To overcome the difficulty in directly measuring the impact force of a mechanical press, the inverse theory is employed to reconstruct the impact force from the corresponding response data in time domain. The nature o...To overcome the difficulty in directly measuring the impact force of a mechanical press, the inverse theory is employed to reconstruct the impact force from the corresponding response data in time domain. The nature of ill-posedness of impact force reconstruction is explored through singular value decomposition （SVD） and the Tikhonov regularization is utilized to deal with the ill-posedness, in which the optimal parameter is chosen in light of the L-curve criterion and the generalized cross- validation （GCV）. The experimentally measured strain responses of upper and lower dies of the press are chosen as source data for impact force reconstruction, and the corresponding numerical results are compared with the experimental measurements, which verifies the effectiveness of the reconstruction method.展开更多
The base stress of the opened bottom cylinder structure differs greatly from that of the structure with a closed bottom. By investigating the inner soil pressure on the cylinder wall and the base stress of the cylinde...The base stress of the opened bottom cylinder structure differs greatly from that of the structure with a closed bottom. By investigating the inner soil pressure on the cylinder wall and the base stress of the cylinder base, which were obtained from the model experiments, the interactions among the filler inside the cylinder, subsoil and cylinder are analyzed. The adjusting mechanism of frictional resistance between the inner filler and the wall of the cylinder during the overturning of the cylinder is discussed. Based on the experimental study, a method for calculating the base stress of the opened bottom cylinder structure is proposed. Meanwhile, the formulas for calculating the effective anti-overturning ratio of the opened bottom cylinder are derived.展开更多
Let {Si}li=1 be an iterated function system （IFS） on Rd with attractor K. Let π be the canonical projection. In this paper, we define a new concept called ＂projection pressure＂ Pπ（φ） for φ ∈（Rd） under cer...Let {Si}li=1 be an iterated function system （IFS） on Rd with attractor K. Let π be the canonical projection. In this paper, we define a new concept called ＂projection pressure＂ Pπ（φ） for φ ∈（Rd） under certain arlene IFS, and show the variational principle about the projection pressure. Furthermore, we check that the unique zero root of ＂projection pressure＂ still satisfies Bowen＇s equation when each Si is the similar map with the same compression ratio. Using the root of Bowen＇s equation, we can get the Hausdorff dimension of the attractor K.展开更多
In previous research, time-delay （△t） was a more important parameter than the reflection coefficient in the individual transfer function of central aortic pressure reconstruction. The At can be obtained by electroc...In previous research, time-delay （△t） was a more important parameter than the reflection coefficient in the individual transfer function of central aortic pressure reconstruction. The At can be obtained by electrocardiography （ECG） or phonocardiography （PCG）. Because the pre-ejection period remains an uncertain factor, the present study used ECG and PCG to define the delay time and analyzed the accuracy of the reconstruction results. The △tpre is the actual delay time derived from the aorta to the carotid pressure wave, △tpco is the time delay between the aortic valve component of the second heart sound and the dicrotic incisura of the carotid pressure wave, and AtEcc represents the delay from the interval of the ECG R-peak to the foot of the carotid pressure wave. Compared with the measured aortic pressure, the reconstruction result obtained by △t=△tpcslightly differed from the best result estimated by △t=△tpre. However, the differences between the result obtained by △t=△tEco and the best result were significant in terms of the diastolic blood pressure, and pulse pressure, and especially in terms of the augmentation index and root-mean-square-error. Thus, the At should be determined by PCG for central aortic pressure reconstruction in practice.展开更多
基金Transformation Program of Science and Technology Achievements of Jiangsu Province(No.BA2008030)
文摘To overcome the difficulty in directly measuring the impact force of a mechanical press, the inverse theory is employed to reconstruct the impact force from the corresponding response data in time domain. The nature of ill-posedness of impact force reconstruction is explored through singular value decomposition （SVD） and the Tikhonov regularization is utilized to deal with the ill-posedness, in which the optimal parameter is chosen in light of the L-curve criterion and the generalized cross- validation （GCV）. The experimentally measured strain responses of upper and lower dies of the press are chosen as source data for impact force reconstruction, and the corresponding numerical results are compared with the experimental measurements, which verifies the effectiveness of the reconstruction method.
文摘The base stress of the opened bottom cylinder structure differs greatly from that of the structure with a closed bottom. By investigating the inner soil pressure on the cylinder wall and the base stress of the cylinder base, which were obtained from the model experiments, the interactions among the filler inside the cylinder, subsoil and cylinder are analyzed. The adjusting mechanism of frictional resistance between the inner filler and the wall of the cylinder during the overturning of the cylinder is discussed. Based on the experimental study, a method for calculating the base stress of the opened bottom cylinder structure is proposed. Meanwhile, the formulas for calculating the effective anti-overturning ratio of the opened bottom cylinder are derived.
基金supported by National Natural Science Foundation of China (Grant No.10971100)National Basic Research Program of China (973 Program) (Grant No. 2007CB814800)
文摘Let {Si}li=1 be an iterated function system （IFS） on Rd with attractor K. Let π be the canonical projection. In this paper, we define a new concept called ＂projection pressure＂ Pπ（φ） for φ ∈（Rd） under certain arlene IFS, and show the variational principle about the projection pressure. Furthermore, we check that the unique zero root of ＂projection pressure＂ still satisfies Bowen＇s equation when each Si is the similar map with the same compression ratio. Using the root of Bowen＇s equation, we can get the Hausdorff dimension of the attractor K.
基金supported by the National Natural Science Foundation of China(81271737)
文摘In previous research, time-delay （△t） was a more important parameter than the reflection coefficient in the individual transfer function of central aortic pressure reconstruction. The At can be obtained by electrocardiography （ECG） or phonocardiography （PCG）. Because the pre-ejection period remains an uncertain factor, the present study used ECG and PCG to define the delay time and analyzed the accuracy of the reconstruction results. The △tpre is the actual delay time derived from the aorta to the carotid pressure wave, △tpco is the time delay between the aortic valve component of the second heart sound and the dicrotic incisura of the carotid pressure wave, and AtEcc represents the delay from the interval of the ECG R-peak to the foot of the carotid pressure wave. Compared with the measured aortic pressure, the reconstruction result obtained by △t=△tpcslightly differed from the best result estimated by △t=△tpre. However, the differences between the result obtained by △t=△tEco and the best result were significant in terms of the diastolic blood pressure, and pulse pressure, and especially in terms of the augmentation index and root-mean-square-error. Thus, the At should be determined by PCG for central aortic pressure reconstruction in practice.
