Abdominal aortic aneurysm is a common vascular disease that affects elderly population.Open surgical repair is regarded as the gold standard technique for treatment of abdominal aortic aneurysm,however,endovaseular an...Abdominal aortic aneurysm is a common vascular disease that affects elderly population.Open surgical repair is regarded as the gold standard technique for treatment of abdominal aortic aneurysm,however,endovaseular aneurysm repair has rapidly expanded since its first introduction in 1990s.As a less invasive technique,endovascular aneurysm repair has been confirmed to be an effective alternative to open surgical repair,especially in patients with co-morbid conditions.Computed tomography （CT） angiography is currently the preferred imaging modality for both preoperative planning and post-operative follow-up.2D CT images are complemented by a number of 3D reconstructions which enhance the diagnostic applications of CT angiography in both planning and follow-up of endovascular repair.CT has the disadvantage of high cummulative radiation dose,of particular concern in younger patients,since patients require regular imaging follow-ups after endovascular repair,thus,exposing patients to repeated radiation exposure for life.There is a trend to change from CT to ultrasound surveillance of endovascular aneurysm repair.Medical image visualizations demonstrate excellent morphological assessment of aneurysm and stent-grafts,but fail to provide hemodynamic changes caused by the complex stent-graft device that is implanted into the aorta.This article reviews the treatment options of abdominal aortic aneurysm,various image visualization tools,and follow-up procedures with use of different modalities including both imaging and computational fluid dynamics methods.Future directions to improve treatment outcomes in the follow-up of endovascular aneurysm repair are outlined.展开更多
Recently, Morabito(2010) has studied the water spray phenomena in planing hulls and presented new analytical equations. However, these equations have not been used for detailed parametric studies of water spray around...Recently, Morabito(2010) has studied the water spray phenomena in planing hulls and presented new analytical equations. However, these equations have not been used for detailed parametric studies of water spray around planing hulls. In this paper, a straight forward analysis is conducted to apply these analytical equations for finding the spray geometry profile by developing a computer program based on presented computational process. The obtained results of the developed computer program are compared against existing data in the literature and favorable accuracy is achieved. Parametric studies have been conducted for different physical parameters. Positions of spray apex are computed and three dimensional profiles of spray are examined. It is concluded that spray height increases by an increase in the speed coefficient or the deadrise angle. Ultimately, a computational process is added to Savitsky's method and variations of spray apex are computed for different velocities. It is shown that vertical, lateral, and longitudinal positions of spray increase as the craft speed increases. On the other hand, two new angles are defined in top view and it is concluded that they have direct relation with the trim angle. However, they show inverse relation with the deadrise angle.展开更多
This paper investigates the routing among autonomous systems (ASs) with quality of service (QoS) requirements. To avoid the intractability of the problem, abstract QoS capability must be informed among ASs, because th...This paper investigates the routing among autonomous systems (ASs) with quality of service (QoS) requirements. To avoid the intractability of the problem, abstract QoS capability must be informed among ASs, because the routhing which constrained QoS has been proved to be nondeterministic polynomial-time (NP) hard even inside an AS. This paper employs the modified Dijkstra algorithm to compute the maximum bottleneck bandwidth inside an AS. This approach lays a basis for the AS-level switching capability on which interdomain advertisement can be performed. Furthermore, the paper models the aggregated traffic in backbone network with fractional Brownian motion (FBM), and by integrating along the time axis in short intervals, a good estimation of the distribution of queue length in the next short intervals can be obtained. The proposed advertisement mechanism can be easily implemented with the current interdomain routing protocols. Numerical study indicates that the presented scheme is effective and feasible.展开更多
文摘Abdominal aortic aneurysm is a common vascular disease that affects elderly population.Open surgical repair is regarded as the gold standard technique for treatment of abdominal aortic aneurysm,however,endovaseular aneurysm repair has rapidly expanded since its first introduction in 1990s.As a less invasive technique,endovascular aneurysm repair has been confirmed to be an effective alternative to open surgical repair,especially in patients with co-morbid conditions.Computed tomography （CT） angiography is currently the preferred imaging modality for both preoperative planning and post-operative follow-up.2D CT images are complemented by a number of 3D reconstructions which enhance the diagnostic applications of CT angiography in both planning and follow-up of endovascular repair.CT has the disadvantage of high cummulative radiation dose,of particular concern in younger patients,since patients require regular imaging follow-ups after endovascular repair,thus,exposing patients to repeated radiation exposure for life.There is a trend to change from CT to ultrasound surveillance of endovascular aneurysm repair.Medical image visualizations demonstrate excellent morphological assessment of aneurysm and stent-grafts,but fail to provide hemodynamic changes caused by the complex stent-graft device that is implanted into the aorta.This article reviews the treatment options of abdominal aortic aneurysm,various image visualization tools,and follow-up procedures with use of different modalities including both imaging and computational fluid dynamics methods.Future directions to improve treatment outcomes in the follow-up of endovascular aneurysm repair are outlined.
文摘Recently, Morabito(2010) has studied the water spray phenomena in planing hulls and presented new analytical equations. However, these equations have not been used for detailed parametric studies of water spray around planing hulls. In this paper, a straight forward analysis is conducted to apply these analytical equations for finding the spray geometry profile by developing a computer program based on presented computational process. The obtained results of the developed computer program are compared against existing data in the literature and favorable accuracy is achieved. Parametric studies have been conducted for different physical parameters. Positions of spray apex are computed and three dimensional profiles of spray are examined. It is concluded that spray height increases by an increase in the speed coefficient or the deadrise angle. Ultimately, a computational process is added to Savitsky's method and variations of spray apex are computed for different velocities. It is shown that vertical, lateral, and longitudinal positions of spray increase as the craft speed increases. On the other hand, two new angles are defined in top view and it is concluded that they have direct relation with the trim angle. However, they show inverse relation with the deadrise angle.
文摘This paper investigates the routing among autonomous systems (ASs) with quality of service (QoS) requirements. To avoid the intractability of the problem, abstract QoS capability must be informed among ASs, because the routhing which constrained QoS has been proved to be nondeterministic polynomial-time (NP) hard even inside an AS. This paper employs the modified Dijkstra algorithm to compute the maximum bottleneck bandwidth inside an AS. This approach lays a basis for the AS-level switching capability on which interdomain advertisement can be performed. Furthermore, the paper models the aggregated traffic in backbone network with fractional Brownian motion (FBM), and by integrating along the time axis in short intervals, a good estimation of the distribution of queue length in the next short intervals can be obtained. The proposed advertisement mechanism can be easily implemented with the current interdomain routing protocols. Numerical study indicates that the presented scheme is effective and feasible.
