A recent seismic event was recorded by a deep longwall mine in Virginia at 3.7 ML on the local magnitude scale and 3.4 MMS by the United States Geological Survey(USGS) in 2016.Further investigations by the National In...A recent seismic event was recorded by a deep longwall mine in Virginia at 3.7 ML on the local magnitude scale and 3.4 MMS by the United States Geological Survey(USGS) in 2016.Further investigations by the National Institute for Occupational Safety and Health(NIOSH) and Coronado Coal researchers have shown that this event was associated with geological features that have also been associated with other, similar seismic events in Virginia.Detailed mapping and geological exploration in the mining area has made it possible to forecast possible locations for future seismic activity.In order to use the geology as a forecaster of mining-induced seismic events and their energy potential, two primary components are needed.The first component is a long history of recorded seismic events with accurately plotted locations.The second component is a high density of geologic data within the mining area.In this case, 181 events of 1.0 MLor greater were recorded by the mine's seismic network between January, 2009, and October, 2016.Within the mining area, 897 geophysical logs, 224 core holes, and 1031 fiberscope holes were examined by mine geologists.From this information, it was found that overburden thickness, sandstone thickness, and sandstone quality contributed greatly to seismic locations.After the data was analyzed, a pattern became apparent indicating that the majority of seismic events occurred under specific conditions.Three forecast maps were created based on geology of previous seismic locations.The forecast maps have shown an accuracy of within 74%–89% when compared to the recorded 181 events that were1.0 MLor greater when considering three major geological criteria of overburden thickness of 579.12 m or greater, 6.096–12.192 m of sandstone within 15.24 m of the Pocahontas number 3 seam, and a longwall caving height of 4.572 m or less.展开更多
In order to assess Stathmin as an immunohistochemical(IHC)indicator of phosphatidylinositol 3-kinase(PI3K)pathway activity in HPV-negative head&neck squamous cell carcinoma(HNSCC),we compared Stathmin IHC to expre...In order to assess Stathmin as an immunohistochemical(IHC)indicator of phosphatidylinositol 3-kinase(PI3K)pathway activity in HPV-negative head&neck squamous cell carcinoma(HNSCC),we compared Stathmin IHC to expression of other pathway components.We also evaluated the relationship between Stathmin IHC and the mutational status of four key pathway genes.Finally,we ascertained whether Stathmin IHC correlates with tumor grade or primary site.Correlation exists between high Stathmin expression and high pAKT1 expression,indicating a role for Stathmin IHC as a marker of pathway activity.Our analysis did not show correlation between Stathmin IHC and mutation of the four genes evaluated.We also observed an association between high Stathmin expression and oropharyngeal primary site.Our results suggest utility of Stathmin IHC as an indicator of PI3K pathway activity,and thereby demonstrate potential relevance of Stathmin IHC in the context,of HNSCC.展开更多
A developmental research has been carried out to deal with the high performance of Cu-Cr-Zr-Mg lead frame alloy by artificial neural network (ANN). Using the cold working to assist in the aging hardening can improve t...A developmental research has been carried out to deal with the high performance of Cu-Cr-Zr-Mg lead frame alloy by artificial neural network (ANN). Using the cold working to assist in the aging hardening can improve the the hardness and electrical conductivity properties of Cu-Cr-Zr-Mg lead frame alloy. This paper studies the effect of different extent of cold working on the aging properties by a supervised ANN to model the non-linear relationship between processing parameters and the properties. The back-propagation (BP) training algorithm is improved by Levenberg-Marquardt algorithm. A basic repository on the domain knowledge of cold worked aging processes is established via sufficient data mining by the network. The predicted values of the ANN coincide well with the tested data. So an important foundation has been laid for prediction and optimum controlling the rolling and aging properties of Cu-Cr-Zr-Mg alloy.展开更多
This paper presents the results of a unique study conducted by the National Institute for Occupational Safety and Health(NIOSH)from 2016 to 2019 to evaluate the effects of longwall-induced subsurface deformations on s...This paper presents the results of a unique study conducted by the National Institute for Occupational Safety and Health(NIOSH)from 2016 to 2019 to evaluate the effects of longwall-induced subsurface deformations on shale gas well casing integrity and underground miner safety and health.At both deep-cover and shallow-cover instrumentation sites,surface subsidence measurements,subsurface inplace inclinometer measurements,and underground pillar pressure measurements were conducted as longwall panels were mined.Comparisons of the deep-cover and shallow-cover test site results with those from a similar study under medium cover reveal an interesting longwall-induced response scenario.Under shallow and medium covers,measured horizontal displacements within the abutment pillar are one order of magnitude higher than those measured under deep cover.On the other hand,measured vertical compressions under deep cover are one order of magnitude higher than those under shallow and medium covers.However,FLAC3 Dsimulations of the casings indicate that,in all three cases,the P-110 production casings remain intact under longwall-induced deformations and compressions,which has serious implications for future mine design in areas where shale gas wells have been drilled ahead of mining.展开更多
Striving to peak carbon emissions and achieve carbon neutrality(known as the"Dual-Carbon"goal)is an inevitable requirement for elevating the environmental resource constraints and realizing harmonious coexis...Striving to peak carbon emissions and achieve carbon neutrality(known as the"Dual-Carbon"goal)is an inevitable requirement for elevating the environmental resource constraints and realizing harmonious coexistence between the mankind and the earth.In the energy system,nuclear energy offers various advantages,such as high energy density,low carbon emission,strong environmental adaptability and large potential for energy co-generation and co-supply.It is one of the supporting energy sources for the transformation and upgradation of the energy system to a clean,efficient and low-carbon way.In this paper,the opportunities and challenges for innovation-driven nuclear energy development in the fields of electricity generation,hydrogen production,heat supply and seawater desalination under the goal of"Dual-Carbon"are discussed and analyzed.Besides,the relevant research on improving the safety and economy of the pressurized water reactor(PWR)and sodium-cooled fast reactor(SFR)conducted by the Nuclear THermal-hydraulic research Lab(NuTHeL)of Xi’an Jiaotong University is briefly introduced.展开更多
A numerical-model-based approach was recently developed for estimating the changes in both the horizontal and vertical loading conditions induced by an approaching longwall face.In this approach, a systematic procedur...A numerical-model-based approach was recently developed for estimating the changes in both the horizontal and vertical loading conditions induced by an approaching longwall face.In this approach, a systematic procedure is used to estimate the model's inputs.Shearing along the bedding planes is modeled with ubiquitous joint elements and interface elements.Coal is modeled with a newly developed coal mass model.The response of the gob is calibrated with back analysis of subsidence data and the results of previously published laboratory tests on rock fragments.The model results were verified with the subsidence and stress data recently collected from a longwall mine in the eastern United States.展开更多
This paper presents the results of a comprehensive study conducted by CONSOL Energy, Marcellus Shale Coalition, and Pennsylvania Coal Association to evaluate the effects of longwall-induced subsurface deformations on ...This paper presents the results of a comprehensive study conducted by CONSOL Energy, Marcellus Shale Coalition, and Pennsylvania Coal Association to evaluate the effects of longwall-induced subsurface deformations on the mechanical integrity of shale gas wells drilled over a longwall abutment pillar.The primary objective is to demonstrate that a properly constructed gas well in a standard longwall abutment pillar can maintain mechanical integrity during and after mining operations. A study site was selected over a southwestern Pennsylvania coal mine, which extracts 457-m-wide longwall faces under about 183 m of cover. Four test wells and four monitoring wells were drilled and installed over a 38-m by84-m centers abutment pillar. In addition to the test wells and monitoring wells, surface subsidence measurements and underground coal pillar pressure measurements were conducted as the 457-m-wide longwall panels on the south and north sides of the abutment pillar were mined by. To evaluate the resulting coal protection casing profile and lateral displacement, three separate 60-arm caliper surveys were conducted. This research represents a very important step and initiative to utilize the knowledge and science obtained from mining research to improve miner and public safety as well as the safety and health of the oil and gas industries.展开更多
This paper presents the results of a 2017 study conducted by the National Institute for Occupational Safety and Health(NIOSH), Pittsburgh Mining Research Division(PMRD), to evaluate the effects of longwall-induced sub...This paper presents the results of a 2017 study conducted by the National Institute for Occupational Safety and Health(NIOSH), Pittsburgh Mining Research Division(PMRD), to evaluate the effects of longwall-induced subsurface deformations within a longwall abutment pillar under deep cover. The 2017 study was conducted in a southwestern Pennsylvania coal mine, which extracts 457 m-wide longwall panels under 361 m of cover. One 198 m-deep, in-place inclinometer monitoring well was drilled and installed over a 45 m by 84 m center abutment pillar. In addition to the monitoring well, surface subsidence measurements and underground coal pillar pressure measurements were conducted as the 457 m-wide longwall panel on the south side of the abutment pillar was being mined. Prior to the first longwall excavation, a number of simulations using FLAC3D^(TM) were conducted to estimate surface subsidence, increases in underground coal pillar pressure, and subsurface horizontal displacements in the monitoring well. Comparisons of the pre-mining FLAC3D simulation results and the surface, subsurface,and underground instrumentation results show that the measured in-place inclinometer casing deformations are in reasonable agreement with those predicted by the 3D finite difference models. The measured surface subsidence and pillar pressure are in excellent agreement with those predicted by the 3D models.Results from this 2017 research clearly indicate that, under deep cover, the measured horizontal displacements within the abutment pillar are approximately one order of magnitude smaller than those measured in a 2014 study under medium cover.展开更多
A finite volume(FV)method for simulating 3D Fluid-Structure Interaction(FSI)is presented in this paper.The fluid flow is simulated using a parallel unstructured multigrid preconditioned implicit compressible solver,wh...A finite volume(FV)method for simulating 3D Fluid-Structure Interaction(FSI)is presented in this paper.The fluid flow is simulated using a parallel unstructured multigrid preconditioned implicit compressible solver,whist a 3D matrix-free implicit unstructured multigrid finite volume solver is employed for the structural dynamics.The two modules are then coupled using a so-called immersed membrane method(IMM).Large-Eddy Simulation(LES)is employed to predict turbulence.Results from several moving boundary and FSI problems are presented to validate proposed methods and demonstrate their efficiency。展开更多
Aims Foliar herbivory and water stress may affect floral traits attractive to pollinators.Plant genotypes may differ in their responses to the interplay between these factors,and evolution of phenotypic plasticity cou...Aims Foliar herbivory and water stress may affect floral traits attractive to pollinators.Plant genotypes may differ in their responses to the interplay between these factors,and evolution of phenotypic plasticity could be expected,particularly in heterogeneous environments.We aimed at evaluating the effects of simulated herbivory and experimental drought on floral traits attractive to pollinators in genetic families of the annual tarweed Madia sativa,which inhabits heterogeneous environments in terms of water availability,herbivore abundance and pollinator abundance.Methods In a greenhouse experiment with 15 inbred lines from a M.sativa population located in central Chile(Mediterranean-type climate),we measured the effects of apical bud damage and reduced water availability on:number of ray florets per flower head,length of ray florets,flower head diameter,number of open flower heads per plant,flowering plant height and flowering time.Important Findings Apical damage and water shortage reduced phenotypic expression of floral traits attractive to pollinators via additive and non-additive effects.Plants in low water showed decreased height and had fewer and shorter ray florets,and fewer and smaller flower heads.Damaged plants showed delayed flowering,were less tall,and showed shorter ray florets and smaller flower heads.The number of ray florets was reduced by damage only in the low water treatment.Plant height,flowering time and number of flower heads showed among-family variation.These traits also showed genetic variation for plasticity to water availability.Ray floret length,flower head size and time to flowering showed genetic variation for plastic responses to apical damage.Plasticity in flowering time may allow M.sativa to adjust to the increased aridity foreseen for its habitat.Because genetic variation for plastic responses was detected,conditions are given for evolutionary responses to selective forces acting on plastic traits.We suggest that the evolution of adaptive floral plasticity in M.sativa in this展开更多
Current structural analysis software programs offer few if any applicable device-specifi c hysteresis rules or nonlinear elements to simulate the precise mechanical behavior of a multiple friction pendulum system(MFPS...Current structural analysis software programs offer few if any applicable device-specifi c hysteresis rules or nonlinear elements to simulate the precise mechanical behavior of a multiple friction pendulum system(MFPS) with numerous sliding interfaces.Based on the concept of subsystems,an equivalent series system that adopts existing nonlinear elements with parameters systematically calculated and mathematically proven through rigorous derivations is proposed.The aim is to simulate the characteristics of sliding motions for an MFPS isolation system with numerous concave sliding interfaces without prior knowledge of detailed information on the mobilized forces at various sliding stages.An MFPS with numerous concave sliding interfaces and one articulated or rigid slider located between these interfaces is divided into two subsystems: the fi rst represents the concave sliding interfaces above the slider,and the second represents those below the slider.The equivalent series system for the entire system is then obtained by connecting those for each subsystem in series.The equivalent series system is validated by comparing numerical results for an MFPS with four sliding interfaces obtained from the proposed method with those from a previous study by Fenz and Constantinou.Furthermore,these numerical results demonstrate that an MFPS isolator with numerous concave sliding interfaces,which may have any number of sliding interfaces,is a good isolation device to protect structures from earthquake damage through appropriate designs with controllable mechanisms.展开更多
A new multifunction thermo-mechanical simulator was successfully developed. The accuracy of measurement and control is very high through all digital control. More than twenty tests may be fulfilled including tension, ...A new multifunction thermo-mechanical simulator was successfully developed. The accuracy of measurement and control is very high through all digital control. More than twenty tests may be fulfilled including tension, compression, torsion, combination large deformation that meets the study of supersteel, etc. Its performance is introduced in the paper, such as designed ideas, machine structure, man-machine interface, control system, etc.展开更多
This study examines the roles of soil-structure interaction （SSI）, higher modes, and damping in a base-isolated structure built on multiple layers of soil overlying a half space. Closed-form solutions for the entire...This study examines the roles of soil-structure interaction （SSI）, higher modes, and damping in a base-isolated structure built on multiple layers of soil overlying a half space. Closed-form solutions for the entire system, including a superstructure, seismic isolator, and numerous soil layers overlying a half-space, were obtained. The formulations obtained in this study simply in terms of well-known frequencies and mechanical impedance ratios can explicitly interpret the dynamic behavior of a base-isolated structure interacting with multiple soil layers overlying a half-space. The key factors influencing the performance of the isolation system are the damping ratio of the isolator and the ratio of the natural frequency of the fixed-base structure to that of the isolated structure by assuming that the superstructure moves as a rigid body. This study reveals that higher damping in the base isolator is unfavorable to higher mode responses that usually dominate the responses of the superstructure and that the damping mechanism plays an important role in transmitting energy in addition to absorbing energy. It is also concluded that it is possible to design a soft soil layer as an isolation system for isolating vibration energy.展开更多
文摘A recent seismic event was recorded by a deep longwall mine in Virginia at 3.7 ML on the local magnitude scale and 3.4 MMS by the United States Geological Survey(USGS) in 2016.Further investigations by the National Institute for Occupational Safety and Health(NIOSH) and Coronado Coal researchers have shown that this event was associated with geological features that have also been associated with other, similar seismic events in Virginia.Detailed mapping and geological exploration in the mining area has made it possible to forecast possible locations for future seismic activity.In order to use the geology as a forecaster of mining-induced seismic events and their energy potential, two primary components are needed.The first component is a long history of recorded seismic events with accurately plotted locations.The second component is a high density of geologic data within the mining area.In this case, 181 events of 1.0 MLor greater were recorded by the mine's seismic network between January, 2009, and October, 2016.Within the mining area, 897 geophysical logs, 224 core holes, and 1031 fiberscope holes were examined by mine geologists.From this information, it was found that overburden thickness, sandstone thickness, and sandstone quality contributed greatly to seismic locations.After the data was analyzed, a pattern became apparent indicating that the majority of seismic events occurred under specific conditions.Three forecast maps were created based on geology of previous seismic locations.The forecast maps have shown an accuracy of within 74%–89% when compared to the recorded 181 events that were1.0 MLor greater when considering three major geological criteria of overburden thickness of 579.12 m or greater, 6.096–12.192 m of sandstone within 15.24 m of the Pocahontas number 3 seam, and a longwall caving height of 4.572 m or less.
基金This work was supported by the AMA Foundation Seed Grant,NIH/NCI1R01CA178445,and NIH/NCI1R01CA217207。
文摘In order to assess Stathmin as an immunohistochemical(IHC)indicator of phosphatidylinositol 3-kinase(PI3K)pathway activity in HPV-negative head&neck squamous cell carcinoma(HNSCC),we compared Stathmin IHC to expression of other pathway components.We also evaluated the relationship between Stathmin IHC and the mutational status of four key pathway genes.Finally,we ascertained whether Stathmin IHC correlates with tumor grade or primary site.Correlation exists between high Stathmin expression and high pAKT1 expression,indicating a role for Stathmin IHC as a marker of pathway activity.Our analysis did not show correlation between Stathmin IHC and mutation of the four genes evaluated.We also observed an association between high Stathmin expression and oropharyngeal primary site.Our results suggest utility of Stathmin IHC as an indicator of PI3K pathway activity,and thereby demonstrate potential relevance of Stathmin IHC in the context,of HNSCC.
基金supported by National High Technical Research and Development Programme of China(No.2002AA331112)supported by the Doctorate Foundation of Northwestern Polytechnical University.
文摘A developmental research has been carried out to deal with the high performance of Cu-Cr-Zr-Mg lead frame alloy by artificial neural network (ANN). Using the cold working to assist in the aging hardening can improve the the hardness and electrical conductivity properties of Cu-Cr-Zr-Mg lead frame alloy. This paper studies the effect of different extent of cold working on the aging properties by a supervised ANN to model the non-linear relationship between processing parameters and the properties. The back-propagation (BP) training algorithm is improved by Levenberg-Marquardt algorithm. A basic repository on the domain knowledge of cold worked aging processes is established via sufficient data mining by the network. The predicted values of the ANN coincide well with the tested data. So an important foundation has been laid for prediction and optimum controlling the rolling and aging properties of Cu-Cr-Zr-Mg alloy.
文摘This paper presents the results of a unique study conducted by the National Institute for Occupational Safety and Health(NIOSH)from 2016 to 2019 to evaluate the effects of longwall-induced subsurface deformations on shale gas well casing integrity and underground miner safety and health.At both deep-cover and shallow-cover instrumentation sites,surface subsidence measurements,subsurface inplace inclinometer measurements,and underground pillar pressure measurements were conducted as longwall panels were mined.Comparisons of the deep-cover and shallow-cover test site results with those from a similar study under medium cover reveal an interesting longwall-induced response scenario.Under shallow and medium covers,measured horizontal displacements within the abutment pillar are one order of magnitude higher than those measured under deep cover.On the other hand,measured vertical compressions under deep cover are one order of magnitude higher than those under shallow and medium covers.However,FLAC3 Dsimulations of the casings indicate that,in all three cases,the P-110 production casings remain intact under longwall-induced deformations and compressions,which has serious implications for future mine design in areas where shale gas wells have been drilled ahead of mining.
文摘Striving to peak carbon emissions and achieve carbon neutrality(known as the"Dual-Carbon"goal)is an inevitable requirement for elevating the environmental resource constraints and realizing harmonious coexistence between the mankind and the earth.In the energy system,nuclear energy offers various advantages,such as high energy density,low carbon emission,strong environmental adaptability and large potential for energy co-generation and co-supply.It is one of the supporting energy sources for the transformation and upgradation of the energy system to a clean,efficient and low-carbon way.In this paper,the opportunities and challenges for innovation-driven nuclear energy development in the fields of electricity generation,hydrogen production,heat supply and seawater desalination under the goal of"Dual-Carbon"are discussed and analyzed.Besides,the relevant research on improving the safety and economy of the pressurized water reactor(PWR)and sodium-cooled fast reactor(SFR)conducted by the Nuclear THermal-hydraulic research Lab(NuTHeL)of Xi’an Jiaotong University is briefly introduced.
文摘A numerical-model-based approach was recently developed for estimating the changes in both the horizontal and vertical loading conditions induced by an approaching longwall face.In this approach, a systematic procedure is used to estimate the model's inputs.Shearing along the bedding planes is modeled with ubiquitous joint elements and interface elements.Coal is modeled with a newly developed coal mass model.The response of the gob is calibrated with back analysis of subsidence data and the results of previously published laboratory tests on rock fragments.The model results were verified with the subsidence and stress data recently collected from a longwall mine in the eastern United States.
文摘This paper presents the results of a comprehensive study conducted by CONSOL Energy, Marcellus Shale Coalition, and Pennsylvania Coal Association to evaluate the effects of longwall-induced subsurface deformations on the mechanical integrity of shale gas wells drilled over a longwall abutment pillar.The primary objective is to demonstrate that a properly constructed gas well in a standard longwall abutment pillar can maintain mechanical integrity during and after mining operations. A study site was selected over a southwestern Pennsylvania coal mine, which extracts 457-m-wide longwall faces under about 183 m of cover. Four test wells and four monitoring wells were drilled and installed over a 38-m by84-m centers abutment pillar. In addition to the test wells and monitoring wells, surface subsidence measurements and underground coal pillar pressure measurements were conducted as the 457-m-wide longwall panels on the south and north sides of the abutment pillar were mined by. To evaluate the resulting coal protection casing profile and lateral displacement, three separate 60-arm caliper surveys were conducted. This research represents a very important step and initiative to utilize the knowledge and science obtained from mining research to improve miner and public safety as well as the safety and health of the oil and gas industries.
文摘This paper presents the results of a 2017 study conducted by the National Institute for Occupational Safety and Health(NIOSH), Pittsburgh Mining Research Division(PMRD), to evaluate the effects of longwall-induced subsurface deformations within a longwall abutment pillar under deep cover. The 2017 study was conducted in a southwestern Pennsylvania coal mine, which extracts 457 m-wide longwall panels under 361 m of cover. One 198 m-deep, in-place inclinometer monitoring well was drilled and installed over a 45 m by 84 m center abutment pillar. In addition to the monitoring well, surface subsidence measurements and underground coal pillar pressure measurements were conducted as the 457 m-wide longwall panel on the south side of the abutment pillar was being mined. Prior to the first longwall excavation, a number of simulations using FLAC3D^(TM) were conducted to estimate surface subsidence, increases in underground coal pillar pressure, and subsurface horizontal displacements in the monitoring well. Comparisons of the pre-mining FLAC3D simulation results and the surface, subsurface,and underground instrumentation results show that the measured in-place inclinometer casing deformations are in reasonable agreement with those predicted by the 3D finite difference models. The measured surface subsidence and pillar pressure are in excellent agreement with those predicted by the 3D models.Results from this 2017 research clearly indicate that, under deep cover, the measured horizontal displacements within the abutment pillar are approximately one order of magnitude smaller than those measured in a 2014 study under medium cover.
文摘A finite volume(FV)method for simulating 3D Fluid-Structure Interaction(FSI)is presented in this paper.The fluid flow is simulated using a parallel unstructured multigrid preconditioned implicit compressible solver,whist a 3D matrix-free implicit unstructured multigrid finite volume solver is employed for the structural dynamics.The two modules are then coupled using a so-called immersed membrane method(IMM).Large-Eddy Simulation(LES)is employed to predict turbulence.Results from several moving boundary and FSI problems are presented to validate proposed methods and demonstrate their efficiency。
基金Fondo de Desarrollo Científico y Tecnológico(Chile)(3040036 to W.G.L.).
文摘Aims Foliar herbivory and water stress may affect floral traits attractive to pollinators.Plant genotypes may differ in their responses to the interplay between these factors,and evolution of phenotypic plasticity could be expected,particularly in heterogeneous environments.We aimed at evaluating the effects of simulated herbivory and experimental drought on floral traits attractive to pollinators in genetic families of the annual tarweed Madia sativa,which inhabits heterogeneous environments in terms of water availability,herbivore abundance and pollinator abundance.Methods In a greenhouse experiment with 15 inbred lines from a M.sativa population located in central Chile(Mediterranean-type climate),we measured the effects of apical bud damage and reduced water availability on:number of ray florets per flower head,length of ray florets,flower head diameter,number of open flower heads per plant,flowering plant height and flowering time.Important Findings Apical damage and water shortage reduced phenotypic expression of floral traits attractive to pollinators via additive and non-additive effects.Plants in low water showed decreased height and had fewer and shorter ray florets,and fewer and smaller flower heads.Damaged plants showed delayed flowering,were less tall,and showed shorter ray florets and smaller flower heads.The number of ray florets was reduced by damage only in the low water treatment.Plant height,flowering time and number of flower heads showed among-family variation.These traits also showed genetic variation for plasticity to water availability.Ray floret length,flower head size and time to flowering showed genetic variation for plastic responses to apical damage.Plasticity in flowering time may allow M.sativa to adjust to the increased aridity foreseen for its habitat.Because genetic variation for plastic responses was detected,conditions are given for evolutionary responses to selective forces acting on plastic traits.We suggest that the evolution of adaptive floral plasticity in M.sativa in this
文摘Current structural analysis software programs offer few if any applicable device-specifi c hysteresis rules or nonlinear elements to simulate the precise mechanical behavior of a multiple friction pendulum system(MFPS) with numerous sliding interfaces.Based on the concept of subsystems,an equivalent series system that adopts existing nonlinear elements with parameters systematically calculated and mathematically proven through rigorous derivations is proposed.The aim is to simulate the characteristics of sliding motions for an MFPS isolation system with numerous concave sliding interfaces without prior knowledge of detailed information on the mobilized forces at various sliding stages.An MFPS with numerous concave sliding interfaces and one articulated or rigid slider located between these interfaces is divided into two subsystems: the fi rst represents the concave sliding interfaces above the slider,and the second represents those below the slider.The equivalent series system for the entire system is then obtained by connecting those for each subsystem in series.The equivalent series system is validated by comparing numerical results for an MFPS with four sliding interfaces obtained from the proposed method with those from a previous study by Fenz and Constantinou.Furthermore,these numerical results demonstrate that an MFPS isolator with numerous concave sliding interfaces,which may have any number of sliding interfaces,is a good isolation device to protect structures from earthquake damage through appropriate designs with controllable mechanisms.
基金supported by the National Natural Science Foundation of China(No.50227401)
文摘A new multifunction thermo-mechanical simulator was successfully developed. The accuracy of measurement and control is very high through all digital control. More than twenty tests may be fulfilled including tension, compression, torsion, combination large deformation that meets the study of supersteel, etc. Its performance is introduced in the paper, such as designed ideas, machine structure, man-machine interface, control system, etc.
文摘This study examines the roles of soil-structure interaction （SSI）, higher modes, and damping in a base-isolated structure built on multiple layers of soil overlying a half space. Closed-form solutions for the entire system, including a superstructure, seismic isolator, and numerous soil layers overlying a half-space, were obtained. The formulations obtained in this study simply in terms of well-known frequencies and mechanical impedance ratios can explicitly interpret the dynamic behavior of a base-isolated structure interacting with multiple soil layers overlying a half-space. The key factors influencing the performance of the isolation system are the damping ratio of the isolator and the ratio of the natural frequency of the fixed-base structure to that of the isolated structure by assuming that the superstructure moves as a rigid body. This study reveals that higher damping in the base isolator is unfavorable to higher mode responses that usually dominate the responses of the superstructure and that the damping mechanism plays an important role in transmitting energy in addition to absorbing energy. It is also concluded that it is possible to design a soft soil layer as an isolation system for isolating vibration energy.
