The non-axisymmetrical vibration of elastic circular plate resting on a layered transversely isotropic saturated ground was studied. First, the 3-d dynamic equations in cylindrical coordinate for transversely isotropi...The non-axisymmetrical vibration of elastic circular plate resting on a layered transversely isotropic saturated ground was studied. First, the 3-d dynamic equations in cylindrical coordinate for transversely isotropic saturated soils were transformed into a group of governing differential equations with 1-order by the technique of Fourier expanding with respect to azimuth, and the state equation is established by Hankel integral transform method, furthermore the transfer matrixes within layered media are derived based on the solutions of the state equation. Secondly, by the transfer matrixes, the general solutions of dynamic response for layered transversely isotropic saturated ground excited by an arbitrary harmonic force were established under the boundary conditions, drainage conditions on the surface of ground as well as the contact conditions. Thirdly, the problem was led to a pair of dual integral equations describing the mixed boundaryvalue problem which can be reduced to the Fredholm integral equations of the second kind solved by numerical procedure easily. At the end of this paper, a numerical result concerning vertical and radical displacements both the surface of saturated ground and plate is evaluated.展开更多
Discrete models such as the lumped parameter model and the finite element model are widely used in the solution of soil amplification of earthquakes. However, neither of the models will accurately estimate the natural...Discrete models such as the lumped parameter model and the finite element model are widely used in the solution of soil amplification of earthquakes. However, neither of the models will accurately estimate the natural frequencies of soil deposit, nor simulate a damping of frequency independence. This research develops a new discrete model for onedimensional viscoelastic response analysis of layered soil deposit based on the mode equivalence method. The new discrete model is a one-dimensional equivalent multi-degree-of-freedom（MDOF） system characterized by a series of concentrated masses, springs and dashpots with a special configuration. The dynamic response of the equivalent MDOF system is analytically derived and the physical parameters are formulated in terms of modal properties. The equivalent MDOF system is verified through a comparison of amplification functions with the available theoretical solutions. The appropriate number of degrees of freedom（DOFs） in the equivalent MDOF system is estimated. A comparative study of the equivalent MDOF system with the existing discrete models is performed. It is shown that the proposed equivalent MDOF system can exactly present the natural frequencies and the hysteretic damping of soil deposits and provide more accurate results with fewer DOFs.展开更多
Background:National forest inventories(NFI)have a long history providing data to obtain nationally representative and accurate estimates of growing stock.Today,in most NFIs additional data are collected to provide inf...Background:National forest inventories(NFI)have a long history providing data to obtain nationally representative and accurate estimates of growing stock.Today,in most NFIs additional data are collected to provide information on a range of forest ecosystem functions such as biodiversity,habitat,nutrient and carbon dynamics.An important driver of nutrient and C cycling is decomposing biomass produced by forest vegetation.Several studies have demonstrated that understory vegetation,particularly annual plant litter of the herb layer can contribute significantly to nutrient and C cycling in forests.A methodology to obtain comprehensive,consistent and nationally representative estimates of herb layer biomass on NFI plots could provide added value to NFIs by complementing the existing strong basis of biomass estimates of the tree and tall shrub layer.The study was based on data from the Swiss NFI since it covers a large environmental gradient,which extends its applicability to other NFIs.Results:Based on data from 405 measurements in nine forest strata,a parsimonious model formulation was identified to predict total and non-ligneous herb layer biomass.Besides herb layer cover,elevation was the main statistically significant explanatory variable for biomass.The regression models accurately predicted biomass based on absolute percentage cover(for total biomass:R2=0.65,p=0;for non-ligneous biomass:R2=0.76;p=0)as well as on cover classes(R2=0.83;p=0;and R2=0.79,p=0),which are typically used in NFIs.The good performance was supported by the verification with data from repeated samples.For the 2 nd,3 rd,and 4 th Swiss NFI estimates of non-ligneous above-ground herb layer biomass 586.6±7.7,575.2±7.6,and 586.7±7.9 kg·ha-1,respectively.Conclusions:The study presents a methodology to obtain herb layer biomass estimates based on a harmonized and standardized attribute available in many NFIs.The result of this study was a parsimonious model requiring only elevation data of sample plots in addition to NFI cover estimates to provide unbiased estimates at the national scale.These qualities are particularly important as they ensure accurate,consistent,and comparable results.展开更多
A prototype of a solar ground-layer adaptive optics （GLAO） system, which consists of a multi-direction corre- lating Shack-Hartmann wavefront sensor with 30 effective subapertures and about a 1 arcmin field of view ...A prototype of a solar ground-layer adaptive optics （GLAO） system, which consists of a multi-direction corre- lating Shack-Hartmann wavefront sensor with 30 effective subapertures and about a 1 arcmin field of view （FoV） in each subaperture, a deformable mirror with 151 actuators conjugated to the telescope entrance pupil, and a custom-built real-time controller based on field-programmable gate array and multi-core digital signal processor （DSP）, is implemented at the 1 m New Vacuum Solar Telescope at Fuxian Solar Observatory and saw its first light on January 12th, 2016. The on-sky observational results show that the solar image is apparently improved in the whole FoV over 1 arcmin with the GLAO correction.展开更多
基金Project supported by the National Natural Science Foundation of China(No.50678108)the Natural Science Foundation of Zhejiang Province(No.Y106264 )
文摘The non-axisymmetrical vibration of elastic circular plate resting on a layered transversely isotropic saturated ground was studied. First, the 3-d dynamic equations in cylindrical coordinate for transversely isotropic saturated soils were transformed into a group of governing differential equations with 1-order by the technique of Fourier expanding with respect to azimuth, and the state equation is established by Hankel integral transform method, furthermore the transfer matrixes within layered media are derived based on the solutions of the state equation. Secondly, by the transfer matrixes, the general solutions of dynamic response for layered transversely isotropic saturated ground excited by an arbitrary harmonic force were established under the boundary conditions, drainage conditions on the surface of ground as well as the contact conditions. Thirdly, the problem was led to a pair of dual integral equations describing the mixed boundaryvalue problem which can be reduced to the Fredholm integral equations of the second kind solved by numerical procedure easily. At the end of this paper, a numerical result concerning vertical and radical displacements both the surface of saturated ground and plate is evaluated.
基金National Natural Science Foundation of China(51208296&51478343)Shanghai Committee of Science and Technology(13231200503)+2 种基金Fundamental Research Funds for the Central Universities(2013KJ095&101201438)Shanghai Educational Development Foundation(13CG17)National Key Technology R&D Program(2012BAK24B04)
文摘Discrete models such as the lumped parameter model and the finite element model are widely used in the solution of soil amplification of earthquakes. However, neither of the models will accurately estimate the natural frequencies of soil deposit, nor simulate a damping of frequency independence. This research develops a new discrete model for onedimensional viscoelastic response analysis of layered soil deposit based on the mode equivalence method. The new discrete model is a one-dimensional equivalent multi-degree-of-freedom（MDOF） system characterized by a series of concentrated masses, springs and dashpots with a special configuration. The dynamic response of the equivalent MDOF system is analytically derived and the physical parameters are formulated in terms of modal properties. The equivalent MDOF system is verified through a comparison of amplification functions with the available theoretical solutions. The appropriate number of degrees of freedom（DOFs） in the equivalent MDOF system is estimated. A comparative study of the equivalent MDOF system with the existing discrete models is performed. It is shown that the proposed equivalent MDOF system can exactly present the natural frequencies and the hysteretic damping of soil deposits and provide more accurate results with fewer DOFs.
基金supported financially by the Swiss Federal Office for the Environment(FOEN)(project monitoring by N.Rogiers,contract no.:06.0091.PZ/P043-0606)financial support from FOEN。
文摘Background:National forest inventories(NFI)have a long history providing data to obtain nationally representative and accurate estimates of growing stock.Today,in most NFIs additional data are collected to provide information on a range of forest ecosystem functions such as biodiversity,habitat,nutrient and carbon dynamics.An important driver of nutrient and C cycling is decomposing biomass produced by forest vegetation.Several studies have demonstrated that understory vegetation,particularly annual plant litter of the herb layer can contribute significantly to nutrient and C cycling in forests.A methodology to obtain comprehensive,consistent and nationally representative estimates of herb layer biomass on NFI plots could provide added value to NFIs by complementing the existing strong basis of biomass estimates of the tree and tall shrub layer.The study was based on data from the Swiss NFI since it covers a large environmental gradient,which extends its applicability to other NFIs.Results:Based on data from 405 measurements in nine forest strata,a parsimonious model formulation was identified to predict total and non-ligneous herb layer biomass.Besides herb layer cover,elevation was the main statistically significant explanatory variable for biomass.The regression models accurately predicted biomass based on absolute percentage cover(for total biomass:R2=0.65,p=0;for non-ligneous biomass:R2=0.76;p=0)as well as on cover classes(R2=0.83;p=0;and R2=0.79,p=0),which are typically used in NFIs.The good performance was supported by the verification with data from repeated samples.For the 2 nd,3 rd,and 4 th Swiss NFI estimates of non-ligneous above-ground herb layer biomass 586.6±7.7,575.2±7.6,and 586.7±7.9 kg·ha-1,respectively.Conclusions:The study presents a methodology to obtain herb layer biomass estimates based on a harmonized and standardized attribute available in many NFIs.The result of this study was a parsimonious model requiring only elevation data of sample plots in addition to NFI cover estimates to provide unbiased estimates at the national scale.These qualities are particularly important as they ensure accurate,consistent,and comparable results.
基金supported by the National Natural Science Foundation of China(No.11178004)the Laboratory Innovation Foundation of the Chinese Academy of Sciences(No.YJ15K007)
文摘A prototype of a solar ground-layer adaptive optics （GLAO） system, which consists of a multi-direction corre- lating Shack-Hartmann wavefront sensor with 30 effective subapertures and about a 1 arcmin field of view （FoV） in each subaperture, a deformable mirror with 151 actuators conjugated to the telescope entrance pupil, and a custom-built real-time controller based on field-programmable gate array and multi-core digital signal processor （DSP）, is implemented at the 1 m New Vacuum Solar Telescope at Fuxian Solar Observatory and saw its first light on January 12th, 2016. The on-sky observational results show that the solar image is apparently improved in the whole FoV over 1 arcmin with the GLAO correction.
