When flying at hypersonic speeds, it is a fundamental requirement to reduce the high drag resulting from a blunt nose cone in the ascent stage to increase the payload weight on the one hand and decrease the amount of energy needed to overcome the Earth’s gravity on the other. However, an aerospike can be attached on the front of the nose cone to obtain a high drag and heat load reduction. This study describes novel technique of an active flow control concepton nose cone with aerodisk that uses counterflowing jets to significantly modify external flowfields. In fact, this method strongly disperse the shock waves of supersonic and hypersonic vehicles to reduce aerothermal loads.Numerical simulations of a 2D axisymmetric aerodisked nose cone in hypersonic flow are conducted, and innovative techniques involving forward injection of gas from the stagnation point of the sphere are investigated; techniques include injection of various counterflowing jets (Helium and Carbon dioxide) as a coolant jet from the nose cone behind the aerodisk. In this study, the characteristics of the various jet conditions of a counterflowing jet on a cone surface were investigated numerically to improve performance of the jet on heat reduction at surface of a nose. Different Mach numbers at different altitudes have been chosen to investigate the effect of the aerospike on the nose cone’s surrounding flowfield. The drag and the heat load reduction is numerically evaluated at Mach numbers of 5.75. The results show that the lighter gas, Helium, is found to have a better cooling performance than Carbon Dioxide in low pressure ratios. The film cooling of Helium jet due to its lower specific heat capacity (Cp) character is efficient on heat load of the nose cone.
A 41-year-old man presented with a 7-year history of gradually increasing right proptosis and a 2-year history of decreased vision and limited eye movements. Right proptosis (11 mm), limitation of movement in all gazes, anisocoria, and visual impairment implied orbital apex compression. Computed tomography showed several distinct lesions with mild delayed enhancement extending to the orbital apex. Through a lateral orbitotomy, 10 discrete hemangiomas were removed uneventfully. Histopathologic findings were consistent with cavernous hemangioma in all tumors removed. Proptosis resolved after surgery at 3 to 4 weeks. Visual acuity was unchanged (20/25), and eye movement significantly improved at last follow-up, 15 months after surgery.
Chaotic vibration has been identified in the flexible automotive wiper blade at certain wiping speeds. This irregular vibration not only decreases the wiping efficiency, but also degrades the driving comfort. A reliable nonlinear system identification namely nonlinear auto regressive exogenous Elman neural network (NARXENN) was adopted in first stage of this survey to model the flexible dynamics of wiper blade with acquired experimental data. In controller design part, taking into account environmental and external disturbances that cause changes in the dynamic characteristics of the system demanded a robust controller to make a trade off between the worst and best scenario. An active fuzzy force controller (AFLC) supervised by multi objective genetic algorithm (MOGA) is developed to keep both interests of noise and vibration redaction of automobile wiper blade at the reasonable rise time.
The implantation of intravascular stent is a kind of coronary angioplasty to restore the blood flow perfusion to the downstream of the heart muscle tissue. Stent implantation is a mechanical procedure, the success of which depends to a good understanding of its mechanical behavior during the deployment. Computational studies may be used to investigate the mechanical behavior of stents and to determine the biomechanical interaction between the stent and the artery in a stenting procedure. The aim of this paper is to investigate the expansion characteristics of a certain stent as it is deployed and implanted in an artery containing a plaque, and try to reach to a model close to a real condition of stent implantation. Unlike most of the models proposed in the literature, all the steps of the deployment of a stent in the stenotic vessel (i.e. pressure increasing, constant load pressure and pressure decreasing) are simulated in this paper to show the behavior of stent in different stages of implantation. Results include stress distribution, radial gain, outer diameter changes, dogboning and foreshortening. According to the findings, the first step of deployment, i.e. pressure increasing, play a main role in the success of stent implantation.
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