The intrinsic relationships between energy dissipation,energy release,strength and abrupt structural failure are key to understanding the evolution of deformational processes in rocks.Theoretical and experimental stud...The intrinsic relationships between energy dissipation,energy release,strength and abrupt structural failure are key to understanding the evolution of deformational processes in rocks.Theoretical and experimental studies confirm that energy plays an important role in rock deformation and failure.Dissipated energy from external forces produces damage and irreversible deformation within rock and decreases rock strength over time.Structural failure of rocks is caused by an abrupt release of strain energy that manifests as a catastrophic breakdown of the rock under certain conditions.The strain energy released in the rock volume plays a pivotal role in generating this abrupt structural failure in the rocks.In this paper,we propose criteria governing（1） the deterioration of rock strength based on energy dissipation and（2） the abrupt structural failure of rocks based on energy release.The critical stresses at the time of abrupt structural failure under various stress states can be determined by these criteria.As an example,the criteria have been used to analyze the failure conditions of surrounding rock of a circular tunnel.展开更多
Five different parts of Rosa damascene Mill. twigs were treated with hormone solution （50 mg/L NAA＋100 mg/L IBA） and planted in base material. After 50 d of growth, the survival rate and rooting condition were inve...Five different parts of Rosa damascene Mill. twigs were treated with hormone solution （50 mg/L NAA＋100 mg/L IBA） and planted in base material. After 50 d of growth, the survival rate and rooting condition were investigated. The results showed that the survival rate from 5 different parts of cutting stem decreased from top to bottom （upper 98.22%, middle and upper 95.12%, middle 91.10%, middle and lower 72.90%, lower 71.12%）. The same results were also observed in the number, total length and fresh weight of secondary roots of cutting segments from different parts of twigs.展开更多
The volume-selected MRS of rat brain was performed on a 200 MHz broad horizontal-bore nuclear magnetic resonance imaging spectrometer. The localized proton spectroscopy of rat brain was acquired using the double spin-...The volume-selected MRS of rat brain was performed on a 200 MHz broad horizontal-bore nuclear magnetic resonance imaging spectrometer. The localized proton spectroscopy of rat brain was acquired using the double spin-echo pulse sequence (PRESS) to select the position and size of the volume. Water signal was suppressed by CHESS sequence which was composed of chemical shift selective rf pulses and dephasing gradients. The parameter TE was taken as 40 ms and 135 ms in the experiment. The localized MRS of the rat brain with the status of live and death was obtained in various TE values. Results showed that volume-selected proton MRS of the rat brain in vivo with longer TE consisted mainly of signals produced by N-acetylaspartate (NAA), creatine (Cre), choline (Cho) and the lactate spectral peak occurred in the MRS of the rat brain ex vivo. On the other hand, the MRS of the rat brain with shorter TE contained glutamine/glutamate and lipid signals besides those signals mentioned previously. Although the information abstracted from the MRS of the rat brain with shorter TE may be more than that with longer TE, the spectral resolution of the MRS with shorter TE was slightly worse. In addition, it might indicate that the absolute concentration of NAA was decreased in dead rat brain because the SNR of NAA peak in the MRS ex vivo got lower.展开更多
基金Supported by the State Key Basic Research Development Program of China (2002CB412705,2010CB226804) the National Natural Science Foundation of China (50579042,10802092)
文摘The intrinsic relationships between energy dissipation,energy release,strength and abrupt structural failure are key to understanding the evolution of deformational processes in rocks.Theoretical and experimental studies confirm that energy plays an important role in rock deformation and failure.Dissipated energy from external forces produces damage and irreversible deformation within rock and decreases rock strength over time.Structural failure of rocks is caused by an abrupt release of strain energy that manifests as a catastrophic breakdown of the rock under certain conditions.The strain energy released in the rock volume plays a pivotal role in generating this abrupt structural failure in the rocks.In this paper,we propose criteria governing（1） the deterioration of rock strength based on energy dissipation and（2） the abrupt structural failure of rocks based on energy release.The critical stresses at the time of abrupt structural failure under various stress states can be determined by these criteria.As an example,the criteria have been used to analyze the failure conditions of surrounding rock of a circular tunnel.
文摘Five different parts of Rosa damascene Mill. twigs were treated with hormone solution （50 mg/L NAA＋100 mg/L IBA） and planted in base material. After 50 d of growth, the survival rate and rooting condition were investigated. The results showed that the survival rate from 5 different parts of cutting stem decreased from top to bottom （upper 98.22%, middle and upper 95.12%, middle 91.10%, middle and lower 72.90%, lower 71.12%）. The same results were also observed in the number, total length and fresh weight of secondary roots of cutting segments from different parts of twigs.
文摘The volume-selected MRS of rat brain was performed on a 200 MHz broad horizontal-bore nuclear magnetic resonance imaging spectrometer. The localized proton spectroscopy of rat brain was acquired using the double spin-echo pulse sequence (PRESS) to select the position and size of the volume. Water signal was suppressed by CHESS sequence which was composed of chemical shift selective rf pulses and dephasing gradients. The parameter TE was taken as 40 ms and 135 ms in the experiment. The localized MRS of the rat brain with the status of live and death was obtained in various TE values. Results showed that volume-selected proton MRS of the rat brain in vivo with longer TE consisted mainly of signals produced by N-acetylaspartate (NAA), creatine (Cre), choline (Cho) and the lactate spectral peak occurred in the MRS of the rat brain ex vivo. On the other hand, the MRS of the rat brain with shorter TE contained glutamine/glutamate and lipid signals besides those signals mentioned previously. Although the information abstracted from the MRS of the rat brain with shorter TE may be more than that with longer TE, the spectral resolution of the MRS with shorter TE was slightly worse. In addition, it might indicate that the absolute concentration of NAA was decreased in dead rat brain because the SNR of NAA peak in the MRS ex vivo got lower.
