Modeling and Simulation of Pneumatic Impactor for Tubing Plugging

Tubing plugging often occurs and brings some difficulties to industrial production. This paper proposes a simple pneumatic impactor which can instantaneously generate great acceleration by a reservoir to shock and smash calcium monohydrate bonding in the tubing inwall. The working principle and the mathematical model of the impactor are introduced in detail. In order to obtain its dynamic characteristic, the simulation is performed. The results show that during the movement of the piston back pressure occurs due to the outlet chamber squeezed by the piston with a high speed, and with inlet pressure increasing positions of the piston with different peak velocities are almost the same. This impactor can be used to unplug tubings in oil or gas well.

Nomenclature of the functionally univentricular heart

Hearts which, at first sight, seem to have a solitary chamber within their ventricular mass have long been the subject of controversy. As difficult as it is to manage these cardiac malformations medically and surgically, it has been at least as challenging, to date, merely to describe and classify them. Even the most commonly used terms, “single ventricle” and “univentricular heart”, spark heated debate. In distant times, when congenitally malformed hearts were pathological curiosities, these entities were described as “cor triloculare biatriale”. Therein lies the beginning of the problem, since when hearts of this type were examined by more enlightened pathologists, such as the great Maude Abbott,1it became plain that the apparently solitary ventricular mass in reality possessed a second, albeit much smaller, chamber. Abbott described this second structure as the “outlet chamber”. This convention of describing a “single ventricle”, albeit with a co-existing “outlet chamber”, that presumably lacked ventricular status, continued throughout the first half of the twentieth century, although it had been recognised by then that hearts could rarely be found with truly solitary ventricles, and these were typically deemed to be common structures. Van Praagh et al.2neatly summarised the problem with this approach when they pointed out that the so-called “single ventricle” possessed two ventricular chambers, whilst the “common ventricle” described the truly solitary arrangement. In their seminal investigation of 1964, Van Praagh et al.2analysed only those hearts unified because of double inlet atrioventricular connection, or alignment. They excluded arbitrarily from their investigation all hearts with atrioventricular valvar atresia, despite the similarity in morphology between many of these latter lesions and the hearts with double inlet.3

Aerodynamic Performance of Rear Axial Compressor Stage With Annular Diffuser and Outlet Chamber

A detailed investigation of aerodynamic performance of three low-speed rear axial compressor stage bladings with the aspect ratios: 0.75, 1.0 and 1.25 was carried out. The bladings of industrial type consist of rotor, stator and outlet guide vanes. The outer and inner diameters of the stage are constant. The hub/tip ratio is 0.871 and the outer diameter is 800 mm. Stage blading is followed by an annular diffuser with outlet chamber. The effect of blade aspect ratio on compressor stage performance was also analysed with the use of straight cascade data. This data supported the test stage experimental results. We found that the effect of aspect ratio on stage performance is not remarkable in the considered range. There are some differences at off-design conditions. The lowest value of blading efficiency was obtained in the case with the lowest aspect ratio value. Three inlet velocity profiles were modelled with the use of lengthened inlet annulus and a screen specially designed. It was found that there is a significant effect of inlet velocity profile distortion on rear compressor stage blading performance for all aspect ratios. Aerodynamic characteristics of compressor stage blading with annular diffuser and outlet chamber were determined. During the investigation we also removed the outlet guide vanes. Therefore the effect of swirl and inlet velocity profile could be investigated.

Functional morphology of the olfactory organ of two carcharhinid shark species

The paired olfactory organs of both the lemon shark (Negaprion brevirostris) and the silky shark (Carcharhinus falciformis) are located in solid cartilaginous nasal capsules, which open at the ventral side of the snout and are entirely separate from the mouth. The olfactory rosette consists of two rows of lamellae arising from a central raphe. The lamellae possess secondary folds covered with sensory epithelium, which contains microvillous receptor cells, supporting cells with both cilia and microvilli, basal cells, and goblet cells. No ciliated receptor cells were found. Gaps between facing lamellae connect the inlet chamber with the outlet chamber. The inlet chamber receives the ventilatory water through the incurrent nostril and the outlet chamber discharges the water through the excurrent nostril. A nasal flap, a septum, and paired valve flaps form an incomplete barrier between incurrent and excurrent nostrils and may have hydrodynamic functions, which are discussed.