Plants respond to drought stress with different physical manners, such as morphology and color of leaves. Thus, plants can be considered as a sort of living-sensors for monitoring dynamic of soil water content or the ...Plants respond to drought stress with different physical manners, such as morphology and color of leaves. Thus, plants can be considered as a sort of living-sensors for monitoring dynamic of soil water content or the stored water in plant body. Because of difficulty to identify the early wilting symptom of plants from the results in 2D （two-dimension） space, this paper presented a preliminary study with 3D （three-dimension）-based image, in which a laser scanner was used for achieving the morphological information of zucchini （Cucurbita pepo） leaves. Moreover, a leaf wilting index （DLWIF） was defined by fractal dimension. The experiment consisted of phase-1 for observing the temporal variation of DLWIF and phase-2 for the validation of this index. During the experiment, air temperature, luminous intensity, and volumetric soil water contents （VSWC） were simultaneously recorded over time. The results of both phases fitted the bisector （line： 1：1） with R2=0.903 and REMS=0.155. More significantly, the influence of VSWC with three levels （0.22, 0.30, and 0.36 cm3 cm-3） on the response of plant samples to drought stress was observed from separated traces of DLWIF. In brief, two conclusions have been made： （i） the laser scanner is an effective tool for the non-contact detection of morphological wilting of plants, and （ii） defined DLWIF can be a promising indicator for a category of plants like zucchini.展开更多
In this paper, the evaluation of stress intensity factor of plane crack problems for orthotropic plate of equal-parameter is investigated using a fractal two-level finite element method （F2LFEM）. The general solutio...In this paper, the evaluation of stress intensity factor of plane crack problems for orthotropic plate of equal-parameter is investigated using a fractal two-level finite element method （F2LFEM）. The general solution of an orthotropic crack problem is obtained by assimilating the problem with isotropic crack problem, and is employed as the global interpolation function in F2LFEM. In the neighborhood of crack tip of the crack plate, the fractal geometry concept is introduced to achieve the similar meshes having similarity ratio less than one and generate an infinitesimal mesh so that the relationship between the stiffness matrices of two adjacent layers is equal. A large number of degrees of freedom around the crack tip are transformed to a small set of generalized coordinates. Numerical examples show that this method is efficient and accurate in evaluating the stress intensity factor （SIF）.展开更多
This study investigates the viscoelastic behavior of soft bio-fibres in association with their fractal structures. A spring-dashpot fractal network with the self-similar topology, named the -type fractal ladder hyper-...This study investigates the viscoelastic behavior of soft bio-fibres in association with their fractal structures. A spring-dashpot fractal network with the self-similar topology, named the -type fractal ladder hyper-cell (FLHC), is abstracted from the micro/nano-structure of ligaments and tendons (LTs). Its constitutive operator is derived by the Heaviside operational calculus, which is of intrinsic fractional order. In terms of this operator, the long-term viscoelastic relaxation of bio-fibres arising from the fractal ladder topology is expounded. In addition, the fractional-order viscoelastic constitutive equation is obtained based on the FLHC of LTs, and its results are consistent with those of available human knee and spinal LT relaxation experiments. Results on the constitutive equation of FLHCs are formulated into two propositions. The multidisciplinary invariance and implications from the fractal ladder pattern of bio-fibres are also discussed.展开更多
The theory of the fractal structure characterizing propagation of a crack through identification of its generator is presented. It’s generating fractal, the peculiarities of its construction and the way to measure it...The theory of the fractal structure characterizing propagation of a crack through identification of its generator is presented. It’s generating fractal, the peculiarities of its construction and the way to measure its segments are defined, and a theorem on the inverse scale property of such and other of the axial symmetry property of the fractal generator are presented and demonstrated. The theory is applied on 6061-T6 aluminum samples, using SENB probes. Direction of crack propagation and its fractal dimension are calculated numerically. Results obtained from modeling the direction of crack propagation through mechanics of elastic linear fracture and the one proposed here, called geometrical fractal fracture, are compared, thus developing the mirror case.展开更多
The purpose of this study is 1) to present a biomechanical model for evaluating the myogenic power expended in an arterial segment due to vascular smooth muscle contraction (VSMC) and 2) to assess the total power expe...The purpose of this study is 1) to present a biomechanical model for evaluating the myogenic power expended in an arterial segment due to vascular smooth muscle contraction (VSMC) and 2) to assess the total power expenditure in the entire systemic arterial tree by utilizing the fractal nature of the branching architecture. The model is based on the mechanical equilibrium between the stretch stress exerted by blood pressure inside the vessel lumen and constricting stress elicited by VSMC in the vascular wall. An expression for myogenic power expenditure is formulated for a unit wall mass as a function of the internal vessel radius and extent of strain. This expression was then integrated over selected range of vessel radii, by taking into account of the fractal nature of the branching structure. When the total myogenic power expended in the systemic arterial tree in rat at the moderate strain level is converted to the oxygen consumption rate, it amounts to approximately 18% of the whole body oxygen consumption rate. This suggests that the mechanical power expenditure due to VSMC is a significant factor that should not be ignored in studies of vascular energetics.展开更多
基金the Chinese-German Center for Scientific Promotion (Chinesisch-Deutsches Zentrum für Wissenschaftsfrderung) under the Project of Sino-German Research Group (GZ494)the Beijing Municipal Education Commission for Building Scientific Research and Scientific Research Base (2008BJKY01)+1 种基金the German Academic Exchange Service (DAAD),and China Scholarship Council (CSC) for enhancing our cooperationthe International Cooperation Fund of Ministry of Science and Technology, China (2010DFA34670)
文摘Plants respond to drought stress with different physical manners, such as morphology and color of leaves. Thus, plants can be considered as a sort of living-sensors for monitoring dynamic of soil water content or the stored water in plant body. Because of difficulty to identify the early wilting symptom of plants from the results in 2D （two-dimension） space, this paper presented a preliminary study with 3D （three-dimension）-based image, in which a laser scanner was used for achieving the morphological information of zucchini （Cucurbita pepo） leaves. Moreover, a leaf wilting index （DLWIF） was defined by fractal dimension. The experiment consisted of phase-1 for observing the temporal variation of DLWIF and phase-2 for the validation of this index. During the experiment, air temperature, luminous intensity, and volumetric soil water contents （VSWC） were simultaneously recorded over time. The results of both phases fitted the bisector （line： 1：1） with R2=0.903 and REMS=0.155. More significantly, the influence of VSWC with three levels （0.22, 0.30, and 0.36 cm3 cm-3） on the response of plant samples to drought stress was observed from separated traces of DLWIF. In brief, two conclusions have been made： （i） the laser scanner is an effective tool for the non-contact detection of morphological wilting of plants, and （ii） defined DLWIF can be a promising indicator for a category of plants like zucchini.
文摘In this paper, the evaluation of stress intensity factor of plane crack problems for orthotropic plate of equal-parameter is investigated using a fractal two-level finite element method （F2LFEM）. The general solution of an orthotropic crack problem is obtained by assimilating the problem with isotropic crack problem, and is employed as the global interpolation function in F2LFEM. In the neighborhood of crack tip of the crack plate, the fractal geometry concept is introduced to achieve the similar meshes having similarity ratio less than one and generate an infinitesimal mesh so that the relationship between the stiffness matrices of two adjacent layers is equal. A large number of degrees of freedom around the crack tip are transformed to a small set of generalized coordinates. Numerical examples show that this method is efficient and accurate in evaluating the stress intensity factor （SIF）.
基金Project supported by the National Natural Science Foundation of China(No.11672150)the Beijing Nova Program Interdisciplinary Cooperation Project(No.xxjc201705)+1 种基金the Capital Clinical Special Promotion Project(No.Z161100000516233)the Key Issue of the 12th Five-Year Plan of People’s Liberation Army of China(No.BKJ13J004)
文摘This study investigates the viscoelastic behavior of soft bio-fibres in association with their fractal structures. A spring-dashpot fractal network with the self-similar topology, named the -type fractal ladder hyper-cell (FLHC), is abstracted from the micro/nano-structure of ligaments and tendons (LTs). Its constitutive operator is derived by the Heaviside operational calculus, which is of intrinsic fractional order. In terms of this operator, the long-term viscoelastic relaxation of bio-fibres arising from the fractal ladder topology is expounded. In addition, the fractional-order viscoelastic constitutive equation is obtained based on the FLHC of LTs, and its results are consistent with those of available human knee and spinal LT relaxation experiments. Results on the constitutive equation of FLHCs are formulated into two propositions. The multidisciplinary invariance and implications from the fractal ladder pattern of bio-fibres are also discussed.
文摘The theory of the fractal structure characterizing propagation of a crack through identification of its generator is presented. It’s generating fractal, the peculiarities of its construction and the way to measure its segments are defined, and a theorem on the inverse scale property of such and other of the axial symmetry property of the fractal generator are presented and demonstrated. The theory is applied on 6061-T6 aluminum samples, using SENB probes. Direction of crack propagation and its fractal dimension are calculated numerically. Results obtained from modeling the direction of crack propagation through mechanics of elastic linear fracture and the one proposed here, called geometrical fractal fracture, are compared, thus developing the mirror case.
文摘The purpose of this study is 1) to present a biomechanical model for evaluating the myogenic power expended in an arterial segment due to vascular smooth muscle contraction (VSMC) and 2) to assess the total power expenditure in the entire systemic arterial tree by utilizing the fractal nature of the branching architecture. The model is based on the mechanical equilibrium between the stretch stress exerted by blood pressure inside the vessel lumen and constricting stress elicited by VSMC in the vascular wall. An expression for myogenic power expenditure is formulated for a unit wall mass as a function of the internal vessel radius and extent of strain. This expression was then integrated over selected range of vessel radii, by taking into account of the fractal nature of the branching structure. When the total myogenic power expended in the systemic arterial tree in rat at the moderate strain level is converted to the oxygen consumption rate, it amounts to approximately 18% of the whole body oxygen consumption rate. This suggests that the mechanical power expenditure due to VSMC is a significant factor that should not be ignored in studies of vascular energetics.
