The ratio of expectation crossings of dielectric elastomer balloon excited by random pressure is analytically evaluated in this letter. The Mooney-Rivlin model is adopted to describe the constitutive relation while th...The ratio of expectation crossings of dielectric elastomer balloon excited by random pressure is analytically evaluated in this letter. The Mooney-Rivlin model is adopted to describe the constitutive relation while the random pressure is described by Gaussian white noise. Through a specific transformation, the stochastic differential equations for the total energy and phase are derived. With the application of the stochastic averaging, the system total energy is then approximated by a one-dimensional diffusion pro-cess. Solving the associated Fokker-Planck-Kolmogorov （FPK） equation yields the stationary probability density of the system total energy. The ratio of expectation crossings is then derived based on the joint stationary probability density of stretch ratio and its ratio of change. The efficacy and accuracy of the proposed procedure are verified by comparing with the results from Monte Carlo simulation （MCS）.展开更多
Objective: To establish an objective criterion for assessing brain tolerance to carotid artery occlusion. Methods Endovascular trial balloon occlusion of carotid artery (TBO) in combination with single-photon emission...Objective: To establish an objective criterion for assessing brain tolerance to carotid artery occlusion. Methods Endovascular trial balloon occlusion of carotid artery (TBO) in combination with single-photon emission computed tomography (SPECT), transcranial Doppler ultrasonography (TCD) and carotid artery stump pressure (SP) measurement was performed routinely for those patients who might have carotid artery manipulated or permanently occluded. Results Out of the 10 cases, one failed the TBO, though an angiographically adequate collateral circulation was observed. The patient’s SP and relative symmetry (rS) of SPECT imaging were 51mmHg and 86%. The remaining cases showed negative TBOs. After carotid occlusions, their mean velocity of ipsilateral middle cerebral artery decreased (16. 3 ± 6. 9 )%. The mean rS was (98. 0 ± 2. 4)% (92. 7% -101. 3% ). The mean SP was (64. 5 ± 13. 0)mmHg [(72. 3±11. 3)% of baseline, range 32-83mmHg. For one subject, the ICA was occluded spontaneously in the test. A reversal internal carotid artery (ICA ) flow was noted in 3 patients with balloon inflated in the common carotid artery (CCA ). When the CCA was occluded, the system blood pressure and heart rate increased apparently. However, this phenomenon did not occur when the ballon was inflated in the ICA. Conclusion With this TBO technique, clinically silent areas of decreased perfusion might be detected. We suggest it be a routine examination prior to carotid manipulations.展开更多
基金supported by the National Natural Science Foundation of China(11672262,11472240,11532011,and 11621062)
文摘The ratio of expectation crossings of dielectric elastomer balloon excited by random pressure is analytically evaluated in this letter. The Mooney-Rivlin model is adopted to describe the constitutive relation while the random pressure is described by Gaussian white noise. Through a specific transformation, the stochastic differential equations for the total energy and phase are derived. With the application of the stochastic averaging, the system total energy is then approximated by a one-dimensional diffusion pro-cess. Solving the associated Fokker-Planck-Kolmogorov （FPK） equation yields the stationary probability density of the system total energy. The ratio of expectation crossings is then derived based on the joint stationary probability density of stretch ratio and its ratio of change. The efficacy and accuracy of the proposed procedure are verified by comparing with the results from Monte Carlo simulation （MCS）.
文摘Objective: To establish an objective criterion for assessing brain tolerance to carotid artery occlusion. Methods Endovascular trial balloon occlusion of carotid artery (TBO) in combination with single-photon emission computed tomography (SPECT), transcranial Doppler ultrasonography (TCD) and carotid artery stump pressure (SP) measurement was performed routinely for those patients who might have carotid artery manipulated or permanently occluded. Results Out of the 10 cases, one failed the TBO, though an angiographically adequate collateral circulation was observed. The patient’s SP and relative symmetry (rS) of SPECT imaging were 51mmHg and 86%. The remaining cases showed negative TBOs. After carotid occlusions, their mean velocity of ipsilateral middle cerebral artery decreased (16. 3 ± 6. 9 )%. The mean rS was (98. 0 ± 2. 4)% (92. 7% -101. 3% ). The mean SP was (64. 5 ± 13. 0)mmHg [(72. 3±11. 3)% of baseline, range 32-83mmHg. For one subject, the ICA was occluded spontaneously in the test. A reversal internal carotid artery (ICA ) flow was noted in 3 patients with balloon inflated in the common carotid artery (CCA ). When the CCA was occluded, the system blood pressure and heart rate increased apparently. However, this phenomenon did not occur when the ballon was inflated in the ICA. Conclusion With this TBO technique, clinically silent areas of decreased perfusion might be detected. We suggest it be a routine examination prior to carotid manipulations.
