a mathematical analysis has been carried out for the axial flow of a bingham plastic fluid, in the concentric cylinder viscometer which consists of a cylindrical sample holder (the cup) and a cylindrical spindle (the bob) coaxial with the cup. the fluid to be tested flows through the annular gap of the cup and the bob system, sheared by the rotation of the inner cylinder, while the outer cylind...

A theoretical investigation has been made of core-annular flow: the flow of a high-viscosity liquid core surrounded by a low-viscosity annular liquid layer through a horizontal pipe. Special attention is paid to the question how the buoyancy force on the core, caused by a possible density difference between the core and the annular layer, is counterbalanced. From earlier studies it is known tha...

oil production optimization is one of the main targets of reservoir management. smart well technology gives the ability of real time oil production optimization. although this technology has many advantages; optimum adjustment or sizing of corresponding valves is still an issue to be solved. in this research, optimum port sizing of inflow control devices (icds) which are passive control valves ...

2542 B ioprosthetic valves are increasingly used in patients with aortic stenosis. Compared with mechanical valves, bio-prosthetic valves are associated with a lower risk of thrombo-embolic events and do not require long-term anticoagulation. 1,2 However, bioprosthetic valves have limited durability; the best current valves can be expected to degenerate within 10 to 20 years, resulting in steno...

OBJECTIVES The aim of this study was to evaluate a strategy of intentional underexpansion of excessively oversized balloon-expandable transcatheter heart valves (THVs) in terms of clinical outcomes, valve function, and frame durability at 1 year. BACKGROUND Transcatheter aortic valve replacement requires the selection of an optimally sized THV to ensure paravalvular sealing and fixation witho...

Flow maldistribution, resulting from bubbles or other particulate matter, can lead to drastic performance degradation in devices that employ parallel microchannels for heat transfer. In this work, direct numerical simulations of fluid flow through a prescribed parallel microchannel geometry are performed and coupled with active control of actuated microvalves to effectively identify and reduce ...

I read with interest the article by Kurazumi and colleagues about mitral valve replacement for a severely calcified annulus [1]. I congratulate the authors for their excellent results and simple technique to overcome this difficult problem. My only concern is about the valve size of 21 mm in the mitral position producing about 2 cm mitral valve area. This might be marginal for small-body-weight...

This paper studies local valve control of the electro-hydraulic system. The sluggish response of hydraulic control valve usually becomes the bottleneck of whole system performance. Although fast valves (e.g. high-bandwidth servovalves) are available, they are far more expensive than slow valves (e.g. proportional directional control valves). To improve the performance of proportional directiona...

The rate-controlled production (RCP) inflow control devices (ICDs) are valves placed in the lower completion of oil and gas wells, capable autonomously controlling reservoir inflow. This technology self-regulates undesired phases, such as water, by choking flow after breakthrough event, thus improving recovery factor reducing water production. In this context, article presents a numerical study...