Quantitative analysis of clinical function parameters from MRI images is crucial for diagnosing and assessing cardiovascular disease.However,the manual calculation of these parameters is challenging due to the high va...Quantitative analysis of clinical function parameters from MRI images is crucial for diagnosing and assessing cardiovascular disease.However,the manual calculation of these parameters is challenging due to the high variability among patients and the time-consuming nature of the process.In this study,the authors introduce a framework named MultiJSQ,comprising the feature presentation network(FRN)and the indicator prediction network(IEN),which is designed for simultaneous joint segmentation and quantification.The FRN is tailored for representing global image features,facilitating the direct acquisition of left ventricle(LV)contour images through pixel classification.Additionally,the IEN incorporates specifically designed modules to extract relevant clinical indices.The authors’method considers the interdependence of different tasks,demonstrating the validity of these relationships and yielding favourable results.Through extensive experiments on cardiac MR images from 145 patients,MultiJSQ achieves impressive outcomes,with low mean absolute errors of 124 mm^(2),1.72 mm,and 1.21 mm for areas,dimensions,and regional wall thicknesses,respectively,along with a Dice metric score of 0.908.The experimental findings underscore the excellent performance of our framework in LV segmentation and quantification,highlighting its promising clinical application prospects.展开更多
In this article,the mechanical properties of tunnel joints with curved bolts are studied and analyzed using the research methods of full-scale testing and finite element numerical simulation.First,the experiment resul...In this article,the mechanical properties of tunnel joints with curved bolts are studied and analyzed using the research methods of full-scale testing and finite element numerical simulation.First,the experiment results were analyzed to find out the development law of stress and strain of concrete in each part of the tunnel fragment when bearing.The damage process of the joint of the tunnel fragment was described in stages,and the characteristic load value that can reflect the initial bearing capacity in each stage was proposed.Afterward,using the ABAQUS three-dimensional(3D)finite element numerical modeling software,a numerical model corresponding to the experiment was established.The mid-span deflection was used to observe the change in loading and the destruction of each stage,comparing it to the proposed form to verify the reasonableness of the numerical model.Finally,the numerical models were used to analyze the change in material parameters and external loads from two aspects.It is concluded that the damage process of tunnel joints under curved bolt connection can be divided into concrete elasticity stage,inner arc cracking stage,overall joint damage stage,and ultimate joint damage stage,and the initial load of the adjacent stages is defined as the characteristic load value.After concrete cracking occurs,the bolts start to become the main load-bearing components,and the bolt stress grows rapidly in stage II.The strain development of the concrete on the outer arc is greater than the strain value of the concrete on the side due to mutual contact and extrusion.The parameters were changed for material properties,and it was found that increasing the concrete strength and bolt strength could improve the shield fragment joint bearing performance.The optimal effect of improving the mechanical properties of the shield fragment joint would be obtained when the concrete strength grade is C60,and the bolt strength grade is 8.8.Increasing the size of the axial force and bolt preload has the most obvious effect on the load-carrying capacity in the initial elastic phase.This can reduce the joint angle and thus improve joint stiffness.Meanwhile,increasing the axial force has a greater effect on the performance of the tunnel joint than the bolt preload.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
We develop assembled reinforcement structures(ARSs)composed of connection parts,connecting rods,and straight bolts to strengthen segmental joints in the lining of shield tunnels.Through full-scale bending experiments ...We develop assembled reinforcement structures(ARSs)composed of connection parts,connecting rods,and straight bolts to strengthen segmental joints in the lining of shield tunnels.Through full-scale bending experiments and numerical simulations,we investigate the deformation and failure characteristics of segmental joints strengthened by ARSs,and propose a novel optimization method for ARSs.The experimental results show that the ARSs can effectively limit the opening of a segmental joint,but also that separation can occur during loading if the connection between the ARSs and segments is not designed properly.Importantly,this connection can be improved by embedding anchor parts in the concrete.In numerical modeling,we investigate the failure modes of segmental joints strengthened by ARSs for both positive bending and negative bending loading cases.In the case of positive bending loading,first the concrete around the anchor parts cracks,and subsequently the concrete on the external side of the joint is crushed.The joint failure is caused by the crushing of concrete on the external side of the joint.While the un-strengthened segmental joint fails with an opening of 5.884 mm,the strengthened segmental joint only opens by 0.288 mm under the same loading,corresponding to a reduction of 95.1%.In the case of negative bending loading,the concrete around the anchor parts first cracks,and then the amount of joint opening exceeds a limiting value for waterproofing(6 mm),i.e.,the joint’s failure is caused by water leakage.While the opening of the un-strengthened segmental joint is 9.033 mm and experiences waterproofing failure,the opening of the strengthened segmental joint is only 2.793 mm under the same loading,corresponding to a reduction of 69.1%.When constructing a new shield tunnel,anchor parts could be embedded in the concrete segments in tandem with ARSs for improved resistance to joint opening.For existing shield tunnel linings,anchor parts cannot be embedded in the concrete segments;therefore,the connections between the ARSs and concrete need to be optimized to strengthen the segmental joint.展开更多
Sn/Ni-Sn/Sn sandwich joining piece was developed and applied to fabricate segmented half-Heusler/skutterudite thermoelectric joints,and high-temperature service behavior of the joints was studied.The microstructure an...Sn/Ni-Sn/Sn sandwich joining piece was developed and applied to fabricate segmented half-Heusler/skutterudite thermoelectric joints,and high-temperature service behavior of the joints was studied.The microstructure and contact resistance of the joint before and after aging were investigated.The joints are well bonded and no cracks appear at the interfaces of the joint before and after aging,which can be attributed to the formation of high-melting point intermetallic compounds.The electrical resistance crosses the joining layer smoothly and the contact resistance is low.These results show that the sandwich joining piece is effective and flexible,and promising for the preparation of segmented thermoelectric devices.展开更多
Passive dynamic walking has been developed as a possible explanation for the efficiency of the human gait. This paper presents a passive dynamic walking model with segmented feet, which makes the bipedal walking gait ...Passive dynamic walking has been developed as a possible explanation for the efficiency of the human gait. This paper presents a passive dynamic walking model with segmented feet, which makes the bipedal walking gait more close to natural human-like gait. The proposed model extends the simplest walking model with the addition of fiat feet and torsional spring based compliance on ankle joints and toe joints, to achieve stable walking on a slope driven by gravity. The push-off phase includes foot rotations around the toe joint and around the toe tip, which shows a great resemblance to human normal walking. This paper investigates the effects of the segmented foot structure on bipedal walking in simulations. The model achieves satisfactory walking results on even or uneven slopes.展开更多
基金Hefei Municipal Natural Science Foundation,Grant/Award Number:2022009Suqian Guiding Program Project,Grant/Award Number:Z202309Suqian Traditional Chinese Medicine Science and Technology Plan,Grant/Award Number:MS202301。
文摘Quantitative analysis of clinical function parameters from MRI images is crucial for diagnosing and assessing cardiovascular disease.However,the manual calculation of these parameters is challenging due to the high variability among patients and the time-consuming nature of the process.In this study,the authors introduce a framework named MultiJSQ,comprising the feature presentation network(FRN)and the indicator prediction network(IEN),which is designed for simultaneous joint segmentation and quantification.The FRN is tailored for representing global image features,facilitating the direct acquisition of left ventricle(LV)contour images through pixel classification.Additionally,the IEN incorporates specifically designed modules to extract relevant clinical indices.The authors’method considers the interdependence of different tasks,demonstrating the validity of these relationships and yielding favourable results.Through extensive experiments on cardiac MR images from 145 patients,MultiJSQ achieves impressive outcomes,with low mean absolute errors of 124 mm^(2),1.72 mm,and 1.21 mm for areas,dimensions,and regional wall thicknesses,respectively,along with a Dice metric score of 0.908.The experimental findings underscore the excellent performance of our framework in LV segmentation and quantification,highlighting its promising clinical application prospects.
基金financial support provided by the National Natural Science Foundation of China under(Grant Nos.51978019 and 52278382)the Natural Science Foundation of Beijing Municipality(No.8222004).
文摘In this article,the mechanical properties of tunnel joints with curved bolts are studied and analyzed using the research methods of full-scale testing and finite element numerical simulation.First,the experiment results were analyzed to find out the development law of stress and strain of concrete in each part of the tunnel fragment when bearing.The damage process of the joint of the tunnel fragment was described in stages,and the characteristic load value that can reflect the initial bearing capacity in each stage was proposed.Afterward,using the ABAQUS three-dimensional(3D)finite element numerical modeling software,a numerical model corresponding to the experiment was established.The mid-span deflection was used to observe the change in loading and the destruction of each stage,comparing it to the proposed form to verify the reasonableness of the numerical model.Finally,the numerical models were used to analyze the change in material parameters and external loads from two aspects.It is concluded that the damage process of tunnel joints under curved bolt connection can be divided into concrete elasticity stage,inner arc cracking stage,overall joint damage stage,and ultimate joint damage stage,and the initial load of the adjacent stages is defined as the characteristic load value.After concrete cracking occurs,the bolts start to become the main load-bearing components,and the bolt stress grows rapidly in stage II.The strain development of the concrete on the outer arc is greater than the strain value of the concrete on the side due to mutual contact and extrusion.The parameters were changed for material properties,and it was found that increasing the concrete strength and bolt strength could improve the shield fragment joint bearing performance.The optimal effect of improving the mechanical properties of the shield fragment joint would be obtained when the concrete strength grade is C60,and the bolt strength grade is 8.8.Increasing the size of the axial force and bolt preload has the most obvious effect on the load-carrying capacity in the initial elastic phase.This can reduce the joint angle and thus improve joint stiffness.Meanwhile,increasing the axial force has a greater effect on the performance of the tunnel joint than the bolt preload.
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supported by the National Natural Science Foundation of China(No.52008308)the China Postdoctoral Science Foundation(Nos.BX20200247 and 2021M692447)the Research Project from Jinan Rail Transit Group Co.,Ltd.and China Railway No.5 Engineering Group Co.,Ltd.(No.R2-ZF-2019-039).
文摘We develop assembled reinforcement structures(ARSs)composed of connection parts,connecting rods,and straight bolts to strengthen segmental joints in the lining of shield tunnels.Through full-scale bending experiments and numerical simulations,we investigate the deformation and failure characteristics of segmental joints strengthened by ARSs,and propose a novel optimization method for ARSs.The experimental results show that the ARSs can effectively limit the opening of a segmental joint,but also that separation can occur during loading if the connection between the ARSs and segments is not designed properly.Importantly,this connection can be improved by embedding anchor parts in the concrete.In numerical modeling,we investigate the failure modes of segmental joints strengthened by ARSs for both positive bending and negative bending loading cases.In the case of positive bending loading,first the concrete around the anchor parts cracks,and subsequently the concrete on the external side of the joint is crushed.The joint failure is caused by the crushing of concrete on the external side of the joint.While the un-strengthened segmental joint fails with an opening of 5.884 mm,the strengthened segmental joint only opens by 0.288 mm under the same loading,corresponding to a reduction of 95.1%.In the case of negative bending loading,the concrete around the anchor parts first cracks,and then the amount of joint opening exceeds a limiting value for waterproofing(6 mm),i.e.,the joint’s failure is caused by water leakage.While the opening of the un-strengthened segmental joint is 9.033 mm and experiences waterproofing failure,the opening of the strengthened segmental joint is only 2.793 mm under the same loading,corresponding to a reduction of 69.1%.When constructing a new shield tunnel,anchor parts could be embedded in the concrete segments in tandem with ARSs for improved resistance to joint opening.For existing shield tunnel linings,anchor parts cannot be embedded in the concrete segments;therefore,the connections between the ARSs and concrete need to be optimized to strengthen the segmental joint.
基金the National Natural Science Foundation of China(Nos.U1738114,51372261 and 51879089)。
文摘Sn/Ni-Sn/Sn sandwich joining piece was developed and applied to fabricate segmented half-Heusler/skutterudite thermoelectric joints,and high-temperature service behavior of the joints was studied.The microstructure and contact resistance of the joint before and after aging were investigated.The joints are well bonded and no cracks appear at the interfaces of the joint before and after aging,which can be attributed to the formation of high-melting point intermetallic compounds.The electrical resistance crosses the joining layer smoothly and the contact resistance is low.These results show that the sandwich joining piece is effective and flexible,and promising for the preparation of segmented thermoelectric devices.
基金supported by the National Natural Science Foundation of China (61005082, 61020106005)Doctoral Fund of Ministry of Education of China (20100001120005)+1 种基金PKU-Biomedical Engineering Join Seed Grant 2012the 985 Project of PekingUniversity (3J0865600)
文摘Passive dynamic walking has been developed as a possible explanation for the efficiency of the human gait. This paper presents a passive dynamic walking model with segmented feet, which makes the bipedal walking gait more close to natural human-like gait. The proposed model extends the simplest walking model with the addition of fiat feet and torsional spring based compliance on ankle joints and toe joints, to achieve stable walking on a slope driven by gravity. The push-off phase includes foot rotations around the toe joint and around the toe tip, which shows a great resemblance to human normal walking. This paper investigates the effects of the segmented foot structure on bipedal walking in simulations. The model achieves satisfactory walking results on even or uneven slopes.
