An investigation of soil-pile-structure interaction is carried out, based on a large reciprocating compressor installed on an elevated concrete foundation （table top structure）. A practical method is described for t...An investigation of soil-pile-structure interaction is carried out, based on a large reciprocating compressor installed on an elevated concrete foundation （table top structure）. A practical method is described for the dynamic analysis, and compared with a 3D finite element （FE） model. Two commercial software packages are used for dynamic analysis considering the soilpile-structure interaction （SPSI）. Stiffness and damping of the pile foundation are generated from a computer program, and then input into the FE model. To examine the SPSI thoroughly, three cases for the soil, piles and superstructure are considered and compared. In the first case, the interaction is fully taken into account, that is, both the superstructure and soil-pile system are flexible. In the second case, the superstructure is flexible but fixed to a rigid base, with no deformation in the base （no SSI）. In the third case, the dynamic soil-pile interaction is taken into account, but the table top structure is assumed to be rigid. From the comparison beteen the results of these three cases some conclusions are made, which could be helpful for engineering practice.展开更多
Bridges are a part of vital infrastructure,which should operate even after a disaster to keep emergency services running.There have been numerous bridge failures during major past earthquakes due to liquefaction.Among...Bridges are a part of vital infrastructure,which should operate even after a disaster to keep emergency services running.There have been numerous bridge failures during major past earthquakes due to liquefaction.Among other categories of failures,mid span collapse(without the failure of abutments)of pile supported bridges founded in liquefiable deposits are still observed even in most recent earthquakes.This mechanism of collapse is attributed to the effects related to the differential elongation of natural period of the individual piers during liquefaction.A shake table investigation has been carried out in this study to verify mechanisms behind midspan collapse of pile supported bridges in liquefiable deposits.In this investigation,a typical pile supported bridge is scaled down,and its foundations pass through the liquefiable loose sandy soil and rest in a dense gravel layer.White noise motions of increasing acceleration magnitude have been applied to initiate progressive liquefaction and to characterize the dynamic features of the bridge.It has been found that as the liquefaction of the soil sets in,the natural frequency of individual bridge support is reduced,with the highest reduction occurring near the central spans.As a result,there is differential lateral displacement and bending moment demand on the piles.It has also been observed that for the central pile,the maximum bending moment in the pile will occur at a higher elevation,as compared to that of the interface of soils of varied stiffness,unlike the abutment piles.The practical implications of this research are also highlighted.展开更多
厦门大学植物激素研究组从月光花(Calonyction aculeatum L. House)叶中提取出一种活性物质,称为月光花素甲。它对植物具有明显的生理活性,并能促进作物生长,达到增产的效果。方一苇等通过质子核磁共振和电子轰击质谱分析,初步确定月光...厦门大学植物激素研究组从月光花(Calonyction aculeatum L. House)叶中提取出一种活性物质,称为月光花素甲。它对植物具有明显的生理活性,并能促进作物生长,达到增产的效果。方一苇等通过质子核磁共振和电子轰击质谱分析,初步确定月光花素甲是11-羟基一十六烷酸乙酯和6-去氧己醛糖组成的糖甙类物质。展开更多
We report on infrared supercontinuum （SC） generation in step-index fluoroindate-based fiber by using an all-fiber laser source. In comparison to widely used ZBLAN fibers for high-power mid-infrared （MIR） SC genera...We report on infrared supercontinuum （SC） generation in step-index fluoroindate-based fiber by using an all-fiber laser source. In comparison to widely used ZBLAN fibers for high-power mid-infrared （MIR） SC generation, fluoroindate fibers have multiphoton absorption edges at significandy longer wavelengths and can sustain similar intensities. Recent developments highlighted in the present study allowed the production of fluoroindate fibers with MIR background loss of 2 dB/km, which is similar to or even better than ZBLAN fibers. By using an all-fiber picosecond laser source based on an erbium amplifier followed by a thulium power amplifier, we demonstrate the generation of 1.0 W infrared SC spanning over 2.25 octaves from 1 μm to 5 μm. The generated MIR SC also exhibits high spectral flatness with a 6 dB spectral bandwidth from 1.91 μm to 4.77 μm and an average power two orders of magnitude greater than in previous demonstrations with a similar spectral distribution.展开更多
A persistent challenge in molecular modeling of thermoset polymers is capturing the effects of chemical composition and degree of crosslinking(DC)on dynamical and mechanical properties with high computational efficien...A persistent challenge in molecular modeling of thermoset polymers is capturing the effects of chemical composition and degree of crosslinking(DC)on dynamical and mechanical properties with high computational efficiency.We established a coarse-graining(CG)approach combining the energy renormalization method with Gaussian process surrogate models of molecular dynamics simulations.This allows a machine-learning informed functional calibration of DC-dependent CG force field parameters.Taking versatile epoxy resins consisting of Bisphenol A diglycidyl ether combined with curing agent of either 4,4-Diaminodicyclohexylmethane or polyoxypropylene diamines,we demonstrated excellent agreement between all-atom and CG predictions for density,Debye-Waller factor,Young’s modulus,and yield stress at any DC.We further introduced a surrogate model-enabled simplification of the functional forms of 14 nonbonded calibration parameters by quantifying the uncertainty of a candidate set of calibration functions.The framework established provides an efficient methodology for chemistry-specific,large-scale investigations of the dynamics and mechanics of epoxy resins.展开更多
Purpose The constant work-rate to exhaustion tests must be repeated several times at each work-rate to estimate subject-level trial-to-trial variance(intra-individual variability,IIV)of critical power(CP)and work capa...Purpose The constant work-rate to exhaustion tests must be repeated several times at each work-rate to estimate subject-level trial-to-trial variance(intra-individual variability,IIV)of critical power(CP)and work capacity(W').Alternatively,these parameters and their variance can be estimated by repeating the 3-min all-out test(3MT)fewer times.The purpose of this study was to propose a method to determine subject-level repeatability of the 3MT and demonstrate the need to repeat the test multiple times to estimate IIV.Methods Seven cyclists performed a ramp test and four 3MTs on a CompuTrainer.The parameters CP,W',peak power(Pp),and total work(TW)were compared across trials using repeated measures ANOVA,Bland-Altman analysis,Intraclass Cor-relation Coefficients(ICC),Typical Error(TE)of measurement,and Coefficient of Variation(CV).Results For the group,average CP and W'were 284±58 W and 10.214±3.143 kJ.The reliability statistics,CP(ICC=0.97,TE=8 W,CV=2.94%)and W'(ICC=0.88,TE=1.11 kJ,CV=10.87%),indicated strong agreement.Subject-level repeatability was determined by comparing time-to-peak power(TPp),absolute difference in Pp(δPp),and TW(δTW)for pairs of 3MTs.The average IIVs estimated by the 95%confidence intervals were±15 W for CP and±1.68 kJ for W'.Conclusions Thresholds are proposed for TPp(7 s),δPp(10%),andδTW(3%)to determine subject-level repeatability of the 3MT before computing the IIV of CP and W'.It is suggested that the 3MT is repeated at least three times to estimate the IIV,which aids in personalized measurement of training improvements and performance optimization。展开更多
文摘An investigation of soil-pile-structure interaction is carried out, based on a large reciprocating compressor installed on an elevated concrete foundation （table top structure）. A practical method is described for the dynamic analysis, and compared with a 3D finite element （FE） model. Two commercial software packages are used for dynamic analysis considering the soilpile-structure interaction （SPSI）. Stiffness and damping of the pile foundation are generated from a computer program, and then input into the FE model. To examine the SPSI thoroughly, three cases for the soil, piles and superstructure are considered and compared. In the first case, the interaction is fully taken into account, that is, both the superstructure and soil-pile system are flexible. In the second case, the superstructure is flexible but fixed to a rigid base, with no deformation in the base （no SSI）. In the third case, the dynamic soil-pile interaction is taken into account, but the table top structure is assumed to be rigid. From the comparison beteen the results of these three cases some conclusions are made, which could be helpful for engineering practice.
文摘Bridges are a part of vital infrastructure,which should operate even after a disaster to keep emergency services running.There have been numerous bridge failures during major past earthquakes due to liquefaction.Among other categories of failures,mid span collapse(without the failure of abutments)of pile supported bridges founded in liquefiable deposits are still observed even in most recent earthquakes.This mechanism of collapse is attributed to the effects related to the differential elongation of natural period of the individual piers during liquefaction.A shake table investigation has been carried out in this study to verify mechanisms behind midspan collapse of pile supported bridges in liquefiable deposits.In this investigation,a typical pile supported bridge is scaled down,and its foundations pass through the liquefiable loose sandy soil and rest in a dense gravel layer.White noise motions of increasing acceleration magnitude have been applied to initiate progressive liquefaction and to characterize the dynamic features of the bridge.It has been found that as the liquefaction of the soil sets in,the natural frequency of individual bridge support is reduced,with the highest reduction occurring near the central spans.As a result,there is differential lateral displacement and bending moment demand on the piles.It has also been observed that for the central pile,the maximum bending moment in the pile will occur at a higher elevation,as compared to that of the interface of soils of varied stiffness,unlike the abutment piles.The practical implications of this research are also highlighted.
文摘厦门大学植物激素研究组从月光花(Calonyction aculeatum L. House)叶中提取出一种活性物质,称为月光花素甲。它对植物具有明显的生理活性,并能促进作物生长,达到增产的效果。方一苇等通过质子核磁共振和电子轰击质谱分析,初步确定月光花素甲是11-羟基一十六烷酸乙酯和6-去氧己醛糖组成的糖甙类物质。
文摘We report on infrared supercontinuum （SC） generation in step-index fluoroindate-based fiber by using an all-fiber laser source. In comparison to widely used ZBLAN fibers for high-power mid-infrared （MIR） SC generation, fluoroindate fibers have multiphoton absorption edges at significandy longer wavelengths and can sustain similar intensities. Recent developments highlighted in the present study allowed the production of fluoroindate fibers with MIR background loss of 2 dB/km, which is similar to or even better than ZBLAN fibers. By using an all-fiber picosecond laser source based on an erbium amplifier followed by a thulium power amplifier, we demonstrate the generation of 1.0 W infrared SC spanning over 2.25 octaves from 1 μm to 5 μm. The generated MIR SC also exhibits high spectral flatness with a 6 dB spectral bandwidth from 1.91 μm to 4.77 μm and an average power two orders of magnitude greater than in previous demonstrations with a similar spectral distribution.
基金This work is supported by the Center for Hierarchical Materials Design(CHiMaD)that is funded by the National Institute of Standards and Technology(NIST)(award#70NANB19H005)as well as from the Departments of Civil and Mechanical Engineering at Northwestern University and a supercomputing grant from Northwestern University High Performance Computing Center and the Department of Defense Supercomputing Resource Center.Z.M.acknowledge startup funds from Clemson University,SC TRIMH support(P20 GM121342)support by the NSF and SC EPSCoR Program(NSF Award#OIA-1655740 and SC EPSCoR Grant#21-SA05).
文摘A persistent challenge in molecular modeling of thermoset polymers is capturing the effects of chemical composition and degree of crosslinking(DC)on dynamical and mechanical properties with high computational efficiency.We established a coarse-graining(CG)approach combining the energy renormalization method with Gaussian process surrogate models of molecular dynamics simulations.This allows a machine-learning informed functional calibration of DC-dependent CG force field parameters.Taking versatile epoxy resins consisting of Bisphenol A diglycidyl ether combined with curing agent of either 4,4-Diaminodicyclohexylmethane or polyoxypropylene diamines,we demonstrated excellent agreement between all-atom and CG predictions for density,Debye-Waller factor,Young’s modulus,and yield stress at any DC.We further introduced a surrogate model-enabled simplification of the functional forms of 14 nonbonded calibration parameters by quantifying the uncertainty of a candidate set of calibration functions.The framework established provides an efficient methodology for chemistry-specific,large-scale investigations of the dynamics and mechanics of epoxy resins.
文摘Purpose The constant work-rate to exhaustion tests must be repeated several times at each work-rate to estimate subject-level trial-to-trial variance(intra-individual variability,IIV)of critical power(CP)and work capacity(W').Alternatively,these parameters and their variance can be estimated by repeating the 3-min all-out test(3MT)fewer times.The purpose of this study was to propose a method to determine subject-level repeatability of the 3MT and demonstrate the need to repeat the test multiple times to estimate IIV.Methods Seven cyclists performed a ramp test and four 3MTs on a CompuTrainer.The parameters CP,W',peak power(Pp),and total work(TW)were compared across trials using repeated measures ANOVA,Bland-Altman analysis,Intraclass Cor-relation Coefficients(ICC),Typical Error(TE)of measurement,and Coefficient of Variation(CV).Results For the group,average CP and W'were 284±58 W and 10.214±3.143 kJ.The reliability statistics,CP(ICC=0.97,TE=8 W,CV=2.94%)and W'(ICC=0.88,TE=1.11 kJ,CV=10.87%),indicated strong agreement.Subject-level repeatability was determined by comparing time-to-peak power(TPp),absolute difference in Pp(δPp),and TW(δTW)for pairs of 3MTs.The average IIVs estimated by the 95%confidence intervals were±15 W for CP and±1.68 kJ for W'.Conclusions Thresholds are proposed for TPp(7 s),δPp(10%),andδTW(3%)to determine subject-level repeatability of the 3MT before computing the IIV of CP and W'.It is suggested that the 3MT is repeated at least three times to estimate the IIV,which aids in personalized measurement of training improvements and performance optimization。
