QPSO),named improved quantum particle swarm optimization(IQPSO).The IQPSO demonstrates superior global optimization capabilities.We test the proposed inversion method with both synthetic and field data.The test results demonstrate the proposed method's feasibility and effectiveness,indicating an improvement in inversion accuracy over traditional methods.展开更多
To map the rock joints in the underground rock mass,a method was proposed to semiautomatically detect the rock joints from borehole imaging logs using a deep learning algorithm.First,450 images containing rock joints ...To map the rock joints in the underground rock mass,a method was proposed to semiautomatically detect the rock joints from borehole imaging logs using a deep learning algorithm.First,450 images containing rock joints were selected from borehole ZKZ01 in the Rumei hydropower station.These images were labeled to establish ground truth which was subdivided into training,validation,and testing data.Second,the YOLO v2 model with optimal parameter settings was constructed.Third,the training and validation data were used for model training,while the test data was used to generate the precision-recall curve for prediction evaluation.Fourth,the trained model was applied to a new borehole ZKZ02 to verify the feasibility of the model.There were 12 rock joints detected from the selected images in borehole ZKZ02 and four geometric parameters for each rock joint were determined by sinusoidal curve fitting.The average precision of the trained model reached 0.87.展开更多
Waterproof performance of gaskets between segments is the focus of shield tunnels.This paper proposed an analytical method for determining seepage characteristics at tunnel-gasketed joints based on the hydraulic fract...Waterproof performance of gaskets between segments is the focus of shield tunnels.This paper proposed an analytical method for determining seepage characteristics at tunnel-gasketed joints based on the hydraulic fracturing theories.First,the mathematical model was established,and the seepage governing equation and boundary conditions were obtained.Second,three dimensionless parameters were introduced for simplifying the expressions,and the seepage governing equations were normalized.Third,analytical expressions were derived for the interface opening and liquid pressure.Moreover,the influencing factors of seepage process at the gasketed interface were analyzed.Parametric analyses revealed that,in the normalized criterion of liquid viscosity,the liquid tip coordinate was influenced by the degree of negative pressure in the liquid lag region,which was related to the initial contact stress.The coordinate of the liquid tip affected the liquid pressure distribution and the interface opening,which were analyzed under different liquid tip coordinate conditions.Finally,under two limit states,comparative analysis showed that the results of the variation trend of the proposed method agree well with those of previous research.Overall,the proposed analytical method provides a novel solution for the design of the waterproof in shield tunnels.展开更多
A conceptual model of intermittent joints is introduced to the cyclic shear test in the laboratory to explore the effects of loading parameters on its shear behavior under cyclic shear loading.The results show that th...A conceptual model of intermittent joints is introduced to the cyclic shear test in the laboratory to explore the effects of loading parameters on its shear behavior under cyclic shear loading.The results show that the loading parameters(initial normal stress,normal stiffness,and shear velocity)determine propagation paths of the wing and secondary cracks in rock bridges during the initial shear cycle,creating different morphologies of macroscopic step-path rupture surfaces and asperities on them.The differences in stress state and rupture surface induce different cyclic shear responses.It shows that high initial normal stress accelerates asperity degradation,raises shear resistance,and promotes compression of intermittent joints.In addition,high normal stiffness provides higher normal stress and shear resistance during the initial cycles and inhibits the dilation and compression of intermittent joints.High shear velocity results in a higher shear resistance,greater dilation,and greater compression.Finally,shear strength is most sensitive to initial normal stress,followed by shear velocity and normal stiffness.Moreover,average dilation angle is most sensitive to initial normal stress,followed by normal stiffness and shear velocity.During the shear cycles,frictional coefficient is affected by asperity degradation,backfilling of rock debris,and frictional area,exhibiting a non-monotonic behavior.展开更多
Joint roughness coefficient(JRC)is the most commonly used parameter for quantifying surface roughness of rock discontinuities in practice.The system composed of multiple roughness statistical parameters to measure JRC...Joint roughness coefficient(JRC)is the most commonly used parameter for quantifying surface roughness of rock discontinuities in practice.The system composed of multiple roughness statistical parameters to measure JRC is a nonlinear system with a lot of overlapping information.In this paper,a dataset of eight roughness statistical parameters covering 112 digital joints is established.Then,the principal component analysis method is introduced to extract the significant information,which solves the information overlap problem of roughness characterization.Based on the two principal components of extracted features,the white shark optimizer algorithm was introduced to optimize the extreme gradient boosting model,and a new machine learning(ML)prediction model was established.The prediction accuracy of the new model and the other 17 models was measured using statistical metrics.The results show that the prediction result of the new model is more consistent with the real JRC value,with higher recognition accuracy and generalization ability.展开更多
基金supported by NSFC(82370932)Research and Develop Program of West China Hospital of Stomatology Sichuan University(RD-03-202102,LCYJ2019-20)Natural Science Foundation of Sichuan Province(2023NSFSC1512,2024NSFSC1588)。
文摘The reconstruction of the temporomandibular joint presents a multifaceted clinical challenge in the realm of head and neck surgery,underscored by its relatively infrequent occurrence and the lack of comprehensive clinical guidelines.This review aims to elucidate the available approaches for TMJ reconstruction,with a particular emphasis on recent groundbreaking advancements.The current spectrum of TMJ reconstruction integrates diverse surgical techniques,such as costochondral grafting,coronoid process grafting,revascularized fibula transfer,transport distraction osteogenesis,and alloplastic TMJ replacement.Despite the available options,a singular,universally accepted‘gold standard’for reconstructive techniques or materials remains elusive in this field.Our review comprehensively summarizes the current available methods of TMJ reconstruction,focusing on both autologous and alloplastic prostheses.It delves into the differences of each surgical technique and outlines the implications of recent technological advances,such as 3D printing,which hold the promise of enhancing surgical precision and patient outcomes.This evolutionary progress aims not only to improve the immediate results of reconstruction but also to ensure the long-term health and functionality of the TMJ,thereby improving the quality of life for patients with end-stage TMJ disorders.
基金supported by the National Natural Science Foundation of China(Nos.12172019 and 42477210).
文摘We present a grid-growth method to reconstruct 3D rock joints with arbitrary joint roughness and persistence.In the first step of this workflow,the joint model is divided into uniform grids.Then by adjusting the positions of the grids,the joint morphology can be modified to construct models with desired joint roughness and persistence.Accordingly,numerous joint models with different joint roughness and persistence were built.The effects of relevant parameters(such as the number,height,slope of asperities,and the number,area of rock bridges)on the joint roughness coefficient(JRC)and joint persistence were investigated.Finally,an artificially split joint was reconstructed using the method,and the method's accuracy was evaluated by comparing the JRC of the models with that of the artificially split joint.The results showed that the proposed method can effectively control the JRC of joint models by adjusting the number,height,and slope of asperities.The method can also modify the joint persistence of joint models by adjusting the number and area of rock bridges.Additionally,the JRC of models obtained by our method agrees with that of the artificially split surface.Overall,the method demonstrated high accuracy for 3D rock joint reconstruction.
文摘Non-seismically designed(NSD)beam-column joints are susceptible to joint shear failure under seismic loads.Although significant research is available on the seismic behavior of such joints of planar frames,the information on the seismic behavior of joints of space frames(3D joints)is insufficient.The 3D joints are subjected to bi-directional excitation,which results in an interaction between the shear strength obtained for the joint in the two orthogonal directions separately.The bi-directional seismic behavior of corner reinforced concrete(RC)joints is the focus of this study.First,a detailed finite element(FE)model using the FE software Abaqus,is developed and validated using the test results from the literature.The validated modeling procedure is used to conduct a parametric study to investigate the influence of different parameters such as concrete strength,dimensions of main and transverse beams framing into the joint,presence or absence of a slab,axial load ratio and loading direction on the seismic behavior of joints.By subjecting the models to different combinations of loads on the beams along perpendicular directions,the interaction of the joint shear strength in two orthogonal directions is studied.The comparison of the interaction curves of the joints obtained from the numerical study with a quadratic(circular)interaction curve indicates that in a majority of cases,the quadratic interaction model can represent the strength interaction diagrams of RC beam to column connections with governing joint shear failure reasonably well.
基金National Key R&D Program of China(2022YFB2602900)R&D Fund Project of China Academy of Railway Sciences Corporation Limited(2021YJ084)+2 种基金Project of Science and Technology R&D Program of China Railway(2016G002-K)R&D Fund Project of China Railway Major Bridge Reconnaissance&Design Institute Co.,Ltd.(2021)R&D Fund Project of China Railway Shanghai Group(2021141).
文摘Purpose–The bridge expansion joint(BEJ)is a key device for accommodating spatial displacement at the beam end,and for providing vertical support for running trains passing over the gap between the main bridge and the approach bridge.For long-span railway bridges,it must also be coordinated with rail expansion joint(REJ),which is necessary to accommodate the expansion and contraction of,and reducing longitudinal stress in,the rails.The main aim of this study is to present analysis of recent developments in the research and application of BEJs in high-speed railway(HSR)long-span bridges in China,and to propose a performance-based integral design method for BEJs used with REJs,from both theoretical and engineering perspectives.Design/methodology/approach–The study first presents a summary on the application and maintenance of BEJs in HSR long-span bridges in China representing an overview of their state of development.Results of a survey of typical BEJ faults were analyzed,and field testing was conducted on a railway cable-stayed bridge in order to obtain information on the major mechanical characteristics of its BEJ under train load.Based on the above,a performance-based integral design method for BEJs with maximum expansion range 1600 mm(±800 mm),was proposed,covering all stages from overall conceptual design to consideration of detailed structural design issues.The performance of the novel BEJ design thus derived was then verified via theoretical analysis under different scenarios,full-scale model testing,and field testing and commissioning.Findings–Two major types of BEJs,deck-type and through-type,are used in HSR long-span bridges in China.Typical BEJ faults were found to mainly include skewness of steel sleepers at the bridge gap,abnormally large longitudinal frictional resistance,and flexural deformation of the scissor mechanisms.These faults influence BEJ functioning,and thus adversely affect track quality and train running performance at the beam end.Due to their simple and integral structure,deck-type BEJs with expansion range 1200 mm(±600 mm)or less have been favored as a solution offering improved operational conditions,and have emerged as a standard design.However,when the expansion range exceeds the above-mentioned value,special design work becomes necessary.Therefore,based on engineering practice,a performance-based integral design method for BEJs used with REJs was proposed,taking into account four major categories of performance requirements,i.e.,mechanical characteristics,train running quality,durability and insulation performance.Overall BEJ design must mainly consider component strength and the overall stiffness of BEJ;the latter factor in particular has a decisive influence on train running performance at the beam end.Detailed BEJ structural design must stress minimization of the frictional resistance of its sliding surface.The static and dynamic performance of the newlydesigned BEJ with expansion range 1600 mm have been confirmed to be satisfactory,via numerical simulation,full-scale model testing,and field testing and commissioning.Originality/value–This research provides a broad overview of the status of BEJs with large expansion range in HSR long-span bridges in China,along with novel insights into their design.
文摘The clinical treatment of severe trauma withsternoclavicular joint injury is challenging,primarilydue to the irregular shape of the bones surrounding thesternoclavicular joint,as well as the posterior clavicle beingclose to the aorta and mediastinal organs.^([1])These patientsnot only suffer direct injuries to the sternoclavicularjoint,but also frequently experience severe injuries toother body parts.The systemic physiological disordersand multi-organ dysfunction caused by severe traumaincrease the surgery di?culty and mortality risk.^([2])
基金financial support from the National Natural Science Foundation of China(Grant Nos.52074269,52474157 and 51979272).
文摘Rock joints always have a smaller strength,and it plays an important influence on the overall strength of rock mass.The mechanical behavior of rock joints is mainly governed by the surface topography,normal stress,and failure degree.In this study,a series of direct shear tests for four different rough rock joints under five normal stresses was carried out.The shear and normal stiffnesses were first determined,and the shear shrinkage effect was represented by a shear-normal coupling coefficient.Assuming that the strength of the joint is composed of frictional and cohesive parts,the evolutions of cohesion,friction angle with joint roughness coefficient(JRC),and plastic shear displacement are obtained.The dilatancy behavior is described by the dilation angle,which is considered a function of JRC,plastic shear displacement,and normal stress.A cohesive-frictional elastoplastic constitutive model is hence proposed.The theoretical curves under constant normal stress conditions of the proposed model are in good agreement with the experimental results.The shear behaviors under constant normal stiffness and constant normal displacement conditions can be predicted using the new constitutive model.
基金supported by the National Natural Science Foundation of China(No.42207175)。
文摘The joint roughness coefficient(JRC) is one of the key parameters for evaluating the shear strength of rock joints.Because of the scale effect in the JRC,reliable JRC values are of great importance for most rock engineering projects.During the collection process of JRC samples,the redundancy or insufficiency of representative rock joint surface topography(RJST) information in serial length JRC samples is the essential reason that affects the reliability of the scale effect results.Therefore,this paper proposes an adaptive sampling method,in which we use the entropy consistency measure Q(a) to evaluate the consistency of the joint morphology information contained in adjacent JRC samples.Then the sampling interval is automatically adjusted according to the threshold Q(at) of the entropy consistency measure to ensure that the degree of change of RJST information between JRC samples is the same,and ultimately makes the representative RJST information in the collected JRC samples more balanced.The application results of actual cases show that the proposed method can obtain the scale effect in the JRC efficiently and reliably.
文摘The configuration of underground powerhouses is crucial in pumped-storage hydropower projects,which play a vital role in maintaining grid stability,facilitating the integration of renewable energy sources,and managing flood risks.However,geotechnical challenges,such as complex joint orientations,anisotropy in in-situ stress,and rock damage caused by excavation,require thorough stability assessments.This research employs the ubiquitous anisotropic joint model within FLAC3D to investigate the effects of joint dip angle,joint dip direction,and the alignment of in-situ stress on the stability of surrounding rock formations.The key parameters analyzed include joint cohesion,friction angle,and the magnitude of in-situ stress.The numerical results indicate that deformation is minimized when the axis of the powerhouse is aligned with the major principal stress.Furthermore,joint dip angles between 65°and 70°lead to a 50%reduction in both displacement and plastic zone volume.Additionally,angles less than 40°between the joint dip direction and the powerhouse axis enhance stability.These findings provide practical recommendations for optimizing the orientation of powerhouses in geomechanical contexts similar to those characterized by foliated sericite phyllite with moderate joint persistence.
基金Project(GZB202405561)supported by the Postdoctoral Fellowship Program of China Postdoctoral Science FoundationProject(42377154)supported by the National Natural Science Foundation of China。
文摘The shear performance of bolts plays a crucial role in controlling rock mass stability,and the roughness of the joint surface is one of the main factors affecting the mechanical properties of anchored joints.The 2nd generation of negative Poisson ratio(2G-NPR)bolt is a new independently developed material characterized by high strength and toughness.However,the influence of joint surface roughness on its anchorage shear performance remains unexplored.This study involves preparing regular saw-tooth jointed rock masses and conducting laboratory shear comparison tests on unbolted samples,2G-NPR bolts,and Q235 steel anchors.A three-dimensional finite element method,developed by the author,was employed for numerical simulations to analyze the influence of saw-tooth angles on the shear resistance of anchored bolts.The findings show that the anchorage of bolts enhances the shear strength and deformation of saw-tooth rock joints.The 2G-NPR bolts demonstrate superior performance in shear strength and deformation enhancement compared to Q235 steel anchors,including improved toughening and crack-arresting effects.Furthermore,the improvement of the shear strength and displacement of the bolt decreases with the increase of the joint saw-tooth angle.These findings provide a valuable test basis for the engineering application of 2G-NPR bolts in rock mass stabilization.
基金supported by the National Natural Science Foundation of China Nos.82370983,81671015(X.W.),82230030(Y.L.),82101043(S.C.)and 82370922(Y.F.)Beijing International Science and Technology Cooperation Project No.Z221100002722003(Y.L.)+4 种基金Beijing Natural Science Foundation Nos.L234017,JL23002(Y.L.),No.7242282(S.C.)and 7232217(Y.G.)Clinical Medicine Plus X-Young Scholars Project of Peking University No.PKU2024LCXQ039(Y.L.)National Program for Multidisciplinary Cooperative Treatment on Major Diseases No.PKUSSNMP-202013(X.W.)Hygiene and Health Development Scientific Research Fostering Plan of Haidian District Beijing No.HP2023-12-509001(J.Z.)Young Clinical Research Fund of the Chinese Stomatological Association No.CSA-02022-03(J.Z.).
文摘Temporomandibular joint(TMJ)disc displacement is one of the most significant subtypes of temporomandibular joint disorders,but its etiology and mechanism are poorly understood.In this study,we elucidated the mechanisms by which destruction of inflamed collagen fibrils induces alterations in the mechanical properties and positioning of the TMJ disc.By constructing a rat model of TMJ arthritis,we observed anteriorly dislocated TMJ discs with aggravated deformity in vivo from five weeks to six months after a local injection of Freund’s complete adjuvant.By mimicking inflammatory conditions with interleukin-1 beta in vitro,we observed enhanced expression of collagen-synthesis markers in primary TMJ disc cells cultured in a conventional two-dimensional environment.In contrast,three-dimensional(3D)-cultivated disc cell sheets demonstrated the disordered assembly of inflamed collagen fibrils,inappropriate arrangement,and decreased Young’s modulus.Mechanistically,inflammation-related activation of the nuclear factor kappa-B(NF-κB)pathway occurs during the progression of TMJ arthritis.NF-κB inhibition reduced the collagen fibril destruction in the inflamed disc cell sheets in vitro,and early NF-κB blockade alleviated collagen degeneration and dislocation of the TMJ discs in vivo.Therefore,the NF-κB pathway participates in the collagen remodeling in inflamed TMJ discs,offering a potential therapeutic target for disc displacement.
文摘Purpose–This study aims to investigate the fatigue behavior and failure modes of bolted lap joints using Modified Tensile Specimens(MTS)under various cyclic load conditions.Emphasis is placed on identifying the relationship between load amplitude,fatigue life,and damage progression in low-carbon steel assemblies.Design/methodology/approach–An experimental approach was adopted using MTS specimens fabricated from St 1203 cold-rolled steel,joined with Grade 8.8 M4 bolts.Cyclic fatigue tests were conducted under zerobased loading at seven distinct force levels.Fracture surfaces were visually analyzed to identify dominant failure mechanisms.Findings–The results revealed a strong inverse correlation between applied cyclic load and fatigue life.Three distinct failure modes were identified:bolt shear at high loads(5.4 kN),interface cracking and slippage at moderate loads(4.9–5.1 kN),and plate tearing or stable fatigue behavior at lower loads(54.1 kN).The results highlight a progressive transition in failure mechanisms,from bolt shear at high loads to plate tearing and interface cracking at lower loads,providing essential insights for fatigue-resistant bolted joint design.Originality/value–This study offers original insights into the fatigue behavior of bolted lap joints using MTS,a relatively underexplored configuration in fatigue assessment.By experimentally evaluating failure modes under varied cyclic load levels,the authors uncover critical transitions in damage mechanisms—from bolt shear to interface cracking and plate tearing—depending on the applied load.Unlike many existing studies focused on numerical modeling or bonded joints alone,this work provides empirical data rooted in real-world fastening conditions using cold-rolled low-carbon steel.
基金funded by the National Natural Science Foundation of China(Grant Nos.42472345,52325905,42407202).
文摘The joint roughness coefficient(JRC)is a key parameter in the assessment of mechanical properties and the stability of rock masses.This paper presents a novel approach to JRC evaluation using a genetic algorithm-optimized backpropagation(GA-BP)neural network.Conventional JRC evaluations have typically depended on two-dimensional(2D)and three-dimensional(3D)parameter calculation methods,which fail to fully capture the nonlinear relationship between the complex surface morphology of joints and their roughness.Our analysis from shear tests on eight different joint types revealed that the strength and failure characteristics of the joints not only exhibit directional dependence but also positively correlate with surface dip angles,heights,and back slope morphological features.Subsequently,five simple statistical parameters,i.e.average dip angle,median dip angle,average height,height coefficient of variation,and back slope feature value(K),were utilized to quantify these characteristics.For the prediction of JRC,we compiled and analyzed 105 datasets,each containing these five statistical parameters and their corresponding JRC values.A GA-BP neural network model was then constructed using this dataset,with the five morphological characteristic statistics serving as inputs and the JRC values as outputs.A comparative analysis was performed between the GA-BP neural network model,the statistical parameter method,and the fractal parameter method.This analysis confirmed that our proposed method offers higher accuracy in evaluating the roughness coefficient and shear strength of joints.
基金funded by the National Natural Science Foundation Projects(Grant Nos.41772287 and 42277132)the Key R&D Project of Zhejiang Province(Grant No.2021C03159).
文摘The scale effect on shear strength of rock joints is well-documented.However,whether scale effects are negative,positive,or even exist or not is still controversial.Joint roughness significantly influences the shear strength of rock joints.Compared to the shear tests,using the joint roughness coefficient(JRC)and its roughness parameters offers a more convenient method for describing the scale effect on shear strength.However,it is crucial to understand that the scale effect mechanisms of JRC are distinct from those of shear strength.Therefore,this paper aims to clarify these distinct mechanisms.By digitally extracting roughness parameters from granite samples,it is found that the scale effect of roughness parameters mainly comes from the sampling methods and the geometric characteristics of parameters.Furthermore,a full data sampling method considering heterogeneity is proposed to obtain more representative roughness parameters.To reveal the scale effect mechanisms of shear strength,Gaussian filtering is firstly used to separate the waviness and unevenness components of roughness,facilitating a deeper understanding of the geometric characteristics of roughness.It is suggested that the wavelength of the waviness component can reflect the scale effect on shear strength.Secondly,numerical simulations of ideal artificial joint models are conducted to validate that the wavelength of the waviness component serves as the dividing point between positive and negative scale effects.The mechanical mechanisms of positive and negative scale effects are also interpreted.Finally,these mechanisms successfully elucidate the occurrence patterns of the scale effect on natural joint profiles.
基金supported by the Na⁃tional Natural Science Foundation of China(No.U22A20204)the Innovation Foundation from National Clinical Research Center for Orthopedics,Sports Medicine&Rehabilitation Foundation(No.23-NCRC-CXJJ-ZD3-8)。
文摘Human-robot safety is an important topic in wearable robotics,especially in supernumerary robotic limbs(SRLs).The proposal of flexible joint improves human-robot safety strategy,which allows physical contact between human and robots,rather than strictly limiting the human-robot motion.However,most researchers focus on the variable stiffness features of flexible joints,but few evaluate the performance of the flexible joint in the human-robot collision.Therefore,the performance of two typical flexible joints,including the series elastic joint(SEJ)and the passive variable stiffness joint(PVSJ),are compared through dynamic collision experiments.The results demonstrate that the SEJ absorbs 40.7%-58.7%of the collision force and 34.2%-45.2%of the collision torque in the driven-torque below 4 N·m and driven-speed of 3-7(°)/s,which is more stable than PVSJ.In addition,the stiffness error of SEJ is measured at 5.1%,significantly lower than the 23.04%measured in the PVSJ.The huge stiffness error of PVSJ leads to its unreliability in buffering collision.Furthermore,we analyze results and confirm that SEJ has a more stable human-robot safety performance in buffering dynamic collision.Consequently,the SEJ is suitable in SRLs for human-robot safety in our scenario.
基金supported in part by the National Key R&D Program of China under Grant 2022YFB3103500in part by the National Natural Science Foundation of China under Grant 62302195.
文摘Semantic secure communication is an emerging field that combines the principles of source-channel coding with the need for secure data transmission.It is of great significance in modern communications to protect the confidentiality and privacy of sensitive information and prevent information leaks and malicious attacks.This paper presents a novel approach to semantic secure communication through the utilization of joint source-channel coding,which is based on the design of an automated joint source-channel coding algorithm and an encryption and decryption algorithm based on semantic security.The traditional and state-of-the-art joint source-channel coding algorithms are selected as two baselines for different comparison purposes.Experimental results demonstrate that our proposed algorithm outperforms the first baseline algorithm,the traditional source-channel coding,by 61.21%in efficiency under identical channel conditions(SNR=15 dB).In security,our proposed method can resist 2 more types of attacks compared to the two baselines,exhibiting nearly no increases in time consumption and error rate compared to the state-of-the-art joint source-channel coding algorithm while the secure semantic communication is supported.
基金supported by Fundamental Research Funds for the Central Universities,CHD300102264715National Key Research and Development Program of China under Grant 2021YFA0716902Natural Science Basic Research Program of Shaanxi 2024JCYBMS-199。
文摘Young's modulus and Poisson's ratio are crucial parameters for reservoir characterization and rock brittleness evaluation.Conventional methods often rely on indirect computation or approximations of the Zoeppritz equations to estimate Young's modulus,which can introduce cumulative errors and reduce the accuracy of inversion results.To address these issues,this paper introduces the analytical solution of the Zoeppritz equation into the inversion process.The equation is re-derived and expressed in terms of Young's modulus,Poisson's ratio,and density.Within the Bayesian framework,we construct an objective function for the joint inversion of PP and PS waves.Traditional gradient-based algorithms often suffer from low precision and the computational complexity.In this study,we address limitations of conventional approaches related to low precision and complicated code by using Circle chaotic mapping,Levy flights,and Gaussian mutation to optimize the quantum particle swarm optimization(QPSO),named improved quantum particle swarm optimization(IQPSO).The IQPSO demonstrates superior global optimization capabilities.We test the proposed inversion method with both synthetic and field data.The test results demonstrate the proposed method's feasibility and effectiveness,indicating an improvement in inversion accuracy over traditional methods.
基金supported by the National Key R&D Program of China(No.2023YFC3081200)the National Natural Science Foundation of China(No.42077264)。
文摘To map the rock joints in the underground rock mass,a method was proposed to semiautomatically detect the rock joints from borehole imaging logs using a deep learning algorithm.First,450 images containing rock joints were selected from borehole ZKZ01 in the Rumei hydropower station.These images were labeled to establish ground truth which was subdivided into training,validation,and testing data.Second,the YOLO v2 model with optimal parameter settings was constructed.Third,the training and validation data were used for model training,while the test data was used to generate the precision-recall curve for prediction evaluation.Fourth,the trained model was applied to a new borehole ZKZ02 to verify the feasibility of the model.There were 12 rock joints detected from the selected images in borehole ZKZ02 and four geometric parameters for each rock joint were determined by sinusoidal curve fitting.The average precision of the trained model reached 0.87.
基金Project(52278421)supported by the National Natural Science Foundation of ChinaProject(2024ZZTS0754)supported by the Fundamental Research Funds for the Central Universities of Central South University,China+2 种基金Project(2023CXQD067)supported by the Central South University Innovation-Driven Research Programme,ChinaProject(2022QNRC001)supported by Young Elite Scientists Sponsorship Program by CASTProject(2023TJ-N24)supported by the Youth Talent Program by China Railway Society and the Hunan Provincial Science and Technology Promotion Talent Project。
文摘Waterproof performance of gaskets between segments is the focus of shield tunnels.This paper proposed an analytical method for determining seepage characteristics at tunnel-gasketed joints based on the hydraulic fracturing theories.First,the mathematical model was established,and the seepage governing equation and boundary conditions were obtained.Second,three dimensionless parameters were introduced for simplifying the expressions,and the seepage governing equations were normalized.Third,analytical expressions were derived for the interface opening and liquid pressure.Moreover,the influencing factors of seepage process at the gasketed interface were analyzed.Parametric analyses revealed that,in the normalized criterion of liquid viscosity,the liquid tip coordinate was influenced by the degree of negative pressure in the liquid lag region,which was related to the initial contact stress.The coordinate of the liquid tip affected the liquid pressure distribution and the interface opening,which were analyzed under different liquid tip coordinate conditions.Finally,under two limit states,comparative analysis showed that the results of the variation trend of the proposed method agree well with those of previous research.Overall,the proposed analytical method provides a novel solution for the design of the waterproof in shield tunnels.
基金financially supported by the National Natural Science Foundation of China(Grant No.42172292)Taishan Scholars Project Special Funding,and Shandong Energy Group(Grant No.SNKJ 2022A01-R26).
文摘A conceptual model of intermittent joints is introduced to the cyclic shear test in the laboratory to explore the effects of loading parameters on its shear behavior under cyclic shear loading.The results show that the loading parameters(initial normal stress,normal stiffness,and shear velocity)determine propagation paths of the wing and secondary cracks in rock bridges during the initial shear cycle,creating different morphologies of macroscopic step-path rupture surfaces and asperities on them.The differences in stress state and rupture surface induce different cyclic shear responses.It shows that high initial normal stress accelerates asperity degradation,raises shear resistance,and promotes compression of intermittent joints.In addition,high normal stiffness provides higher normal stress and shear resistance during the initial cycles and inhibits the dilation and compression of intermittent joints.High shear velocity results in a higher shear resistance,greater dilation,and greater compression.Finally,shear strength is most sensitive to initial normal stress,followed by shear velocity and normal stiffness.Moreover,average dilation angle is most sensitive to initial normal stress,followed by normal stiffness and shear velocity.During the shear cycles,frictional coefficient is affected by asperity degradation,backfilling of rock debris,and frictional area,exhibiting a non-monotonic behavior.
基金funding from the National Natural Science Foundation of China (Grant No.42277175)the pilot project of cooperation between the Ministry of Natural Resources and Hunan Province“Research and demonstration of key technologies for comprehensive remote sensing identification of geological hazards in typical regions of Hunan Province” (Grant No.2023ZRBSHZ056)the National Key Research and Development Program of China-2023 Key Special Project (Grant No.2023YFC2907400).
文摘Joint roughness coefficient(JRC)is the most commonly used parameter for quantifying surface roughness of rock discontinuities in practice.The system composed of multiple roughness statistical parameters to measure JRC is a nonlinear system with a lot of overlapping information.In this paper,a dataset of eight roughness statistical parameters covering 112 digital joints is established.Then,the principal component analysis method is introduced to extract the significant information,which solves the information overlap problem of roughness characterization.Based on the two principal components of extracted features,the white shark optimizer algorithm was introduced to optimize the extreme gradient boosting model,and a new machine learning(ML)prediction model was established.The prediction accuracy of the new model and the other 17 models was measured using statistical metrics.The results show that the prediction result of the new model is more consistent with the real JRC value,with higher recognition accuracy and generalization ability.
