Dedicated Test Equipment Research Articles

Self-Expanding Stent and Delivery System for Aortic Valve Replacement

Currently, aortic valve replacement procedures require a sternotomy and use of cardiopulmonary bypass (CPB) to arrest the heart and provide a bloodless field in which to operate. A less invasive alternative to open heart surgery is transapical or transcatheter aortic valve replacement (TAVR), already emerging as a feasible treatment for patients with high surgical risk. The bioprosthetic valves are delivered via catheters using transarterial or transapical approaches and are implanted within diseased aortic valves. This paper reports the development of a new self-expanding stent for minimally invasive aortic valve replacement and its delivery device for the transapical approach under real-time magnetic resonance imaging (MRI) guidance. Made of nitinol, the new stent is designed to implant and embed a commercially available bioprosthetic aortic valve in aortic root. An MRI passive marker was affixed onto the stent and an MRI active marker to the delivery device. These capabilities were tested in ex vivo and in vivo experiments. Radial resistive force, chronic outward force, and the integrity of bioprosthesis on stent were measured through custom design dedicated test equipment. In vivo experimental evaluation was done using a porcine large animal model. Both ex vivo and in vivo experiment results indicate that the self-expanding stent provides adequate reinforcement of the bioprosthetic aortic valve and it is easier to implant the valve in the correct position. The orientation and positioning of the implanted valve is more precise and predictable with the help of the passive marker on stent and the active marker on delivery device. The new self-expanding nitinol stent was designed to exert a constant radial force and, therefore, a better fixation of the prosthesis in the aorta, which would result in better preservation of long-term heart function. The passive marker affixed on the stent and active marker embedded in the delivery devices helps to achieve precise orientation and positioning of the stent under MRI guidance. The design allows the stent to be retracted in the delivery device with a snaring catheter if necessary. Histopathology reports reveal that the stent is biocompatible and fully functional. All the stented bioprosthesis appeared to be properly seated in the aortic root.

Experimental Research on the Magnetic Field Sensitive Polymeric Actuator

Using domestic MFSP membrane as a medium of energy conversion, a kind of MFSP actuator was designed. The dedicated test equipment was constructed for experimental research, and the experimental results were given. The strip and circular MSFP membrane were analyzed qualitatively to obtain the deformation characteristics of membrane by finite element analysis software.

Audiometers—A Closer Look

Audiometers—A Closer Look

Crack propagation on helicopter panel: Experimental test and analysis

Aerospace structures need excellent structural efficiency and damage tolerant behaviour to avoid critical failure in presence of small defects and repeated small loads typical of contingent loads. With the aim of improving the performance of the structures, new materials have been developed. Such materials, as the Al–lithium alloy, are designed with the purpose of optimizing stress/strain vs. weight. Considering the distinct advantage, but also the disadvantage, of this innovative material, it is important to verify the damage tolerant behaviour of the component and this is the aim of the present work. With this aim, some tests have been performed on full scale panel specimens representative of a rear helicopter frame. Dedicated test equipment has been designed and built in order to apply the effective service loads on artificial damaged panels. During the tests, the propagation of the crack, started from an artificial damage, has been monitored until the progressive failure of the panel reaches one or more stringers. Moreover, each specimen has been instrumented with several strain gauges to obtain a strain map during the crack propagation. The crack parameters and the strains recorded during the propagation have been compared with the results from a detailed FE model and an analytical model, with a good correlation. In addition, a detailed FE submodel of the bolted joint (stringer and skin in the crack propagation path zone) has been constructed to obtain the crack parameter of a particular panel specimen whose test has also been carried out in the stringer bolted joint.

An all-digital DFT scheme for testing catastrophic faults in PLLs

Traditional functional testing of mixed-signal ICs is slow and requires costly, dedicated test equipment. The authors update the standard PLL architecture to allow simple digital testing. The all-digital strategy yields catastrophic fault coverage as high as that of the classical functional test, plus it is fast, extremely simple to implement, and requires only standard digital test equipment.

High‐temperature erosion tests on materials for fluidized bed combustor heat‐exchanger tubes

AbstractIn order to simulate and predict the erosion damage suffered by in‐bed tubes in fluidised bed combustors, dedicated test equipment was set up at CISE's tribology laboratory with ENEL S. p. A (Italian National Electricity Board) support. This erosion rig was used to test and characterise the behaviour of AISI 310, P9, and P22 steels, candidate materials for this type of heat‐exchanger tube. Tests were carried out at room temperature to characterise the erosion behaviour of these materials and at higher specimen (350°C and 500°C) and air (840°C) temperatures to simulate and characterise their behaviour in service. From this experimental work it turned out that, while at room temperature, the erosion behaviour of the three materials did not differ significantly, at high temperature P9 showed the best resistance in both test conditions and AISI 310 displayed an optimum behaviour at normal impact angles, but had the higher erosion rate at 30° impact angle.