Motivated by a model of the response of vertically aligned carbon nanotube （VACNT） pillars in uniaxial compression, we consider the deformation of a class of compressible elastic-viscoplastic solids with a hardening...Motivated by a model of the response of vertically aligned carbon nanotube （VACNT） pillars in uniaxial compression, we consider the deformation of a class of compressible elastic-viscoplastic solids with a hardeningsoftening-hardening variation of flow strength with plastic strain. In previous work （Hutchens et al. 2011） a constitutive relation was presented and used to model the response of VACNT pillars in axisymmetric compression. Subsequently, it was found that due to a programming error the constitutive relation presented in the paper （Hutchens et al. 2011） was not the one actually implemented. In particular, the plastic flow rule actually used did not satisfy plastic normality. Here, we present the constitutive formulation actually implemented in the previous work （Hutchens et al. 2011）. Dynamic, finite deformation, finite element calculations are carried out for uniaxial compression, uniaxial tension and for indentation of a ＂half-space＂ by a conical indenter tip. A sequential buckling-like deformation mode is found in compression when there is plastic non-normality and hardening- softening-hardening. The same material characterization gives rise to a Lfiders band-like deformation mode in ten- sion. When there is a deformation mode with a sharp front along mesh boundaries, the overall stress-strain response contains high frequency oscillations that are a mesh artifact. The responses of non-softening solids are also analyzed and their overall stress-strain behavior and deformation modes are compared with those of hardening-softening- hardening solids. We find that indentation with a sharp indenter tip gives a qualitatively equivalent response for hardening and hardening-softening-hardening solids.展开更多
The study was made on the role of ozone (O3) gas treatment on seeds of Lycopersicon esculentum cv. PKM1 (tomato) to release dormancy in advance. The experimental conditions followed a complete factorial design with 3 ...The study was made on the role of ozone (O3) gas treatment on seeds of Lycopersicon esculentum cv. PKM1 (tomato) to release dormancy in advance. The experimental conditions followed a complete factorial design with 3 independent factors, i.e. A faster start of germination in T2 treatment (98% - 99%) was observed than in other treatments (T1, T3 and T4) compared to control seeds by measuring seedling growth rate on 5th day after treatment. Never the less a too long and high concentration of O3 treatment seemed to be penalizing on germination rate whereas low O3 concentration (T2) for a moderate time interval (20 min) seemed to be most beneficial. The treated seeds were stored, checked 1, 3, 6 months later and found that, the seeds have retained their accelerated germination efficiency. In particular 1T2 (1 month storage), 3T2 (3 month storage) had maximum germination rate among all the stored treated seeds, but 6T2 (6 month storage) didn’t show sustained germination acceleration efficiency. Therefore it was found that when time prolongs, O3 treatment loss its effect steadily and the germination efficiency of all the treatments are more or less same at six months after treatment. It is hypothesized that the application of O3 acts as an important phenomenon in accelerating seed germination by breaking the dormancy in advance which is associated with reduced level of ABA in O3 treated seeds.展开更多
基金supported by the Institute for Collaborative Biotechnologies through grant W911NF-09-0001 from the U.S.Army Research Office
文摘Motivated by a model of the response of vertically aligned carbon nanotube （VACNT） pillars in uniaxial compression, we consider the deformation of a class of compressible elastic-viscoplastic solids with a hardeningsoftening-hardening variation of flow strength with plastic strain. In previous work （Hutchens et al. 2011） a constitutive relation was presented and used to model the response of VACNT pillars in axisymmetric compression. Subsequently, it was found that due to a programming error the constitutive relation presented in the paper （Hutchens et al. 2011） was not the one actually implemented. In particular, the plastic flow rule actually used did not satisfy plastic normality. Here, we present the constitutive formulation actually implemented in the previous work （Hutchens et al. 2011）. Dynamic, finite deformation, finite element calculations are carried out for uniaxial compression, uniaxial tension and for indentation of a ＂half-space＂ by a conical indenter tip. A sequential buckling-like deformation mode is found in compression when there is plastic non-normality and hardening- softening-hardening. The same material characterization gives rise to a Lfiders band-like deformation mode in ten- sion. When there is a deformation mode with a sharp front along mesh boundaries, the overall stress-strain response contains high frequency oscillations that are a mesh artifact. The responses of non-softening solids are also analyzed and their overall stress-strain behavior and deformation modes are compared with those of hardening-softening- hardening solids. We find that indentation with a sharp indenter tip gives a qualitatively equivalent response for hardening and hardening-softening-hardening solids.
文摘The study was made on the role of ozone (O3) gas treatment on seeds of Lycopersicon esculentum cv. PKM1 (tomato) to release dormancy in advance. The experimental conditions followed a complete factorial design with 3 independent factors, i.e. A faster start of germination in T2 treatment (98% - 99%) was observed than in other treatments (T1, T3 and T4) compared to control seeds by measuring seedling growth rate on 5th day after treatment. Never the less a too long and high concentration of O3 treatment seemed to be penalizing on germination rate whereas low O3 concentration (T2) for a moderate time interval (20 min) seemed to be most beneficial. The treated seeds were stored, checked 1, 3, 6 months later and found that, the seeds have retained their accelerated germination efficiency. In particular 1T2 (1 month storage), 3T2 (3 month storage) had maximum germination rate among all the stored treated seeds, but 6T2 (6 month storage) didn’t show sustained germination acceleration efficiency. Therefore it was found that when time prolongs, O3 treatment loss its effect steadily and the germination efficiency of all the treatments are more or less same at six months after treatment. It is hypothesized that the application of O3 acts as an important phenomenon in accelerating seed germination by breaking the dormancy in advance which is associated with reduced level of ABA in O3 treated seeds.
