Aim-To evaluate the relationship between histopathology results and magnetic resonance imaging (MRI) on in-and opposed-phase sequences grading of fat deposition within human liver. Materials and methods-In-and opposed...Aim-To evaluate the relationship between histopathology results and magnetic resonance imaging (MRI) on in-and opposed-phase sequences grading of fat deposition within human liver. Materials and methods-In-and opposed-phase T1-weighted gradient-echo sequences (double echo time 2.3 ms and 4.6ms)were performed in 25 patients,using a 1.5-T clinical MR imaging system. Fat/water ratio on in-and opposed-phase images of the liver was compared with pathologically defined degree or steatosis. The signal intensity in the images was acquired with operator-defined regions of interest at the same location in both fat and water images and the ratio was calculated by dividing signal intensity of liver in opposed phased sequence on signal intensity of liver in phased sequence. Fat/water ratio and the degree of steatosis were compared using linear regression. The sensitivity and specificity of opposed-phase for diagnosing steatosis were defined by ROC analysis. Furthermore, a correlation between visual signal intensity variation (SIV)and the degree of steatosis was assessed using Pearson correlation coefficient. Results-Histology demonstrated fatty liver infiltrations in 81 %of specimens. The percentage of fatty hepatocytes was 28 +/-30 %. Fat/water ratio was significantly correlated with the pathologic grading of steatosis (r = 0.816, P < 0.001). The opposed phase MR imaging sensibility and specificity for the diagnosis of hepatic steatosis were respectively 80%and 71%. We obtained a statistically significant correlation between visual SIV and fatty liver grading (P = 0.017). Conclusion-We demonstrated a significant correlation between fat/water ratio and histological findings for the detection and grading of fatty liver.展开更多
Magnetorheological （MR） dampers have been proposed to control the vibration of offshore platforms in this paper. The semi-active control strategy based on fuzzy control algorithm was adopted to determine the optimal...Magnetorheological （MR） dampers have been proposed to control the vibration of offshore platforms in this paper. The semi-active control strategy based on fuzzy control algorithm was adopted to determine the optimal output control force based on the responses of jacket platforms. A typical jacket platform in Mexico Gulf was selected as the numerical example to investigate the effectiveness of the proposed control method. Furthermore, a model experiment was performed to validate the results of the numerical simulation. The experimental model of the jacket platform was designed based on dynamical similarity criterion by the scale of 1：50. Both of the numerical and experimental results show that the semi-active control system with the MR damper can reduce vibrations of jacket platforms effectively and at the same time the control effect is stable.展开更多
Magneto-rheological (MR) fluid-based dampers are currently being explored for their potential implementation in intelligent vehicle suspension designs. Due to inherent hysteretic force properties of the MR dampers, an...Magneto-rheological (MR) fluid-based dampers are currently being explored for their potential implementation in intelligent vehicle suspension designs. Due to inherent hysteretic force properties of the MR dampers, analyzing and suppressing the MR-damper hysteresis effects, therefore, impose a great challenge. A quarter-vehicle MR-suspension model is formulated in conjunction with proposed hysteretic and mean MR-damper models, and the passive and semi-actively controlled MR-suspension systems are focused to investigate the influence of MR-damper force hysteresis. The semi-actively controlled MR-suspension employs the “on-off” control law in response to direction of the damper velocity, so as to generate the asymmetric damping force property form the symmetric MR-damper design. The results show that the MR-damping hysteresis yields serious transients and oscillations in responses for the semi-actively controlled MR-suspension than the passive MR-suspension due to the current-switching discontinuity, and would thus deteriorate the suspension performance. The undesired strong transients and oscillations in responses can be effectively suppressed by employing the proposed smooth technique without phase shift for modulating the command current discontinuity.展开更多
Objective：To investigate the relationship between renal blood distribution and the physiological activities of the kidney. Methods：A mathematical model is developed based on response （MR） Hagan-Poiseuille law and ...Objective：To investigate the relationship between renal blood distribution and the physiological activities of the kidney. Methods：A mathematical model is developed based on response （MR） Hagan-Poiseuille law and mass transport, coupling mechanics of myogenic tubuloglomerular feedback （TGF） and the tubular system in the renal medulla. The model parameters, including the permeability coefficients, the vascular lumen radius and the solute concentration at the inlet of the tubes, are derived from the experimental results. Simulations of the blood and water flow in the loop of Henel, the collecting duct and vas rectum, are carried out by the model of the tubular system in the renal medulla, based on conservations of water and solutes for transmural transport. Then the tubular model is coupled with MR and TGF mechanics. Results：The results predict the dynamics of renal autoregulation on its blood pressure and flow, and the distributions are 88.5% in the cortex, 10.3% in the medulla, and 1.2% at papilla,respectively. The fluid flow and solute concentrations along the tubules and vasa recta are obtained. Conclusion ：The present model could assess renal functions qualitatively and quantitatively and provide a methodological approach for clinical research.展开更多
文摘Aim-To evaluate the relationship between histopathology results and magnetic resonance imaging (MRI) on in-and opposed-phase sequences grading of fat deposition within human liver. Materials and methods-In-and opposed-phase T1-weighted gradient-echo sequences (double echo time 2.3 ms and 4.6ms)were performed in 25 patients,using a 1.5-T clinical MR imaging system. Fat/water ratio on in-and opposed-phase images of the liver was compared with pathologically defined degree or steatosis. The signal intensity in the images was acquired with operator-defined regions of interest at the same location in both fat and water images and the ratio was calculated by dividing signal intensity of liver in opposed phased sequence on signal intensity of liver in phased sequence. Fat/water ratio and the degree of steatosis were compared using linear regression. The sensitivity and specificity of opposed-phase for diagnosing steatosis were defined by ROC analysis. Furthermore, a correlation between visual signal intensity variation (SIV)and the degree of steatosis was assessed using Pearson correlation coefficient. Results-Histology demonstrated fatty liver infiltrations in 81 %of specimens. The percentage of fatty hepatocytes was 28 +/-30 %. Fat/water ratio was significantly correlated with the pathologic grading of steatosis (r = 0.816, P < 0.001). The opposed phase MR imaging sensibility and specificity for the diagnosis of hepatic steatosis were respectively 80%and 71%. We obtained a statistically significant correlation between visual SIV and fatty liver grading (P = 0.017). Conclusion-We demonstrated a significant correlation between fat/water ratio and histological findings for the detection and grading of fatty liver.
基金Supported by the National Natural Science Foundation of China （NSFC-5060900）.
文摘Magnetorheological （MR） dampers have been proposed to control the vibration of offshore platforms in this paper. The semi-active control strategy based on fuzzy control algorithm was adopted to determine the optimal output control force based on the responses of jacket platforms. A typical jacket platform in Mexico Gulf was selected as the numerical example to investigate the effectiveness of the proposed control method. Furthermore, a model experiment was performed to validate the results of the numerical simulation. The experimental model of the jacket platform was designed based on dynamical similarity criterion by the scale of 1：50. Both of the numerical and experimental results show that the semi-active control system with the MR damper can reduce vibrations of jacket platforms effectively and at the same time the control effect is stable.
文摘Magneto-rheological (MR) fluid-based dampers are currently being explored for their potential implementation in intelligent vehicle suspension designs. Due to inherent hysteretic force properties of the MR dampers, analyzing and suppressing the MR-damper hysteresis effects, therefore, impose a great challenge. A quarter-vehicle MR-suspension model is formulated in conjunction with proposed hysteretic and mean MR-damper models, and the passive and semi-actively controlled MR-suspension systems are focused to investigate the influence of MR-damper force hysteresis. The semi-actively controlled MR-suspension employs the “on-off” control law in response to direction of the damper velocity, so as to generate the asymmetric damping force property form the symmetric MR-damper design. The results show that the MR-damping hysteresis yields serious transients and oscillations in responses for the semi-actively controlled MR-suspension than the passive MR-suspension due to the current-switching discontinuity, and would thus deteriorate the suspension performance. The undesired strong transients and oscillations in responses can be effectively suppressed by employing the proposed smooth technique without phase shift for modulating the command current discontinuity.
文摘Objective：To investigate the relationship between renal blood distribution and the physiological activities of the kidney. Methods：A mathematical model is developed based on response （MR） Hagan-Poiseuille law and mass transport, coupling mechanics of myogenic tubuloglomerular feedback （TGF） and the tubular system in the renal medulla. The model parameters, including the permeability coefficients, the vascular lumen radius and the solute concentration at the inlet of the tubes, are derived from the experimental results. Simulations of the blood and water flow in the loop of Henel, the collecting duct and vas rectum, are carried out by the model of the tubular system in the renal medulla, based on conservations of water and solutes for transmural transport. Then the tubular model is coupled with MR and TGF mechanics. Results：The results predict the dynamics of renal autoregulation on its blood pressure and flow, and the distributions are 88.5% in the cortex, 10.3% in the medulla, and 1.2% at papilla,respectively. The fluid flow and solute concentrations along the tubules and vasa recta are obtained. Conclusion ：The present model could assess renal functions qualitatively and quantitatively and provide a methodological approach for clinical research.
