In this paper,a research was conducted on the design technology of continuous beam-arch composite bridges.A brief introduction is given on the of continuous beam-arch composite bridges,its basic mechanical characteris...In this paper,a research was conducted on the design technology of continuous beam-arch composite bridges.A brief introduction is given on the of continuous beam-arch composite bridges,its basic mechanical characteristics is analyzed,and three aspects of design technology is studied,which are rise-span ratio,stiffness ratio,and bridge deck cracking.This article acts as a reference for relevant design units in China to improve the design of continuous beam-arch combination bridges.展开更多
This study was conducted with non-English sophomore students,aiming to explore the effects of different interaction combinations and language levels on continuous writing in an online environment,and compare the diffe...This study was conducted with non-English sophomore students,aiming to explore the effects of different interaction combinations and language levels on continuous writing in an online environment,and compare the differences in lexical alignments and composition quality of learners with different interaction combinations and language levels in the same continuous writing task through experiments.The results show that the mean values of the word-phrase alignment of the paired group were higher than those of the individual group in different interaction combinations,and the two groups showed significant differences;in terms of composition quality,the individual group was better than the paired group,but there was no significant difference between the two groups in terms of task continuation.Secondly,the word-phrase alignment and composition scores of the different language-level groups were higher than those of the same language-level groups,and there was a significant difference between the two groups in terms of word-phrase alignments,but not in terms of composition scores.The results of this study can be useful and informative for second language teachers in future continuous teaching in online environments.展开更多
Recovery of the coal buried under buildings,railways and water bodies and the residual coal in irregularly arranged fully mechanized mining faces is a common engineering problem facing underground coal mining.In this ...Recovery of the coal buried under buildings,railways and water bodies and the residual coal in irregularly arranged fully mechanized mining faces is a common engineering problem facing underground coal mining.In this study,a mining technology of continuous driving and gangue backfilling(CDGB)was proposed.The technology,which can not only alleviate ground subsidence and gangue discharge,but also release the above-mentioned coals,contributes to green and efficient sustainable development of mining.The stability of the system of the solidified body-reserved coal pillar combination(S-C combination)is crucial to the CDGB technology.Therefore,it is of great significance to explore the mechanical and damage characteristics of S-C combination in the synergistic bearing process.First,four sets of differentshaped S-C combination specimens were fabricated and a S-C combination bearing structure in CDGB was constructed to explore the differences in mechanical characteristics and damage modes of different-shaped S-C combination specimens during CDGB.Subsequently,their surface strain field evolutions and acoustic emission(AE)response characteristics in the load-bearing process were obtained with the aid of the digital image correlation technique and the AE signal monitoring system.Furthermore,a damage evolution model based on AE parameters and mechanical parameters was established to clarify the damage evolution law.The following results were obtained:(1)The free area of S-C combination can serve as a quantitative index to evaluate the stability of the overburden control system;(2)The concept of critical value k of the free area was first proposed.When the free area exceeds the critical value k(free area ratio greater than 1.13),the deformation resistance and the free area changes becomes negatively correlated;(3)As the free area expands,the failure of the S-C combination specimen evolves from tensile failure to shear failure.The distribution characteristics of the axial strain field also verified such a change in the failure mode;(4)When the free area expands,the peak AE count gradually changes from“double peaks”to“a single peak”.In this process,the expansion of free area shortens the time for accumulating and releasing energy during loading.Micro cracks generated in the specimen change from a phased steep growth to a continuous increase,and the process in which micro cracks develop,converge,intersect and connect to form macro cracks accelerates.The damage evolution law concluded based on AE parameters and mechanical parameters can well characterize the damage evolution process of S-C combination,providing certain reference for the study on the synergistic bearing of S-C combination during CDGB.展开更多
The paper summarizes the four different construction schemes based on engineering cases for the arch rib construction of continuous beam-arch composite bridges for high-speed railways.These methods include in-situ ass...The paper summarizes the four different construction schemes based on engineering cases for the arch rib construction of continuous beam-arch composite bridges for high-speed railways.These methods include in-situ assembly,segmental lifting,incremental launching and longitudinal moving,and vertical rotation.The temporary structural designs,process methods,and technological equipment for each construction scheme are described in detail.The advantages and disadvantages of each scheme and its application scope under various conditions are analyzed,and opinions and suggestions for guiding the application of each scheme are proposed.The comparison and selection analyses show that the four arch rib construction schemes have certain applicability under different conditions such as bridge site status,bridge span,and construction environment.With the continuous increase of bridge span and progress of construction technological equipment,the arch rib construction technology is developing towards the overall erection direction.This leads to more obvious technical advantages of the segmental lifting method,incremental launching and longitudinal moving method,and vertical rotation method.Therefore,it is necessary to select the best construction scheme according to the construction status and technical conditions during application.展开更多
To determine the extrusion force of pipe fabricated by continuous casting and extrusion (CASTEX) using an expansion combination die, the metallic expansion combination die was divided into diversion zone, expansion zo...To determine the extrusion force of pipe fabricated by continuous casting and extrusion (CASTEX) using an expansion combination die, the metallic expansion combination die was divided into diversion zone, expansion zone, flow dividing zone, welding chamber, and sizing zone, and the corresponding stress formulae in various zones were established using the slab method. The deformation zones of CASTEX groove were divided into liquid and semisolid zone, solid primary gripping zone, and solid gripping zone, and the formulae of pipe extrusion forces were established. Experiments were carried out on the self-designed CASTEX machine to obtain the aluminum pipe and measure its extrusion force using the expansion combination die. The experimental results of radial extrusion force for aluminum pipe are in good agreement with the calculated ones.展开更多
Continuous System Simulation (CSS) is a powerful way to study the behaviour of differential-algebraic equation models. Differential-algebraic equation modelling goes back to Newton and works well for models of e.g. ph...Continuous System Simulation (CSS) is a powerful way to study the behaviour of differential-algebraic equation models. Differential-algebraic equation modelling goes back to Newton and works well for models of e.g. physical systems where stochasticity plays almost no role, and where only a single attribute of an object is studied over time. However, when results from a deterministic CSS model are compared with results from a Discrete Event Simulation (DES) model, they are often inconsistent. The reasons behind this CSS-DES inconsistency are nowadays well understood. In this paper, we demonstrate that a CSS model can contain both continuous state variables (compartments) that change continuously over time and discrete state variables (also compartments) that model discrete entities and change by integer amounts. In both cases, the time-slicing method is used to advance time. Furthermore, stochasticity can and should play the same role in CSS as it does in DES. This paper first explains how a well-defined conceptual model can be stepwise transformed in a consistent way into a CSS model. These transformation steps provide insights into how to construct a consistent CSS model. In short, this is about preserving uncertainties, attributes and dynamic properties. An additional benefit of this approach is that continuous and discrete sub-models can interact within the same model, without having to combine different types of simulation languages, types of time handling and incongruent concepts. To facilitate the use and understanding of stochastic CSS, this paper is also intended to serve as a guide to performing consistent CSS modelling and simulation. Furthermore, an open source tool for collecting and analyzing the outputs from a stochastic CSS model and analyzing and presenting the results in statistical form is also developed and made available to the reader.展开更多
文摘In this paper,a research was conducted on the design technology of continuous beam-arch composite bridges.A brief introduction is given on the of continuous beam-arch composite bridges,its basic mechanical characteristics is analyzed,and three aspects of design technology is studied,which are rise-span ratio,stiffness ratio,and bridge deck cracking.This article acts as a reference for relevant design units in China to improve the design of continuous beam-arch combination bridges.
文摘This study was conducted with non-English sophomore students,aiming to explore the effects of different interaction combinations and language levels on continuous writing in an online environment,and compare the differences in lexical alignments and composition quality of learners with different interaction combinations and language levels in the same continuous writing task through experiments.The results show that the mean values of the word-phrase alignment of the paired group were higher than those of the individual group in different interaction combinations,and the two groups showed significant differences;in terms of composition quality,the individual group was better than the paired group,but there was no significant difference between the two groups in terms of task continuation.Secondly,the word-phrase alignment and composition scores of the different language-level groups were higher than those of the same language-level groups,and there was a significant difference between the two groups in terms of word-phrase alignments,but not in terms of composition scores.The results of this study can be useful and informative for second language teachers in future continuous teaching in online environments.
基金the National Natural Science Foundation of China(Nos.U21A20108,52322403,52174108,and 51974105)the Support Plan for Science&Technology Innovation Talents in Universities of Henan Province(No.21HASTIT024)+1 种基金the Scientific and technological innovation research team of Henan Polytechnic University(No.T2021-5)the Henan Excellent Youth Science Foundation(No.222300420045).
文摘Recovery of the coal buried under buildings,railways and water bodies and the residual coal in irregularly arranged fully mechanized mining faces is a common engineering problem facing underground coal mining.In this study,a mining technology of continuous driving and gangue backfilling(CDGB)was proposed.The technology,which can not only alleviate ground subsidence and gangue discharge,but also release the above-mentioned coals,contributes to green and efficient sustainable development of mining.The stability of the system of the solidified body-reserved coal pillar combination(S-C combination)is crucial to the CDGB technology.Therefore,it is of great significance to explore the mechanical and damage characteristics of S-C combination in the synergistic bearing process.First,four sets of differentshaped S-C combination specimens were fabricated and a S-C combination bearing structure in CDGB was constructed to explore the differences in mechanical characteristics and damage modes of different-shaped S-C combination specimens during CDGB.Subsequently,their surface strain field evolutions and acoustic emission(AE)response characteristics in the load-bearing process were obtained with the aid of the digital image correlation technique and the AE signal monitoring system.Furthermore,a damage evolution model based on AE parameters and mechanical parameters was established to clarify the damage evolution law.The following results were obtained:(1)The free area of S-C combination can serve as a quantitative index to evaluate the stability of the overburden control system;(2)The concept of critical value k of the free area was first proposed.When the free area exceeds the critical value k(free area ratio greater than 1.13),the deformation resistance and the free area changes becomes negatively correlated;(3)As the free area expands,the failure of the S-C combination specimen evolves from tensile failure to shear failure.The distribution characteristics of the axial strain field also verified such a change in the failure mode;(4)When the free area expands,the peak AE count gradually changes from“double peaks”to“a single peak”.In this process,the expansion of free area shortens the time for accumulating and releasing energy during loading.Micro cracks generated in the specimen change from a phased steep growth to a continuous increase,and the process in which micro cracks develop,converge,intersect and connect to form macro cracks accelerates.The damage evolution law concluded based on AE parameters and mechanical parameters can well characterize the damage evolution process of S-C combination,providing certain reference for the study on the synergistic bearing of S-C combination during CDGB.
文摘The paper summarizes the four different construction schemes based on engineering cases for the arch rib construction of continuous beam-arch composite bridges for high-speed railways.These methods include in-situ assembly,segmental lifting,incremental launching and longitudinal moving,and vertical rotation.The temporary structural designs,process methods,and technological equipment for each construction scheme are described in detail.The advantages and disadvantages of each scheme and its application scope under various conditions are analyzed,and opinions and suggestions for guiding the application of each scheme are proposed.The comparison and selection analyses show that the four arch rib construction schemes have certain applicability under different conditions such as bridge site status,bridge span,and construction environment.With the continuous increase of bridge span and progress of construction technological equipment,the arch rib construction technology is developing towards the overall erection direction.This leads to more obvious technical advantages of the segmental lifting method,incremental launching and longitudinal moving method,and vertical rotation method.Therefore,it is necessary to select the best construction scheme according to the construction status and technical conditions during application.
基金Projects(51334006,50274020)supported by the National Natural Science Foundation of China
文摘To determine the extrusion force of pipe fabricated by continuous casting and extrusion (CASTEX) using an expansion combination die, the metallic expansion combination die was divided into diversion zone, expansion zone, flow dividing zone, welding chamber, and sizing zone, and the corresponding stress formulae in various zones were established using the slab method. The deformation zones of CASTEX groove were divided into liquid and semisolid zone, solid primary gripping zone, and solid gripping zone, and the formulae of pipe extrusion forces were established. Experiments were carried out on the self-designed CASTEX machine to obtain the aluminum pipe and measure its extrusion force using the expansion combination die. The experimental results of radial extrusion force for aluminum pipe are in good agreement with the calculated ones.
文摘Continuous System Simulation (CSS) is a powerful way to study the behaviour of differential-algebraic equation models. Differential-algebraic equation modelling goes back to Newton and works well for models of e.g. physical systems where stochasticity plays almost no role, and where only a single attribute of an object is studied over time. However, when results from a deterministic CSS model are compared with results from a Discrete Event Simulation (DES) model, they are often inconsistent. The reasons behind this CSS-DES inconsistency are nowadays well understood. In this paper, we demonstrate that a CSS model can contain both continuous state variables (compartments) that change continuously over time and discrete state variables (also compartments) that model discrete entities and change by integer amounts. In both cases, the time-slicing method is used to advance time. Furthermore, stochasticity can and should play the same role in CSS as it does in DES. This paper first explains how a well-defined conceptual model can be stepwise transformed in a consistent way into a CSS model. These transformation steps provide insights into how to construct a consistent CSS model. In short, this is about preserving uncertainties, attributes and dynamic properties. An additional benefit of this approach is that continuous and discrete sub-models can interact within the same model, without having to combine different types of simulation languages, types of time handling and incongruent concepts. To facilitate the use and understanding of stochastic CSS, this paper is also intended to serve as a guide to performing consistent CSS modelling and simulation. Furthermore, an open source tool for collecting and analyzing the outputs from a stochastic CSS model and analyzing and presenting the results in statistical form is also developed and made available to the reader.
