Background: Long standing aortic stenosis leads to elevated left ventricular (LV) pressure and as a result LV hypertrophy and myocardial fibrosis shall increase. The left ventricular ejection fraction (EF) usually rem...Background: Long standing aortic stenosis leads to elevated left ventricular (LV) pressure and as a result LV hypertrophy and myocardial fibrosis shall increase. The left ventricular ejection fraction (EF) usually remains adequately-preserved until advanced and late stages of aortic stenosis. But the preserved muscle of the LV is only limited to a portion of the entire myocardium. Speckle tracking echocardiography has proved its superiority to the standard two-dimensional echocardiography method in the detection of Left Ventricular (LV) function. Global Longitudinal strain (GLS) is considered as the most robust myocardial strain component.?Objective: The aim of the study is to assess the early course of left ventricular reverse remodelling after Transcutaneous Aortic Valve Implantation (TAVI) in patients with symptomatic severe aortic valve stenosis.?Methods: 50 patients with severe symptomatic valvular aortic stenosis undergoing TAVI as decided by the heart team after comprehensive discussion.?Standard transthoracic echocardiography including Doppler analysis was performed. 2D speckle-tracking strain assessment of Global radial, circumferential and longitudinal strain at parasternal mid-ventricular short-axis view (at the level of papillary muscle) and from the apical long-axis, two-chamber and four-chamber views with a frame rate between 40 and 80 frames per second. Tracing of endocardial borders was done. Patients with significant coronary artery disease were fully revascularized by percutaneous coronary intervention prior to the study and the procedure. Results: 23 (46%) patients were males, while 27 (54%) were females. The patients’ stratification according to comorbidities/associated risk factors revealed that 54% of the patients had DM, 86% were hypertensive, 38% had chronic kidney disease (CKD), and 32% had a previous percutaneous coronary intervention (PCI).?The mean age for our study participants ranged?from 60 to 92 years (Mean ± SD = 76.60 ± 5.96). Left ventricular diastolic diameter (LVDd) was 44展开更多
A hierarchical control framework is applied for the distributed cooperative vehicular platoon using vehicular ad-hoc networks.The parameter-space-approach-based cooperative adaptive cruise control(CACC)controller is p...A hierarchical control framework is applied for the distributed cooperative vehicular platoon using vehicular ad-hoc networks.The parameter-space-approach-based cooperative adaptive cruise control(CACC)controller is proposed to guarantee the D-stability and the string stability considering the influence of the communication time delay and time lag of vehicular dynamic performance.This CACC controller combines the feedforward loop of the acceleration of the preceding vehicle with the feedback loop of the following errors,in which the gain of the feedforward loop is designed to decrease matching errors and the gains of the feedback loop are selected from the feasible region in the parameter space.To verify the effectiveness of the CACC controller,a six-vehicle platoon with a simplified vehicular dynamic is simulated under speed-up and stop scenarios.The simulation results demonstrate that the disturbance is attenuated along with the platoon and the following errors are convergent with well-designed convergent performance.A CarSim/Simulink co-simulation is designed to further verify the effectiveness of the hierarchical control framework and the rationality of the CACC controller in the real vehicular platoon application.The simulation results under the highway fuel economy test drive cycle show that the CACC controller improves the drive comfort and significantly decreases the following errors.展开更多
Echocardiography is the most common diagnostic method for assessing atrial function but the technique has some limitations. Traditionally, assessment of left atrial function has been performed by measuring volumes wit...Echocardiography is the most common diagnostic method for assessing atrial function but the technique has some limitations. Traditionally, assessment of left atrial function has been performed by measuring volumes with 2D echocardiography. Additionally, it can be assessed with transmitral Doppler and pulmonary vein Doppler. Recently, an alternative method has been incorporated, namely, measurement of myocardial deformation with color tissue Doppler-derived strain. However, this method has several limitations, such as suboptimal reproducibility, angle-dependence, signal artifacts and the fact that it only measures regional strain and does not obtain information about the curved portion of the atrial roof. To overcome these limitations in the quantification of atrial function, the use of speckle tracking echocardiography (STE) strain has been proposed. This technique is not derived from Doppler but rather from 2D echocardiography; it is angle-independent and allows one to measure global as well as regional atrial strain. In this editorial, we describe the physical and pathophysiological concepts of STE and underline the clinical usefulness of this new technique.展开更多
The current research of autonomous vehicle motion control mainly focuses on trajectory tracking and velocity tracking. However, numerous studies deal with trajectory tracking and velocity tracking separately, and the ...The current research of autonomous vehicle motion control mainly focuses on trajectory tracking and velocity tracking. However, numerous studies deal with trajectory tracking and velocity tracking separately, and the yaw stability is seldom considered during trajectory tracking. In this research, a combination of the longitudinal–lateral control method with the yaw stability in the trajectory tracking for autonomous vehicles is studied. Based on the vehicle dynamics, considering the longitudinal and lateral motion of the vehicle, the velocity tracking and trajectory tracking problems can be attributed to the longitudinal and lateral control. A sliding mode variable structure control method is used in the longitudinal control. The total driving force is obtained from the velocity error in order to carry out velocity tracking. A linear time-varying model predictive control method is used in the lateral control to predict the required front wheel angle for trajectory tracking. Furthermore, a combined control framework is established to control the longitudinal and lateral motions and improve the reliability of the longitudinal and lateral direction control. On this basis, the driving force of a tire is allocated reasonably by using the direct yaw moment control, which ensures good yaw stability of the vehicle when tracking the trajectory. Simulation results indicate that the proposed control strategy is good in tracking the reference velocity and trajectory and improves the performance of the stability of the vehicle.展开更多
文摘Background: Long standing aortic stenosis leads to elevated left ventricular (LV) pressure and as a result LV hypertrophy and myocardial fibrosis shall increase. The left ventricular ejection fraction (EF) usually remains adequately-preserved until advanced and late stages of aortic stenosis. But the preserved muscle of the LV is only limited to a portion of the entire myocardium. Speckle tracking echocardiography has proved its superiority to the standard two-dimensional echocardiography method in the detection of Left Ventricular (LV) function. Global Longitudinal strain (GLS) is considered as the most robust myocardial strain component.?Objective: The aim of the study is to assess the early course of left ventricular reverse remodelling after Transcutaneous Aortic Valve Implantation (TAVI) in patients with symptomatic severe aortic valve stenosis.?Methods: 50 patients with severe symptomatic valvular aortic stenosis undergoing TAVI as decided by the heart team after comprehensive discussion.?Standard transthoracic echocardiography including Doppler analysis was performed. 2D speckle-tracking strain assessment of Global radial, circumferential and longitudinal strain at parasternal mid-ventricular short-axis view (at the level of papillary muscle) and from the apical long-axis, two-chamber and four-chamber views with a frame rate between 40 and 80 frames per second. Tracing of endocardial borders was done. Patients with significant coronary artery disease were fully revascularized by percutaneous coronary intervention prior to the study and the procedure. Results: 23 (46%) patients were males, while 27 (54%) were females. The patients’ stratification according to comorbidities/associated risk factors revealed that 54% of the patients had DM, 86% were hypertensive, 38% had chronic kidney disease (CKD), and 32% had a previous percutaneous coronary intervention (PCI).?The mean age for our study participants ranged?from 60 to 92 years (Mean ± SD = 76.60 ± 5.96). Left ventricular diastolic diameter (LVDd) was 44
基金supported by the Jilin Province Key Technology and Development Program(No.20190302077GX)the National Key Technologies R&D Program of China during the 13th Five-Year Plan Period(No.2017YFC0601604).
文摘A hierarchical control framework is applied for the distributed cooperative vehicular platoon using vehicular ad-hoc networks.The parameter-space-approach-based cooperative adaptive cruise control(CACC)controller is proposed to guarantee the D-stability and the string stability considering the influence of the communication time delay and time lag of vehicular dynamic performance.This CACC controller combines the feedforward loop of the acceleration of the preceding vehicle with the feedback loop of the following errors,in which the gain of the feedforward loop is designed to decrease matching errors and the gains of the feedback loop are selected from the feasible region in the parameter space.To verify the effectiveness of the CACC controller,a six-vehicle platoon with a simplified vehicular dynamic is simulated under speed-up and stop scenarios.The simulation results demonstrate that the disturbance is attenuated along with the platoon and the following errors are convergent with well-designed convergent performance.A CarSim/Simulink co-simulation is designed to further verify the effectiveness of the hierarchical control framework and the rationality of the CACC controller in the real vehicular platoon application.The simulation results under the highway fuel economy test drive cycle show that the CACC controller improves the drive comfort and significantly decreases the following errors.
文摘Echocardiography is the most common diagnostic method for assessing atrial function but the technique has some limitations. Traditionally, assessment of left atrial function has been performed by measuring volumes with 2D echocardiography. Additionally, it can be assessed with transmitral Doppler and pulmonary vein Doppler. Recently, an alternative method has been incorporated, namely, measurement of myocardial deformation with color tissue Doppler-derived strain. However, this method has several limitations, such as suboptimal reproducibility, angle-dependence, signal artifacts and the fact that it only measures regional strain and does not obtain information about the curved portion of the atrial roof. To overcome these limitations in the quantification of atrial function, the use of speckle tracking echocardiography (STE) strain has been proposed. This technique is not derived from Doppler but rather from 2D echocardiography; it is angle-independent and allows one to measure global as well as regional atrial strain. In this editorial, we describe the physical and pathophysiological concepts of STE and underline the clinical usefulness of this new technique.
基金Supported by National Natural Science Foundation of China(Grant Nos.51575103,11672127,U1664258)Fundamental Research Funds for the Central Universities of China(Grant No.NT2018002)+1 种基金China Postdoctoral Science Foundation(Grant Nos.2017T100365,2016M601799)the Fundation of Graduate Innovation Center in NUAA(Grant No.k j20180207)
文摘The current research of autonomous vehicle motion control mainly focuses on trajectory tracking and velocity tracking. However, numerous studies deal with trajectory tracking and velocity tracking separately, and the yaw stability is seldom considered during trajectory tracking. In this research, a combination of the longitudinal–lateral control method with the yaw stability in the trajectory tracking for autonomous vehicles is studied. Based on the vehicle dynamics, considering the longitudinal and lateral motion of the vehicle, the velocity tracking and trajectory tracking problems can be attributed to the longitudinal and lateral control. A sliding mode variable structure control method is used in the longitudinal control. The total driving force is obtained from the velocity error in order to carry out velocity tracking. A linear time-varying model predictive control method is used in the lateral control to predict the required front wheel angle for trajectory tracking. Furthermore, a combined control framework is established to control the longitudinal and lateral motions and improve the reliability of the longitudinal and lateral direction control. On this basis, the driving force of a tire is allocated reasonably by using the direct yaw moment control, which ensures good yaw stability of the vehicle when tracking the trajectory. Simulation results indicate that the proposed control strategy is good in tracking the reference velocity and trajectory and improves the performance of the stability of the vehicle.
