According to the design specifications,the construction of extended piles involves traversing the tunnel’s upper region and extending to the underlying rock layer.To address this challenge,a subterranean transfer str...According to the design specifications,the construction of extended piles involves traversing the tunnel’s upper region and extending to the underlying rock layer.To address this challenge,a subterranean transfer structure spanning multiple subway tunnels was proposed.Deliberating on the function of piles in the transfer structure as springs with axial and bending stiffness,and taking into account the force balance and deformation coordination conditions of beams and plates within the transfer structure,we established a simplified mechanical model that incorporates soil stratification by combining it with the Winkler elastic foundation beam model.The resolved established simplifiedmechanicalmodel employed finite difference technology and the Newton-Simpsonmethod,elucidating the mechanical mechanism of the transfer structure.The research findings suggest that the load carried by the upper structural columns can be transferred to the pile foundation beneath the beams through the transfer structure,subsequently reaching the deep soil layer and ensuring minimal impact on adjacent tunnels.The established simplified analysis method can be used for stress analysis of the transfer structure,concurrently considering soil stratification,pile foundation behavior,and plate action.The pile length,pile section size,and beam section size within the transfer structure should account for the characteristics of the upper load,ensuring an even distribution of the beam bending moment.展开更多
A new algorithm for the solution of quadratic programming problems is put forward in terms ofthe mixed energy theory and is further used for the incremental solution of elastic-plastic truss structures.Themethod propo...A new algorithm for the solution of quadratic programming problems is put forward in terms ofthe mixed energy theory and is further used for the incremental solution of elastic-plastic truss structures.Themethod proposed is different from the traditional one,for which the unknown variables are selected just inone class such as displacements or stresses.The present method selects the variables in the mixed form withboth displacement and stress.As the method is established in the hybrid space,the information found in theprevious incremental step can be used for the solution of the present step,making the algorithm highly effi-cient in the numerical solution process of quadratic programming problems.The results obained in the exam-ples of the elastie-plastic solution of the truss structures verify what has been predicted in the theoretical anal-ysis.展开更多
Quayside container crane is a kind of huge dimension steel structure,which is the major equipment used for handling container at modern ports.With the aim to validate the safety and reliability of the crane under seis...Quayside container crane is a kind of huge dimension steel structure,which is the major equipment used for handling container at modern ports.With the aim to validate the safety and reliability of the crane under seismic loads,besides conventional analysis,elastic-plastic time history analysis under rare seismic intensity is carried out.An ideal finite element(FEM) elastic-plastic mechanical model of the quayside container crane is presented by using ANSYS codes.Furthermore,according to elastic-plastic time history analysis theory,deformation,stress and damage pattern of the structure under rare seismic intensity are investigated.Based on the above analysis,the established reliability model according to the reliability theory,together with seismic reliability analysis based on Monte-Carlo simulation is applied to practical analysis.The results show that the overall structure of the quayside container crane is generally unstable under rare seismic intensity,and the structure needs to be reinforced.展开更多
The elastic-plastic indentation properties of materials with varying ratio of hardness to Young’s modulus(H/E) were analyzed with the finite element method. And the indentation stress fields of materials with varying...The elastic-plastic indentation properties of materials with varying ratio of hardness to Young’s modulus(H/E) were analyzed with the finite element method. And the indentation stress fields of materials with varying ratio H/E on the surface were studied by the experiment. The results show that the penetration depth, contact radius, plastic pile-up and the degree of elastic recovery depend strongly on the ratio H/E. Moreover, graphs were established to describe the relationship between the elastic-plastic indentation parameters and H/E. The established graphs can be used to predict the H/E of materials when compared with experimental data.展开更多
In this study, simplified numerical models are developed to analyze the soil-structure interaction(SSI) effect on frame structures equipped with viscoelastic dampers(VEDs) based on pile group foundation.First, a singl...In this study, simplified numerical models are developed to analyze the soil-structure interaction(SSI) effect on frame structures equipped with viscoelastic dampers(VEDs) based on pile group foundation.First, a single degree-offreedom(SDOF) oscillator is successfully utilized to replace the SDOF energy dissipated structure considering the SSI effect.The equivalent period and damping ratio of the system are obtained through analogical analysis using the frequency transfer function with adoption of the modal strain energy(MSE) technique.A parametric analysis is carried out to study the SSI effect on the performance of VEDs.Then the equilibrium equations of the multi degree-of-freedom(MDOF) structure with VEDs considering SSI effect are established in the frequency domain.Based on the assumption that the superstructure of the coupled system possesses the classical normal mode, the MDOF superstructure is decoupled to a set of individual SDOF systems resting on a rigid foundation with adoption of the MSE technique through formula derivation.Numerical results demonstrate that the proposed methods have the advantage of reducing computational cost, however, retaining the satisfactory accuracy.The numerical method proposed herein can provide a fast evaluation of the efficiency of VEDs considering the SSI effect.展开更多
In this paper, the improved near crack line analysis method proposed in Refs. [1]and [2] is used to investigate a center crack loaded by two pairs of antiplane pointforces in a finite plate in an elastic-perfectly pla...In this paper, the improved near crack line analysis method proposed in Refs. [1]and [2] is used to investigate a center crack loaded by two pairs of antiplane pointforces in a finite plate in an elastic-perfectly plastic solid. And the analytical solutionsare obtained, thai is elastic-plastic stress fields near the crack line and the taw that thelength of foe plastic zone along the crack line is varied with an external loads and thebearing capacity of a finite plate with a center crack. The results of this paper aresufficiently precise near the crack line because the assumptions of the Small scaleyielding theory have not been used and no other assumptions have been taken.展开更多
Lateral deformation of liquefiable soil is a cause of much damage during earthquakes, reportedly more than other forms of liquefaction-induced ground failures. Researchers have presented studies in which the liquefied...Lateral deformation of liquefiable soil is a cause of much damage during earthquakes, reportedly more than other forms of liquefaction-induced ground failures. Researchers have presented studies in which the liquefied soil is considered as viscous fluid. In this manner, the liquefi ed soil behaves as non-Newtonian fl uid, whose viscosity decreases as the shear strain rate increases. The current study incorporates computational fl uid dynamics to propose a simplified dynamic analysis for the liquefaction-induced lateral deformation of earth slopes. The numerical procedure involves a quasi-linear elastic model for small to moderate strains and a Bingham fluid model for large strain states during liquefaction. An iterative procedure is considered to estimate the strain-compatible shear stiffness of soil. The post-liquefaction residual strength of soil is considered as the initial Bingham viscosity. Performance of the numerical procedure is examined by using the results of centrifuge model and shaking table tests together with some field observations of lateral ground deformation. The results demonstrate that the proposed procedure predicts the time history of lateral ground deformation with a reasonable degree of precision.展开更多
Crack line field analysis method has become an independent method for crack elastic-plastic analysis, which greatly simplifies the complexity of crack elastic-plastic problems and overcomes the corresponding mathemati...Crack line field analysis method has become an independent method for crack elastic-plastic analysis, which greatly simplifies the complexity of crack elastic-plastic problems and overcomes the corresponding mathematical difficulty. With this method, the precise elastic-plastic solutions near crack lines for variety of crack problems can be obtained. But up to now all solutions obtained by this method were for different concrete problems, no general steps and no general form of matching equations near crack line are given out. With crack line analysis method, this paper proposes the general steps of elastic plastic analysis near crack line for mode I crack in elastic-perfectly plastic solids under plane stress condition, and in turn given out the solving process and result for a specific problem.展开更多
Partial least squares discriminant analysis (PLS-DA) with integrated moving-window (MW) waveband screening was applied to the discriminant analysis of liquor brands with near-infrared (NIR) spectroscopy. Luzhou Laojia...Partial least squares discriminant analysis (PLS-DA) with integrated moving-window (MW) waveband screening was applied to the discriminant analysis of liquor brands with near-infrared (NIR) spectroscopy. Luzhou Laojiao, a popular liquor with strong fragrant flavor, was used as the identified liquor brand (160 samples, negative, 52 vol alcoholicity). Liquors of 10 other brands with strong fragrant flavor were used as the interferential brands (200 samples, positive, 52 vol alcoholicity). The Kennard-Stone algorithm was used for the division of modeling samples to achieve uniformity and representativeness. Based on the MW-PLS-DA, a simplified optimal model set with 157 wavebands was further proposed. This set contained five types of wavebands corresponding to the NIR absorption bands of water, ethanol, and other micronutrients (i.e., acids, aldehydes, phenols, and aromatic compounds) in liquor for practical choice. Using five selected simple models with 4775 - 4239, 7804 - 6569, 6264 - 5844, 9435 - 7896, and 12066 - 10373 cm-1, the validation recognition rates were obtained as 99.3% or higher. Results show good prediction performance and low model complexity, and also provided a valuable reference for designing small dedicated instruments. The proposed method is a promising tool for large-scale inspection of liquor food safety.展开更多
The isolated curved girder bridge's vibration characteristics play a major part in the seismic responses of structures and anti-seismic properties.A clear analytic relationship between design parameters and the sy...The isolated curved girder bridge's vibration characteristics play a major part in the seismic responses of structures and anti-seismic properties.A clear analytic relationship between design parameters and the system's vibration characteristics could be established by its simplified dynamic analysis model,making it convenient for providing a reference to the optimization of design and safety analysis.A double-mass six-degree-of-freedom model for curved girder bridges with isolation bearings installed at the top of the bridge piers is built and a simplified analysis method for the vibration characteristics of the system is provided.Combined with the Matlab programming,the influences of radius of curvature,central angle,bridge deck width and damping ratio of the isolation layer and circular frequency of the isolation layer of isolated curved girder bridges on the pseudo-undamped natural circular frequency(called pseudo-frequency for short)and system damping ratio are systematically analyzed,and the sensitivity of vibration characteristics of isolated curved girder bridges is studied.The results show that the vibration characteristics of isolated curved girder bridges can be reflected well with this simplified model and calculation method.The pseudo-frequency of curved girder and system damping ratios increases with the increase of the isolation layer.The third-order vibration characteristic is more sensitive to the parameters of a curved girder,and the first-order vibration characteristic is sensitive to both central angle and radius of curvature to some extent while insensitive to the width of the bridge deck.Furthermore,the second-order vibration characteristic is not sensitive to the parameters of a curved girder.展开更多
By means of an asymptotic expansion method of a regular series,an exact higher-order analysis has been carried out for the near-tip fields of an in-terfacial crack between two different elastic-plastic materials. The ...By means of an asymptotic expansion method of a regular series,an exact higher-order analysis has been carried out for the near-tip fields of an in-terfacial crack between two different elastic-plastic materials. The condition of planestrain is invoked. Two group of solutions have been obtained for the crack surfaceconditions: (1) traction free and (2) frictionless contact, respectively. It is found thatalong the interface ahead of crack tip the stress fields are co-order continuous whilethe displacement fields are cross-order continuous. The zone of dominance of theasymptotic solutions has been estimated.展开更多
AIM To simplify the diagnostic criteria for superficial esophageal squamous cell carcinoma(SESCC) on Narrow Band Imaging combined with magnifying endoscopy(NBI-ME).METHODS This study was based on the post-hoc analysis...AIM To simplify the diagnostic criteria for superficial esophageal squamous cell carcinoma(SESCC) on Narrow Band Imaging combined with magnifying endoscopy(NBI-ME).METHODS This study was based on the post-hoc analysis of a randomized controlled trial. We performed NBI-ME for 147 patients with present or a history of squamous cell carcinoma in the head and neck, or esophagus between January 2009 and June 2011. Two expert endoscopistsdetected 89 lesions that were suspicious for SESCC lesions, which had been prospectively evaluated for the following 6 NBI-ME findings in real time: "intervascular background coloration"; "proliferation of intrapapillary capillary loops(IPCL)"; and "dilation", "tortuosity", "change in caliber", and "various shapes(VS)" of IPCLs(i.e., Inoue's tetrad criteria). The histologic examination of specimens was defined as the gold standard for diagnosis. A stepwise logistic regression analysis was used to identify candidates for the simplified criteria from among the 6 NBI-ME findings for diagnosing SESCCs. We evaluated diagnostic performance of the simplified criteria compared with that of Inoue's criteria.RESULTS Fifty-four lesions(65%) were histologically diagnosed as SESCCs and the others as low-grade intraepithelial neoplasia or inflammation. In the univariate analysis, proliferation, tortuosity, change in caliber, and VS were significantly associated with SESCC(P < 0.01). The combination of VS and proliferation was statistically extracted from the 6 NBI-ME findings by using the stepwise logistic regression model. We defined the combination of VS and proliferation as simplified dyad criteria for SESCC. The areas under the curve of the simplified dyad criteria and Inoue's tetrad criteria were 0.70 and 0.73, respectively. No significant difference was shown between them. The sensitivity, specificity, and accuracy of diagnosis for SESCC were 77.8%, 57.1%, 69.7% and 51.9%, 80.0%, 62.9% for the simplified dyad criteria and Inoue's tetrad criteria, respectively.CONCLUSION The combination of proliferation and VS may serve as simplified criteria for the diagnosis of SESCC using NBIME.展开更多
The existing theories for closed loop identification with the linear feedback controller are very mature.To apply the existed theories directly in the control field,we propose a new idea about replacing the original u...The existing theories for closed loop identification with the linear feedback controller are very mature.To apply the existed theories directly in the control field,we propose a new idea about replacing the original unknown and nonlinear feedback controller with one approximated linear controller,while guaranteeing the equivalent property for the obtained closed loop system.Based on some statistical correlation functions,one condition is derived to show the equivalent property between the approximated linear controller and the original nonlinear controller.The detailed explicit form,corresponding to the approximated linear controller,is also constructed.Furthermore,to give a complete analysis for closed loop identification,the cost function is rewritten as one extended expression,being convenient to understand.Then spectral estimation is introduced to identify the unknown plant in the closed loop system.Finally,the proposed theories are verified by one simulation example.展开更多
The simplified D&L method with special properties required by ideal decomposition method was used to decompose the impact of carbon emission intensity,input-output technology,the final demand structure and the fin...The simplified D&L method with special properties required by ideal decomposition method was used to decompose the impact of carbon emission intensity,input-output technology,the final demand structure and the final demand level on changes in industrial carbon emissions in China during 1997-2012. The results showed that the final demand level which was the most important factor leading to the growth of carbon emissions performed a steadily and significantly positive and sustained effect. The carbon emissions intensity which was the only factor that led to the reduction in carbon emissions showed a negative effect. The input-output technology showed a positive effect. The final demand structure underwent a transition from a negative effect to a weak positive effect and finally to a positive effect. In order to achieve the goal of total carbon emission control,China should take some measures such as reducing direct carbon emission coefficient to strengthen the negative impact of carbon emission intensity. Meanwhile,China should implement some structural adjustment measures such as optimizing the final demand structure and reducing the proportion of industries with a great increase of influence coefficient to change the input-output technology and the final demand structure from the positive effect to the negative effect.展开更多
基金supported by the Construction and Scientific Research Project of the Zhejiang Provincial Department of Housing and Urban-Rural Development(No.2021K126,Granted byM.J.,Long,URL:https://jst.zj.gov.cn/)the ScientificResearch Project of ChinaConstruction 4th Engineering Bureau(No.CSCEC4B-2022-KTA-10,Granted by Z.C.,Bai,URL:https://4 bur.cscec.com/)+2 种基金the Scientific Research Project of China Construction 4th Engineering Bureau(No.CSCEC4B-2023-KTA-10,Granted by D.J.,Geng,URL:https://4bur.cscec.com/)the Natural Science Foundation of Hubei Province(No.2022CFD055,Granted by N.,Dai,URL:https://kjt.hubei.gov.cn/)the National Key Research and Development Program of China under Grant No.2022YFC3803002.
文摘According to the design specifications,the construction of extended piles involves traversing the tunnel’s upper region and extending to the underlying rock layer.To address this challenge,a subterranean transfer structure spanning multiple subway tunnels was proposed.Deliberating on the function of piles in the transfer structure as springs with axial and bending stiffness,and taking into account the force balance and deformation coordination conditions of beams and plates within the transfer structure,we established a simplified mechanical model that incorporates soil stratification by combining it with the Winkler elastic foundation beam model.The resolved established simplifiedmechanicalmodel employed finite difference technology and the Newton-Simpsonmethod,elucidating the mechanical mechanism of the transfer structure.The research findings suggest that the load carried by the upper structural columns can be transferred to the pile foundation beneath the beams through the transfer structure,subsequently reaching the deep soil layer and ensuring minimal impact on adjacent tunnels.The established simplified analysis method can be used for stress analysis of the transfer structure,concurrently considering soil stratification,pile foundation behavior,and plate action.The pile length,pile section size,and beam section size within the transfer structure should account for the characteristics of the upper load,ensuring an even distribution of the beam bending moment.
基金the National Natural Science Foundation of China(No.50178916,No.19732020 and No.19872016)the National Key Basic lteseareh Special Foundation(No.G1999032805)+1 种基金the Special Funds for Major State Basic Researeh Projectsthe Foundation for University Key Teachers by the Ministry of Education of China
文摘A new algorithm for the solution of quadratic programming problems is put forward in terms ofthe mixed energy theory and is further used for the incremental solution of elastic-plastic truss structures.Themethod proposed is different from the traditional one,for which the unknown variables are selected just inone class such as displacements or stresses.The present method selects the variables in the mixed form withboth displacement and stress.As the method is established in the hybrid space,the information found in theprevious incremental step can be used for the solution of the present step,making the algorithm highly effi-cient in the numerical solution process of quadratic programming problems.The results obained in the exam-ples of the elastie-plastic solution of the truss structures verify what has been predicted in the theoretical anal-ysis.
基金supported by National High Technology Research and Development Program 863 Plan (No. 2009AA043000)
文摘Quayside container crane is a kind of huge dimension steel structure,which is the major equipment used for handling container at modern ports.With the aim to validate the safety and reliability of the crane under seismic loads,besides conventional analysis,elastic-plastic time history analysis under rare seismic intensity is carried out.An ideal finite element(FEM) elastic-plastic mechanical model of the quayside container crane is presented by using ANSYS codes.Furthermore,according to elastic-plastic time history analysis theory,deformation,stress and damage pattern of the structure under rare seismic intensity are investigated.Based on the above analysis,the established reliability model according to the reliability theory,together with seismic reliability analysis based on Monte-Carlo simulation is applied to practical analysis.The results show that the overall structure of the quayside container crane is generally unstable under rare seismic intensity,and the structure needs to be reinforced.
基金Science Research Foundation of Shanghai Municipal Education Commission (No.06VZ004)
文摘The elastic-plastic indentation properties of materials with varying ratio of hardness to Young’s modulus(H/E) were analyzed with the finite element method. And the indentation stress fields of materials with varying ratio H/E on the surface were studied by the experiment. The results show that the penetration depth, contact radius, plastic pile-up and the degree of elastic recovery depend strongly on the ratio H/E. Moreover, graphs were established to describe the relationship between the elastic-plastic indentation parameters and H/E. The established graphs can be used to predict the H/E of materials when compared with experimental data.
基金National Natural Science Foundation of China under Grant Nos.51678302 and 51678301Jiangsu Province Industry-University-Research Joint Innovation Fund--Prospective Joint Research Project under Grant No.BY2014005-05Major Program of Natural Science Foundation of the Jiangsu Higher Education Institutions of China under Grant No.14KJA560001
文摘In this study, simplified numerical models are developed to analyze the soil-structure interaction(SSI) effect on frame structures equipped with viscoelastic dampers(VEDs) based on pile group foundation.First, a single degree-offreedom(SDOF) oscillator is successfully utilized to replace the SDOF energy dissipated structure considering the SSI effect.The equivalent period and damping ratio of the system are obtained through analogical analysis using the frequency transfer function with adoption of the modal strain energy(MSE) technique.A parametric analysis is carried out to study the SSI effect on the performance of VEDs.Then the equilibrium equations of the multi degree-of-freedom(MDOF) structure with VEDs considering SSI effect are established in the frequency domain.Based on the assumption that the superstructure of the coupled system possesses the classical normal mode, the MDOF superstructure is decoupled to a set of individual SDOF systems resting on a rigid foundation with adoption of the MSE technique through formula derivation.Numerical results demonstrate that the proposed methods have the advantage of reducing computational cost, however, retaining the satisfactory accuracy.The numerical method proposed herein can provide a fast evaluation of the efficiency of VEDs considering the SSI effect.
文摘In this paper, the improved near crack line analysis method proposed in Refs. [1]and [2] is used to investigate a center crack loaded by two pairs of antiplane pointforces in a finite plate in an elastic-perfectly plastic solid. And the analytical solutionsare obtained, thai is elastic-plastic stress fields near the crack line and the taw that thelength of foe plastic zone along the crack line is varied with an external loads and thebearing capacity of a finite plate with a center crack. The results of this paper aresufficiently precise near the crack line because the assumptions of the Small scaleyielding theory have not been used and no other assumptions have been taken.
基金International Institute of Earthquake Engineering and Seismology(IIEES)under Grant No.AM-7/507-6 723-545
文摘Lateral deformation of liquefiable soil is a cause of much damage during earthquakes, reportedly more than other forms of liquefaction-induced ground failures. Researchers have presented studies in which the liquefied soil is considered as viscous fluid. In this manner, the liquefi ed soil behaves as non-Newtonian fl uid, whose viscosity decreases as the shear strain rate increases. The current study incorporates computational fl uid dynamics to propose a simplified dynamic analysis for the liquefaction-induced lateral deformation of earth slopes. The numerical procedure involves a quasi-linear elastic model for small to moderate strains and a Bingham fluid model for large strain states during liquefaction. An iterative procedure is considered to estimate the strain-compatible shear stiffness of soil. The post-liquefaction residual strength of soil is considered as the initial Bingham viscosity. Performance of the numerical procedure is examined by using the results of centrifuge model and shaking table tests together with some field observations of lateral ground deformation. The results demonstrate that the proposed procedure predicts the time history of lateral ground deformation with a reasonable degree of precision.
文摘Crack line field analysis method has become an independent method for crack elastic-plastic analysis, which greatly simplifies the complexity of crack elastic-plastic problems and overcomes the corresponding mathematical difficulty. With this method, the precise elastic-plastic solutions near crack lines for variety of crack problems can be obtained. But up to now all solutions obtained by this method were for different concrete problems, no general steps and no general form of matching equations near crack line are given out. With crack line analysis method, this paper proposes the general steps of elastic plastic analysis near crack line for mode I crack in elastic-perfectly plastic solids under plane stress condition, and in turn given out the solving process and result for a specific problem.
文摘Partial least squares discriminant analysis (PLS-DA) with integrated moving-window (MW) waveband screening was applied to the discriminant analysis of liquor brands with near-infrared (NIR) spectroscopy. Luzhou Laojiao, a popular liquor with strong fragrant flavor, was used as the identified liquor brand (160 samples, negative, 52 vol alcoholicity). Liquors of 10 other brands with strong fragrant flavor were used as the interferential brands (200 samples, positive, 52 vol alcoholicity). The Kennard-Stone algorithm was used for the division of modeling samples to achieve uniformity and representativeness. Based on the MW-PLS-DA, a simplified optimal model set with 157 wavebands was further proposed. This set contained five types of wavebands corresponding to the NIR absorption bands of water, ethanol, and other micronutrients (i.e., acids, aldehydes, phenols, and aromatic compounds) in liquor for practical choice. Using five selected simple models with 4775 - 4239, 7804 - 6569, 6264 - 5844, 9435 - 7896, and 12066 - 10373 cm-1, the validation recognition rates were obtained as 99.3% or higher. Results show good prediction performance and low model complexity, and also provided a valuable reference for designing small dedicated instruments. The proposed method is a promising tool for large-scale inspection of liquor food safety.
基金This work was financially supported by National Natural Science Foundation of China through Grant 51778471Scientific Project of Education Department of Jiangxi Province GJJ160620Science and Technology Project of Communications Department of Jiangxi Province 2016C0006.
文摘The isolated curved girder bridge's vibration characteristics play a major part in the seismic responses of structures and anti-seismic properties.A clear analytic relationship between design parameters and the system's vibration characteristics could be established by its simplified dynamic analysis model,making it convenient for providing a reference to the optimization of design and safety analysis.A double-mass six-degree-of-freedom model for curved girder bridges with isolation bearings installed at the top of the bridge piers is built and a simplified analysis method for the vibration characteristics of the system is provided.Combined with the Matlab programming,the influences of radius of curvature,central angle,bridge deck width and damping ratio of the isolation layer and circular frequency of the isolation layer of isolated curved girder bridges on the pseudo-undamped natural circular frequency(called pseudo-frequency for short)and system damping ratio are systematically analyzed,and the sensitivity of vibration characteristics of isolated curved girder bridges is studied.The results show that the vibration characteristics of isolated curved girder bridges can be reflected well with this simplified model and calculation method.The pseudo-frequency of curved girder and system damping ratios increases with the increase of the isolation layer.The third-order vibration characteristic is more sensitive to the parameters of a curved girder,and the first-order vibration characteristic is sensitive to both central angle and radius of curvature to some extent while insensitive to the width of the bridge deck.Furthermore,the second-order vibration characteristic is not sensitive to the parameters of a curved girder.
基金The project supported by the National Natural Science Foundation of China
文摘By means of an asymptotic expansion method of a regular series,an exact higher-order analysis has been carried out for the near-tip fields of an in-terfacial crack between two different elastic-plastic materials. The condition of planestrain is invoked. Two group of solutions have been obtained for the crack surfaceconditions: (1) traction free and (2) frictionless contact, respectively. It is found thatalong the interface ahead of crack tip the stress fields are co-order continuous whilethe displacement fields are cross-order continuous. The zone of dominance of theasymptotic solutions has been estimated.
文摘AIM To simplify the diagnostic criteria for superficial esophageal squamous cell carcinoma(SESCC) on Narrow Band Imaging combined with magnifying endoscopy(NBI-ME).METHODS This study was based on the post-hoc analysis of a randomized controlled trial. We performed NBI-ME for 147 patients with present or a history of squamous cell carcinoma in the head and neck, or esophagus between January 2009 and June 2011. Two expert endoscopistsdetected 89 lesions that were suspicious for SESCC lesions, which had been prospectively evaluated for the following 6 NBI-ME findings in real time: "intervascular background coloration"; "proliferation of intrapapillary capillary loops(IPCL)"; and "dilation", "tortuosity", "change in caliber", and "various shapes(VS)" of IPCLs(i.e., Inoue's tetrad criteria). The histologic examination of specimens was defined as the gold standard for diagnosis. A stepwise logistic regression analysis was used to identify candidates for the simplified criteria from among the 6 NBI-ME findings for diagnosing SESCCs. We evaluated diagnostic performance of the simplified criteria compared with that of Inoue's criteria.RESULTS Fifty-four lesions(65%) were histologically diagnosed as SESCCs and the others as low-grade intraepithelial neoplasia or inflammation. In the univariate analysis, proliferation, tortuosity, change in caliber, and VS were significantly associated with SESCC(P < 0.01). The combination of VS and proliferation was statistically extracted from the 6 NBI-ME findings by using the stepwise logistic regression model. We defined the combination of VS and proliferation as simplified dyad criteria for SESCC. The areas under the curve of the simplified dyad criteria and Inoue's tetrad criteria were 0.70 and 0.73, respectively. No significant difference was shown between them. The sensitivity, specificity, and accuracy of diagnosis for SESCC were 77.8%, 57.1%, 69.7% and 51.9%, 80.0%, 62.9% for the simplified dyad criteria and Inoue's tetrad criteria, respectively.CONCLUSION The combination of proliferation and VS may serve as simplified criteria for the diagnosis of SESCC using NBIME.
文摘The existing theories for closed loop identification with the linear feedback controller are very mature.To apply the existed theories directly in the control field,we propose a new idea about replacing the original unknown and nonlinear feedback controller with one approximated linear controller,while guaranteeing the equivalent property for the obtained closed loop system.Based on some statistical correlation functions,one condition is derived to show the equivalent property between the approximated linear controller and the original nonlinear controller.The detailed explicit form,corresponding to the approximated linear controller,is also constructed.Furthermore,to give a complete analysis for closed loop identification,the cost function is rewritten as one extended expression,being convenient to understand.Then spectral estimation is introduced to identify the unknown plant in the closed loop system.Finally,the proposed theories are verified by one simulation example.
基金Supported by General Project for Humanities and Social Sciences Research of Ministry of Education of China(10YJC790025)Philosophy and Social Sciences Planning Project of Zhejiang Province(10CGJJ12YBQ)
文摘The simplified D&L method with special properties required by ideal decomposition method was used to decompose the impact of carbon emission intensity,input-output technology,the final demand structure and the final demand level on changes in industrial carbon emissions in China during 1997-2012. The results showed that the final demand level which was the most important factor leading to the growth of carbon emissions performed a steadily and significantly positive and sustained effect. The carbon emissions intensity which was the only factor that led to the reduction in carbon emissions showed a negative effect. The input-output technology showed a positive effect. The final demand structure underwent a transition from a negative effect to a weak positive effect and finally to a positive effect. In order to achieve the goal of total carbon emission control,China should take some measures such as reducing direct carbon emission coefficient to strengthen the negative impact of carbon emission intensity. Meanwhile,China should implement some structural adjustment measures such as optimizing the final demand structure and reducing the proportion of industries with a great increase of influence coefficient to change the input-output technology and the final demand structure from the positive effect to the negative effect.