Butterfly valve is a flow control device, which is used to regulate the fluid flowing through a piping system. Analysis and optimization are of special importance in the design and usage of butterfly valves. A proper selection of a Butterfly valve would require the knowledge of its characteristics and robustness. Normally this information used to be obtained from experimental tests. However the...

OBJECTIVE To evaluate the performance of manual resuscitators (MRs) used in Brazil in accordance with international standards. METHODS Using a respiratory system simulator, four volunteer physiotherapists employed eight MRs (five produced in Brazil and three produced abroad), which were tested for inspiratory and expiratory resistance of the patient valve; functioning of the pressure-limiting...

purpose: to evaluate the early and intermediate outcomes of ahmed glaucoma valve implantation in pediatric glaucoma at labbafinejad medical center. methods: this was a retrospective chart review of 101 eyes of 80 consecutive patients with pediatric glaucoma who underwent ahmed glaucoma valve implantation. success was defined as an intraocular pressure less than 21 mmhg with or without medicatio...

purpose: to evaluate the effect of early aqueous suppressants initiation on ahmed glaucoma valve success rate. methods: in this randomized clinical trial, a total of 94 eyes of 94 patients with refractory glaucoma were enrolled. the eyes were randomly selected into 2 groups. in group 1 (n=47), patients received early topical combination of timolol-dorzolamide twice daily after ahmed glaucoma va...

Background and aim of the study: The study aim was to determine the effect of mitral saddle annulus and leaflet length on peak leaflet stress and transmitral flow pattern when utilizing a novel bileaflet bioprosthetic valve. Methods: A novel valve, which closely mimics the saddle annulus motion of the mitral valve was developed. A series of computational analyses and in-vitro hemodynamic studie...

BACKGROUND AND AIM OF THE STUDY In-vitro studies on the ATS heart valve have indicated that valve opening is less in an expanding conduit than in a straight conduit. METHODS Bileaflet valve behavior was studied using a new computational fluid-structure interaction model. A three-dimensional model of the ATS valve was studied in two geometries, simulating the valve in a geometry with sudden ex...

High-pressure fluctuation and flow ripple may cause unexpected vibration noise when the piston pump works under severe conditions, eventually lead to hydraulic transmission failure. The geometry of valve plate has a great influence on pressure chamber. In order optimize structure plate, mathematical model considering slot leakage lubricating interfaces was established in this paper. used invest...

Intraoperative transesophageal echocardiography is now used routinely during aortic valve replacement, allowing immediate evaluation of replaced or repaired valves. It is well recognised that high transvalvular pressure gradients can be detected immediately after implantation of a prosthetic aortic valve which may be due to multifactorial confounding variables, including functional phenomena, p...

The control valve operates at high operation frequency (up to 1,000 Hz) in the large pressure differences between the inlet and outlet of the valve. The flow and operation characteristics of a high-speed electromagnetic control valve are investigated using a commercial software, CFD-ACE+. It is found that maximum operation frequency of the control valve depends on the applied electromagnetic fo...

The paper presents the CFD model of a load sensing directional control valve. was validated experimentally in terms pressure drop and flow force at different positions spool. spool position imposed manually by means micrometric screw cell used for measuring force. developed with CAD-embedded tool FloEFD®. has been proved to be very reliable estimating drop, moreover quite good results were obta...