This research explores the potential for the evaluation and prediction of earth pressure balance shield performance based on a gray system model.The research focuses on a shield tunnel excavated for Metro Line 2 in Da...This research explores the potential for the evaluation and prediction of earth pressure balance shield performance based on a gray system model.The research focuses on a shield tunnel excavated for Metro Line 2 in Dalian,China.Due to the large error between the initial geological exploration data and real strata,the project construction is extremely difficult.In view of the current situation regarding the project,a quantitative method for evaluating the tunneling efficiency was proposed using cutterhead rotation(R),advance speed(S),total thrust(F)and torque(T).A total of 80 datasets with three input parameters and one output variable(F or T)were collected from this project,and a prediction framework based gray system model was established.Based on the prediction model,five prediction schemes were set up.Through error analysis,the optimal prediction scheme was obtained from the five schemes.The parametric investigation performed indicates that the relationships between F and the three input variables in the gray system model harmonize with the theoretical explanation.The case shows that the shield tunneling performance and efficiency are improved by the tunneling parameter prediction model based on the gray system model.展开更多
This paper presents a simplified elastic continuum method for calculating the restraint effect of isolation piles on tunneling-induced vertical ground displacement,which can consider not only the relative sliding of t...This paper presents a simplified elastic continuum method for calculating the restraint effect of isolation piles on tunneling-induced vertical ground displacement,which can consider not only the relative sliding of the pile‒soil interface but also the pile rowesoil interaction.The proposed method is verified by comparisons with existing theoretical methods,including the boundary element method and the elastic foundation method.The results reveal the restraining mechanism of the isolation piles on vertical ground displacements due to tunneling,i.e.the positive and negative restraint effects exerted by the isolation piles jointly drive the ground vertical displacement along the depth direction from the original tunneling-induced nonlinear variation situation to a relatively uniform situation.The results also indicate that the stiffness of the pile‒soil interface,including the pile shaft‒surrounding soil interface and pile tip-supporting soil interface,describes the strength of the pile‒soil interaction.The pile rows can confine the vertical ground displacement caused by the tunnel excavation to the inner side of the isolation piles and effectively prevent the vertical ground displacement from expanding further toward the outer side of the isolation piles.展开更多
This study presents a framework for predicting geological characteristics based on integrating a stacking classification algorithm(SCA) with a grid search(GS) and K-fold cross validation(K-CV). The SCA includes two le...This study presents a framework for predicting geological characteristics based on integrating a stacking classification algorithm(SCA) with a grid search(GS) and K-fold cross validation(K-CV). The SCA includes two learner layers: a primary learner’s layer and meta-classifier layer. The accuracy of the SCA can be improved by using the GS and K-CV. The GS was developed to match the hyper-parameters and optimise complicated problems. The K-CV is commonly applied to changing the validation set in a training set. In general, a GS is usually combined with K-CV to produce a corresponding evaluation index and select the best hyper-parameters. The torque penetration index(TPI) and field penetration index(FPI) are proposed based on shield parameters to express the geological characteristics. The elbow method(EM) and silhouette coefficient(Si) are employed to determine the types of geological characteristics(K) in a Kmeans++ algorithm. A case study on mixed ground in Guangzhou is adopted to validate the applicability of the developed model. The results show that with the developed framework, the four selected parameters, i.e. thrust, advance rate, cutterhead rotation speed and cutterhead torque, can be used to effectively predict the corresponding geological characteristics.展开更多
It is generally recognized that Caucasians and Asians have different skin aging features.The aim of this study was to develop a facial wrinkle grading scale for Chinese women.Standard photographs were taken of 242 Chi...It is generally recognized that Caucasians and Asians have different skin aging features.The aim of this study was to develop a facial wrinkle grading scale for Chinese women.Standard photographs were taken of 242 Chinese women.Six sets of 0 to 9 wrinkle scales with reference photographs and descriptions were selected,including grading scales for resting and hyperkinetic crow's feet,frontalis lines,glabellar frown lines,and nasolabial folds.To identify the scale by objective quantitative measurement,skin surface measurements from the Visioscan~ VC98 were used.To test the reliability and validity of our wrinkle scale,a multi-rater consensus method was used.A double-blind,randomized,vehicle-controlled 12-week study was conducted to use this clinical photo-score to evaluate the efficacy and safety of Centella triterpenes cream~ in treating crow's feet.A newly developed 10-point photographic and descriptive scale emerged from this study.The final atlas of these photographs contained a total of 6 sets with 10 pictures each.From 0 to 9,surface evaluation of smoothness(SEsm) parametric measurements decreased progressively,indicating that the scale increased inversely.Weighted kappa coefficients for intra-assessor were between 0.75-0.87.The overall Kendall's coefficient is 0.86 on the first rating and 0.87 on the second rating.Thirtysix volunteers were recruited and 35 subjects completed a 12-week trial.Clinical photo-score by investigator showed a significant difference(P < 0.05) between the treatment side and control side after 4 weeks.Use of these scales in clinical settings to evaluate facial wrinkles in Asians individuals is recommended.展开更多
With the rapid development of rail transit,effectively developing urban underground space(UUS)in the metro zone has become an important approach to expanding urban space.However,UUS is currently facing problems,such a...With the rapid development of rail transit,effectively developing urban underground space(UUS)in the metro zone has become an important approach to expanding urban space.However,UUS is currently facing problems,such as an uneven distribution or even loss of vitality,which restricts the utilization efficiency of the space.Thus,we established a UUS environmental assessment system based on the‘‘comfort-aesthetic-function-traffic-structure”using space syntax,instrumental measurement,and questionnaire surveys.By constructing a partial-least-square structural equation model,the internal relationships between the UUS environment and corresponding space vitality and space perception under different study areas,namely the underground transportation-oriented space(transportation space for short)and the underground commercial-oriented space(commercial space for short),were studied in detail throughout the working day.Results indicate the following:(1)the UUS in the metro zone environment influences spatial vitality.The vitality distribution of transportation space is significantly affected by the spatial traffic and structure.The vitality distribution of commercial space is significantly affected by the spatial function and traffic.(2)The environment of UUSs in the metro zone influences users’s perception.The perception of transportation space is significantly affected by aesthetics and comfort.The perception of commercial space is significantly affected by aesthetic,comfort,and spatial functions.(3)The user’s perception affects vitality,and the effect is more significant in commercial space.This study provides an in-depth understanding of the relationship between the complex environment and its spatial vitality as well as the spatial perception of the UUS in metro zones.Our research results provide a novel approach and theoretical basis for the development and application of UUS vitality in various cities.展开更多
This paper presents a case study of the clogging of a slurry-shield tunnel-boring machine(TBM)experienced during tunnel operations in clay-rich argillaceous siltstones under the Ganjiang River,China.The clogging exper...This paper presents a case study of the clogging of a slurry-shield tunnel-boring machine(TBM)experienced during tunnel operations in clay-rich argillaceous siltstones under the Ganjiang River,China.The clogging experienced during tunneling was due to special geological conditions,which had a considerably negative impact on the slurry-shield TBM tunneling performance.In this case study,the effect of clogging on the slurry-shield TBM tunneling performance(e.g.,advance speed,thrust,torque,and penetration per revolution)was fully investigated.The potential for clogging during tunnel operations in argillaceous siltstone was estimated using an existing empirical classification chart.Many improvement measures have been proposed to mitigate the clogging potential of two slurry-shield TBMs during tunneling,such as the use of an optimum cutting wheel,a replacement cutting tool,improvements to the circulation flushing system and slurry properties,mixed support integrating slurry,and compressed air to support the excavation face.The mechanisms and potential causes of clogging are explained in detail,and the contributions of these mitigation measures to tunneling performance are discussed.By investigating the actual operational parameters of the slurry-shield TBMs,these mitigation measures were proven to be effective in mitigating the clogging potential of slurry-shield TBMs.This case study provides valuable information for slurry-shield TBMs involving tunneling in clay-rich sedimentary rocks.展开更多
This study analyzed the passive arching effect under eccentric loading by developing a series of trapdoor discrete numerical models.The numerical models were validated by comparison with laboratory test results.The de...This study analyzed the passive arching effect under eccentric loading by developing a series of trapdoor discrete numerical models.The numerical models were validated by comparison with laboratory test results.The deformation pattern,soil arching ratio,force chain distribution,and coordination number under various surcharge magnitudes and deviation distances were analyzed.The numerical results showed that the deformation diagram of soil particles can be divided into three zones:principal displacement zone,transition zone,and static zone.With an increase in the surcharge magnitude,the range of the principal displacement zone decreased,but the range of the transition region increased.The curve of the soil arching ratio on the trapdoor can be divided into three phases,which can be well characterized by the tangent modulus.The passive arching effect is degraded by a surcharge.The ulti-mate soil arching ratio could be approximated as a W-shaped distribution along the+x-direction.With an increase in the trapdoor displacement,the force chain on the trapdoor gradually expanded outward to form an inverted funnel shape.The most powerful force on the trapdoor was mainly distributed on its edge.The average coordination number decreased gradually as the trapdoor moved upward.展开更多
The development of urban underground space(UUS)is of great significance for sustainable urban development because it has potential to solve many urban problems.However,the development of UUS is limited because there a...The development of urban underground space(UUS)is of great significance for sustainable urban development because it has potential to solve many urban problems.However,the development of UUS is limited because there are still a lot of constraints and challenges.To better understand the constraining factors of developing UUS and improve the development and utilization of UUS,this study conducts a comprehensive survey of existing literature retrieved from the Web of Science Core Collection database.Five main constraining factors,including the limited geological conditions,high cost,lack of natural light and ventilation,high incidence,and difficulty in collecting data and information on UUS,have been discussed to better understand how they affect the development of UUS.Based on the survey,the critical success factors of developing UUS,such as the effective governance structure,planning system for integrating UUS into urban development,coordination of the design of ground and underground,delineation of land property rights of UUS,and application of information techniques in the use of UUS,have been identified and discussed.In addition,knowledge gaps in the studies on development of UUS have been identified.Finally,the research trends and future directions have been proposed for better understanding and practice of UUS development.展开更多
In this study,a refined numerical model for segmental lining of a shield tunnel,which contains detailed models of reinforcement and connecting bolts,is established using finite element software.The model is first vali...In this study,a refined numerical model for segmental lining of a shield tunnel,which contains detailed models of reinforcement and connecting bolts,is established using finite element software.The model is first validated by the results from a full-scale model test.Then,based on the load-structure method,this numerical model is adopted to investigate the internal force distribution and the transverse deformation characteristics of the shield tunnel when it is subject to local soil loosening.The influence of loosening position,loosening range,and loosening extent on the mechanical response is extensively studied through comprehensive numerical analyses.The results show that the main influence of local soil loosening on the ring is to disturb the force balance and change the constraint conditions,thus changing the deformation pattern and force state.After the loosening occurs,the bending moment of the ring in the loosening range increases and the axial force decreases.The vertical convergence of the ring is the largest and the equivalent stiffness of the ring is the smallest when the local soil loosened at the haunch and the loosening range a is 90°.The vertical convergence of the ring increases with increasing of the loosening extent,and the equivalent stiffness decreases linearly with increasing of the loosening extent.The results can enhance our understanding of mechanical behaviors of segmental lining associated soil loosening,and will show a possible way for detecting soil loosening based on the measured deformation and internal forces.展开更多
Taxonomy plays an important role in understanding the origin, evolution, and ecological functionality of biodiversity. There are large number of unknown species yet to be described by taxonomists, which together with ...Taxonomy plays an important role in understanding the origin, evolution, and ecological functionality of biodiversity. There are large number of unknown species yet to be described by taxonomists, which together with their ecosystem services cannot be effectively protected prior to description. Despite this, taxonomy has been increasingly underrated insufficient funds and permanent positions to retain young talents. Further, the impact factordriven evaluation systems in China exacerbate this downward trend, so alternative evaluation metrics are urgently necessary. When the current generation of outstanding taxonomists retires,there will be too few remaining taxonomists left to train the next generation. In light of these challenges, all co-authors worked together on this paper to analyze the current situation of taxonomy and put out a joint call for immediate actions to advance taxonomy in China.展开更多
Summary What is already known about this topic?Leprosy is a chronic infectious disease that is endemic in several countries.Control of leprosy has had targets set by World Health Organization’s(WHO)Global Strategy 2...Summary What is already known about this topic?Leprosy is a chronic infectious disease that is endemic in several countries.Control of leprosy has had targets set by World Health Organization’s(WHO)Global Strategy 2016–2020 and by China through a national leprosy-control plan(2011–2020).What is added by this report?Data from the Leprosy Management Information System in China was analyzed and showed a national prevalence of 0.178 per 100,000 and detection rate of 0.037 per 100,000 residents in 2018.In addition,all the main targets for 2020 have been met by 2018 except for the proportion of counties or cities to reach a prevalence of less than 1/100,000 and the proportion of children cases with grade 2 disability(G2D).What are the implications for public health practice?There are still challenges remaining to close the gaps between current progress and the targets set forth by the WHO and China.However,lessons learned in China in developing and implementing the national program may be invaluable for future plans to achieve and sustain elimination of leprosy at global and country level.展开更多
Energy piles are a new type of heat exchange systems with buried pipes in a pile foundation,which optimize a ground source heat pump system for the utilization of shallow geothermal energy.In this study,based on the p...Energy piles are a new type of heat exchange systems with buried pipes in a pile foundation,which optimize a ground source heat pump system for the utilization of shallow geothermal energy.In this study,based on the principle of similarity,the thermo-mechanical behavior of the model energy pile with a large cross-section in saturated sandy soil was experimentally evaluated.The pre-cast model concrete pile with a diameter of 0.2 m and length of 1.5 m was buried in saturated sand in a steel box with dimensions of 2.5 m×2.5 m×2.0 m(length×width×height).The pile was heated using water in the polyethylene(PE)pipe,which was connected to a water cycle temperature controller.At a constant inlet water temperature of 55℃,three thermal cycles were carried out with the same heating and cooling periods and different water flow rates.The temperature distributions in the pile and soil,in addition to the pore pressure,soil pressure,and displacement of the pile,were monitored to clarify the thermo-mechanical behavior of the pile and soil.The heat transfer efficiency was analyzed based on the temperature difference and water flow rates.The measured strain at different locations in the pile under cyclic thermal loading revealed that the uneven strain that developed in a pile body should be considered for its long-term application.Furthermore,focus should be directed toward the long-term unrecoverable displacement of the energy pile due to the thermal plastic strain and thermal consolidation of the soil.展开更多
基金support by the National Natural Science Foundation of China(Grant Nos.52108377,52090084,and 51938008).
文摘This research explores the potential for the evaluation and prediction of earth pressure balance shield performance based on a gray system model.The research focuses on a shield tunnel excavated for Metro Line 2 in Dalian,China.Due to the large error between the initial geological exploration data and real strata,the project construction is extremely difficult.In view of the current situation regarding the project,a quantitative method for evaluating the tunneling efficiency was proposed using cutterhead rotation(R),advance speed(S),total thrust(F)and torque(T).A total of 80 datasets with three input parameters and one output variable(F or T)were collected from this project,and a prediction framework based gray system model was established.Based on the prediction model,five prediction schemes were set up.Through error analysis,the optimal prediction scheme was obtained from the five schemes.The parametric investigation performed indicates that the relationships between F and the three input variables in the gray system model harmonize with the theoretical explanation.The case shows that the shield tunneling performance and efficiency are improved by the tunneling parameter prediction model based on the gray system model.
基金support by the National Natural Science Foundation of China(Grant Nos.52108376 and 51908371)China Postdoctoral Science Foundation(Grant No.2022T150436).
文摘This paper presents a simplified elastic continuum method for calculating the restraint effect of isolation piles on tunneling-induced vertical ground displacement,which can consider not only the relative sliding of the pile‒soil interface but also the pile rowesoil interaction.The proposed method is verified by comparisons with existing theoretical methods,including the boundary element method and the elastic foundation method.The results reveal the restraining mechanism of the isolation piles on vertical ground displacements due to tunneling,i.e.the positive and negative restraint effects exerted by the isolation piles jointly drive the ground vertical displacement along the depth direction from the original tunneling-induced nonlinear variation situation to a relatively uniform situation.The results also indicate that the stiffness of the pile‒soil interface,including the pile shaft‒surrounding soil interface and pile tip-supporting soil interface,describes the strength of the pile‒soil interaction.The pile rows can confine the vertical ground displacement caused by the tunnel excavation to the inner side of the isolation piles and effectively prevent the vertical ground displacement from expanding further toward the outer side of the isolation piles.
基金funded by“The Pearl River Talent Recruitment Program”of Guangdong Province in 2019(Grant No.2019CX01G338)the Research Funding of Shantou University for New Faculty Member(Grant No.NTF19024-2019).
文摘This study presents a framework for predicting geological characteristics based on integrating a stacking classification algorithm(SCA) with a grid search(GS) and K-fold cross validation(K-CV). The SCA includes two learner layers: a primary learner’s layer and meta-classifier layer. The accuracy of the SCA can be improved by using the GS and K-CV. The GS was developed to match the hyper-parameters and optimise complicated problems. The K-CV is commonly applied to changing the validation set in a training set. In general, a GS is usually combined with K-CV to produce a corresponding evaluation index and select the best hyper-parameters. The torque penetration index(TPI) and field penetration index(FPI) are proposed based on shield parameters to express the geological characteristics. The elbow method(EM) and silhouette coefficient(Si) are employed to determine the types of geological characteristics(K) in a Kmeans++ algorithm. A case study on mixed ground in Guangzhou is adopted to validate the applicability of the developed model. The results show that with the developed framework, the four selected parameters, i.e. thrust, advance rate, cutterhead rotation speed and cutterhead torque, can be used to effectively predict the corresponding geological characteristics.
文摘It is generally recognized that Caucasians and Asians have different skin aging features.The aim of this study was to develop a facial wrinkle grading scale for Chinese women.Standard photographs were taken of 242 Chinese women.Six sets of 0 to 9 wrinkle scales with reference photographs and descriptions were selected,including grading scales for resting and hyperkinetic crow's feet,frontalis lines,glabellar frown lines,and nasolabial folds.To identify the scale by objective quantitative measurement,skin surface measurements from the Visioscan~ VC98 were used.To test the reliability and validity of our wrinkle scale,a multi-rater consensus method was used.A double-blind,randomized,vehicle-controlled 12-week study was conducted to use this clinical photo-score to evaluate the efficacy and safety of Centella triterpenes cream~ in treating crow's feet.A newly developed 10-point photographic and descriptive scale emerged from this study.The final atlas of these photographs contained a total of 6 sets with 10 pictures each.From 0 to 9,surface evaluation of smoothness(SEsm) parametric measurements decreased progressively,indicating that the scale increased inversely.Weighted kappa coefficients for intra-assessor were between 0.75-0.87.The overall Kendall's coefficient is 0.86 on the first rating and 0.87 on the second rating.Thirtysix volunteers were recruited and 35 subjects completed a 12-week trial.Clinical photo-score by investigator showed a significant difference(P < 0.05) between the treatment side and control side after 4 weeks.Use of these scales in clinical settings to evaluate facial wrinkles in Asians individuals is recommended.
基金supported by the Natural Science Research Project of Anhui Educational Committee,China(Grant No.2022AH050845)Major project of the National Natural Science Foundation of China(Grant No.52090080)+6 种基金Special project of Chinese Academy of Engineering and National Natural Science Foundation of China(Grant No.L1924061)Teaching Research Project in Anhui Province,China(Grant No.2020jyxm1819)Scientific Research Foundation for High-level Talents of Anhui University of Science and Technology,China(Grant No.2022yjrc83)Humanity and Social Science Research Project of Anhui Educational Committee,China(Grant No.SK2021A0211)Anhui Province Science and Technology Plan Project of Housing Urban-rural Construction,China(Grant Nos.2020-YF12 and 2020-YF14)Major Science and Technology Projects of Guangdong Province,China(Grant No.192019071811500001)the Research Project of Huainan Science and Technology Bureau,China(Grant No.2020141).
文摘With the rapid development of rail transit,effectively developing urban underground space(UUS)in the metro zone has become an important approach to expanding urban space.However,UUS is currently facing problems,such as an uneven distribution or even loss of vitality,which restricts the utilization efficiency of the space.Thus,we established a UUS environmental assessment system based on the‘‘comfort-aesthetic-function-traffic-structure”using space syntax,instrumental measurement,and questionnaire surveys.By constructing a partial-least-square structural equation model,the internal relationships between the UUS environment and corresponding space vitality and space perception under different study areas,namely the underground transportation-oriented space(transportation space for short)and the underground commercial-oriented space(commercial space for short),were studied in detail throughout the working day.Results indicate the following:(1)the UUS in the metro zone environment influences spatial vitality.The vitality distribution of transportation space is significantly affected by the spatial traffic and structure.The vitality distribution of commercial space is significantly affected by the spatial function and traffic.(2)The environment of UUSs in the metro zone influences users’s perception.The perception of transportation space is significantly affected by aesthetics and comfort.The perception of commercial space is significantly affected by aesthetic,comfort,and spatial functions.(3)The user’s perception affects vitality,and the effect is more significant in commercial space.This study provides an in-depth understanding of the relationship between the complex environment and its spatial vitality as well as the spatial perception of the UUS in metro zones.Our research results provide a novel approach and theoretical basis for the development and application of UUS vitality in various cities.
基金gratefully acknowledge the support of funds from the National Natural Science Foundation of China(Grant Nos.52090084,52208400).
文摘This paper presents a case study of the clogging of a slurry-shield tunnel-boring machine(TBM)experienced during tunnel operations in clay-rich argillaceous siltstones under the Ganjiang River,China.The clogging experienced during tunneling was due to special geological conditions,which had a considerably negative impact on the slurry-shield TBM tunneling performance.In this case study,the effect of clogging on the slurry-shield TBM tunneling performance(e.g.,advance speed,thrust,torque,and penetration per revolution)was fully investigated.The potential for clogging during tunnel operations in argillaceous siltstone was estimated using an existing empirical classification chart.Many improvement measures have been proposed to mitigate the clogging potential of two slurry-shield TBMs during tunneling,such as the use of an optimum cutting wheel,a replacement cutting tool,improvements to the circulation flushing system and slurry properties,mixed support integrating slurry,and compressed air to support the excavation face.The mechanisms and potential causes of clogging are explained in detail,and the contributions of these mitigation measures to tunneling performance are discussed.By investigating the actual operational parameters of the slurry-shield TBMs,these mitigation measures were proven to be effective in mitigating the clogging potential of slurry-shield TBMs.This case study provides valuable information for slurry-shield TBMs involving tunneling in clay-rich sedimentary rocks.
基金supported by the National Natural Science Foundation of China(Nos.52090081 and 51938008)Key Research and Development Program of Guangdong Province(No.2019B111105001)the Natural Science Foundation of Shenzhen(No.JCYJ20210324094607020).
文摘This study analyzed the passive arching effect under eccentric loading by developing a series of trapdoor discrete numerical models.The numerical models were validated by comparison with laboratory test results.The deformation pattern,soil arching ratio,force chain distribution,and coordination number under various surcharge magnitudes and deviation distances were analyzed.The numerical results showed that the deformation diagram of soil particles can be divided into three zones:principal displacement zone,transition zone,and static zone.With an increase in the surcharge magnitude,the range of the principal displacement zone decreased,but the range of the transition region increased.The curve of the soil arching ratio on the trapdoor can be divided into three phases,which can be well characterized by the tangent modulus.The passive arching effect is degraded by a surcharge.The ulti-mate soil arching ratio could be approximated as a W-shaped distribution along the+x-direction.With an increase in the trapdoor displacement,the force chain on the trapdoor gradually expanded outward to form an inverted funnel shape.The most powerful force on the trapdoor was mainly distributed on its edge.The average coordination number decreased gradually as the trapdoor moved upward.
基金supported by National Natural Science Foundation of China(Grant Nos.51938008 and 52090084).
文摘The development of urban underground space(UUS)is of great significance for sustainable urban development because it has potential to solve many urban problems.However,the development of UUS is limited because there are still a lot of constraints and challenges.To better understand the constraining factors of developing UUS and improve the development and utilization of UUS,this study conducts a comprehensive survey of existing literature retrieved from the Web of Science Core Collection database.Five main constraining factors,including the limited geological conditions,high cost,lack of natural light and ventilation,high incidence,and difficulty in collecting data and information on UUS,have been discussed to better understand how they affect the development of UUS.Based on the survey,the critical success factors of developing UUS,such as the effective governance structure,planning system for integrating UUS into urban development,coordination of the design of ground and underground,delineation of land property rights of UUS,and application of information techniques in the use of UUS,have been identified and discussed.In addition,knowledge gaps in the studies on development of UUS have been identified.Finally,the research trends and future directions have been proposed for better understanding and practice of UUS development.
基金the financial support provided by National Key R&D Program of China under Grant No.2018YFB2100901the National Natural Science Foundation of China under Grant Nos.51938008,52090081and China Academy of Railway Sciences Fund Project under Grand No.2019YJ181.
文摘In this study,a refined numerical model for segmental lining of a shield tunnel,which contains detailed models of reinforcement and connecting bolts,is established using finite element software.The model is first validated by the results from a full-scale model test.Then,based on the load-structure method,this numerical model is adopted to investigate the internal force distribution and the transverse deformation characteristics of the shield tunnel when it is subject to local soil loosening.The influence of loosening position,loosening range,and loosening extent on the mechanical response is extensively studied through comprehensive numerical analyses.The results show that the main influence of local soil loosening on the ring is to disturb the force balance and change the constraint conditions,thus changing the deformation pattern and force state.After the loosening occurs,the bending moment of the ring in the loosening range increases and the axial force decreases.The vertical convergence of the ring is the largest and the equivalent stiffness of the ring is the smallest when the local soil loosened at the haunch and the loosening range a is 90°.The vertical convergence of the ring increases with increasing of the loosening extent,and the equivalent stiffness decreases linearly with increasing of the loosening extent.The results can enhance our understanding of mechanical behaviors of segmental lining associated soil loosening,and will show a possible way for detecting soil loosening based on the measured deformation and internal forces.
基金mainly supported by National Science Fund for Distinguished Young Scholars (31625024)a grant (2008DP173354) from the Key Laboratory of the Zoological Systematics and Evolution of the Chinese Academy of Sciences。
文摘Taxonomy plays an important role in understanding the origin, evolution, and ecological functionality of biodiversity. There are large number of unknown species yet to be described by taxonomists, which together with their ecosystem services cannot be effectively protected prior to description. Despite this, taxonomy has been increasingly underrated insufficient funds and permanent positions to retain young talents. Further, the impact factordriven evaluation systems in China exacerbate this downward trend, so alternative evaluation metrics are urgently necessary. When the current generation of outstanding taxonomists retires,there will be too few remaining taxonomists left to train the next generation. In light of these challenges, all co-authors worked together on this paper to analyze the current situation of taxonomy and put out a joint call for immediate actions to advance taxonomy in China.
文摘Summary What is already known about this topic?Leprosy is a chronic infectious disease that is endemic in several countries.Control of leprosy has had targets set by World Health Organization’s(WHO)Global Strategy 2016–2020 and by China through a national leprosy-control plan(2011–2020).What is added by this report?Data from the Leprosy Management Information System in China was analyzed and showed a national prevalence of 0.178 per 100,000 and detection rate of 0.037 per 100,000 residents in 2018.In addition,all the main targets for 2020 have been met by 2018 except for the proportion of counties or cities to reach a prevalence of less than 1/100,000 and the proportion of children cases with grade 2 disability(G2D).What are the implications for public health practice?There are still challenges remaining to close the gaps between current progress and the targets set forth by the WHO and China.However,lessons learned in China in developing and implementing the national program may be invaluable for future plans to achieve and sustain elimination of leprosy at global and country level.
基金This work was supported by the national Natural Science Foundation of China[Grant No(s).5137215551678369]the Technical Innovation Foundation of Shenzhen[Grant No.JCYJ20170302143610976].
文摘Energy piles are a new type of heat exchange systems with buried pipes in a pile foundation,which optimize a ground source heat pump system for the utilization of shallow geothermal energy.In this study,based on the principle of similarity,the thermo-mechanical behavior of the model energy pile with a large cross-section in saturated sandy soil was experimentally evaluated.The pre-cast model concrete pile with a diameter of 0.2 m and length of 1.5 m was buried in saturated sand in a steel box with dimensions of 2.5 m×2.5 m×2.0 m(length×width×height).The pile was heated using water in the polyethylene(PE)pipe,which was connected to a water cycle temperature controller.At a constant inlet water temperature of 55℃,three thermal cycles were carried out with the same heating and cooling periods and different water flow rates.The temperature distributions in the pile and soil,in addition to the pore pressure,soil pressure,and displacement of the pile,were monitored to clarify the thermo-mechanical behavior of the pile and soil.The heat transfer efficiency was analyzed based on the temperature difference and water flow rates.The measured strain at different locations in the pile under cyclic thermal loading revealed that the uneven strain that developed in a pile body should be considered for its long-term application.Furthermore,focus should be directed toward the long-term unrecoverable displacement of the energy pile due to the thermal plastic strain and thermal consolidation of the soil.
