Shape memory effect is capability of certain materials to recover its original shape after an apparently permanent deformation. The NiTi alloy of the composition is approximately equiatomic and it is the materials tha...Shape memory effect is capability of certain materials to recover its original shape after an apparently permanent deformation. The NiTi alloy of the composition is approximately equiatomic and it is the materials that exhibit the best characteristics for application of these properties, especially in the biomedical area, because of their excellent biocompatibility as： in the manufacture of medical and dental instruments, orthodontic wires, orthopedic materials, guide wires, stents, filters and components to realize the less invasive surgeries. In other areas, they are used for confections of electronic keys, spectacle frames, application in controllers, junction of pipes and electronic connectors among others. New research topics involving the application of these alloys super-elasticity are also known as pseudo elasticity. This event has an isothermal nature and involves the storage of potential energy in the shape memory effect and super-elasticity. In this context, this work falls within the scope of use of the technologies being an example of the work undertaken, in the course Graduate of Federal University of Pernambuco in skills in these technologies. It will present the results of a heat engine which engine element is a helical spring made of a NiTi alloy equiatomic with memory effect reversibly. The spring is triggered by a hot source （- 373.15 K） and a cold source （273.15 K）. The machine is capable of producing a reciprocating oscillating between the two sources. Heat equations and the equations that describe the dynamic behavior of the spring were developed. Through the development of dynamic equations, it can determine the minimum mass for the motion of the machine, as well as the instantaneous and average power and overall efficiency. You can check the functionality of the machine by way of the inclination angle of the propeller and the coefficient of static friction. Among the main results, it was observed that the overall performance of the machine compared to the machines of this category showed the feasibility of the project.展开更多
Hemodynamic characteristics such as blood velocity,blood pressure,flow impingement,wall shear stress and oscillatory shear index are considered to play important roles in the initiation,growth,rupture and recurrence o...Hemodynamic characteristics such as blood velocity,blood pressure,flow impingement,wall shear stress and oscillatory shear index are considered to play important roles in the initiation,growth,rupture and recurrence of the cerebral aneurysms.Endovascular therapy is widely implemented to treat the cerebral aneurysms by releasing coils into the aneurysm sac for limiting the blood flow to the sac and stent-assisted coil embolization is adopted to occlude the wide-necked or complex aneurysms.Some researchers believe that stents are not only a mechanical device but may act as a biological system and contribute to vessel wall healing.Hemodynamics simulation helps people understand the effect of hemodynamic characteristics on the recurrence of the coiled aneurysm and it also benefits the interventional planning of neurosurgeons.This study constructed the numerical model for a subject-specific ICA aneurysm treated with stent-assisted coil embolization,which combined the coiled model of the aneurysm with a porous stent placement,and simulated the pulsatile blood flow in these aneurysm models.When a stent was placed across the aneurysm orifice in the coiled aneurysm,the high wall shear stress around the distal aneurysm root was reduced more than that of the coiled aneurysm without a stent.The simulated results point to the conclusion that the stent not only protects the parent artery from occlusion due to extension of coils or thrombosis,but may also reduce the recurrence risk of the stent-assisted coiled aneurysm.展开更多
文摘Shape memory effect is capability of certain materials to recover its original shape after an apparently permanent deformation. The NiTi alloy of the composition is approximately equiatomic and it is the materials that exhibit the best characteristics for application of these properties, especially in the biomedical area, because of their excellent biocompatibility as： in the manufacture of medical and dental instruments, orthodontic wires, orthopedic materials, guide wires, stents, filters and components to realize the less invasive surgeries. In other areas, they are used for confections of electronic keys, spectacle frames, application in controllers, junction of pipes and electronic connectors among others. New research topics involving the application of these alloys super-elasticity are also known as pseudo elasticity. This event has an isothermal nature and involves the storage of potential energy in the shape memory effect and super-elasticity. In this context, this work falls within the scope of use of the technologies being an example of the work undertaken, in the course Graduate of Federal University of Pernambuco in skills in these technologies. It will present the results of a heat engine which engine element is a helical spring made of a NiTi alloy equiatomic with memory effect reversibly. The spring is triggered by a hot source （- 373.15 K） and a cold source （273.15 K）. The machine is capable of producing a reciprocating oscillating between the two sources. Heat equations and the equations that describe the dynamic behavior of the spring were developed. Through the development of dynamic equations, it can determine the minimum mass for the motion of the machine, as well as the instantaneous and average power and overall efficiency. You can check the functionality of the machine by way of the inclination angle of the propeller and the coefficient of static friction. Among the main results, it was observed that the overall performance of the machine compared to the machines of this category showed the feasibility of the project.
基金supported by the National Natural Science Foundation of China (Grant Nos. 30772234 and 30870707)
文摘Hemodynamic characteristics such as blood velocity,blood pressure,flow impingement,wall shear stress and oscillatory shear index are considered to play important roles in the initiation,growth,rupture and recurrence of the cerebral aneurysms.Endovascular therapy is widely implemented to treat the cerebral aneurysms by releasing coils into the aneurysm sac for limiting the blood flow to the sac and stent-assisted coil embolization is adopted to occlude the wide-necked or complex aneurysms.Some researchers believe that stents are not only a mechanical device but may act as a biological system and contribute to vessel wall healing.Hemodynamics simulation helps people understand the effect of hemodynamic characteristics on the recurrence of the coiled aneurysm and it also benefits the interventional planning of neurosurgeons.This study constructed the numerical model for a subject-specific ICA aneurysm treated with stent-assisted coil embolization,which combined the coiled model of the aneurysm with a porous stent placement,and simulated the pulsatile blood flow in these aneurysm models.When a stent was placed across the aneurysm orifice in the coiled aneurysm,the high wall shear stress around the distal aneurysm root was reduced more than that of the coiled aneurysm without a stent.The simulated results point to the conclusion that the stent not only protects the parent artery from occlusion due to extension of coils or thrombosis,but may also reduce the recurrence risk of the stent-assisted coiled aneurysm.
