Study on the Regulating Performance of Sliding Regulation-Valve

Science.gov (United States)

Hu, Wei; Peng, Xiaoyong; Zhang, Yuan; Zheng, Yulan; Zhu, Fangyao

2018-01-01

Using a proven reliable method of CFD to study the regulating performance of a sliding regulation valve with a conical spool and rugby body. The numerical simulation results indicate that no matter where the spool is located, the flow field always has a vortex at the center of the valve body; When the spool is at the origin, the vortex and resistance coefficient of the valve are the minimum; When the spool moves from the origin to the right (the opening of the valve becomes smaller) to reach a certain position later, vortex currents also begin to appear around the tube wall behind the orifice. In addition, the vortex increases as the throttling port decreases whereas the resistance coefficient of the valve ascends slowly with the increase of the deviation of the spool and the rise in series; This type of regulating valve has S type (slow at both ends, sensitive at the center) flow characteristics at the stroke, and is not affected by the size of Re.

Internal leakage detection in control valves; Detektion der inneren Leckage von Stellgeraeten

Energy Technology Data Exchange (ETDEWEB)

Kiesbauer, J. [SAMSON AG, Mess- und Regeltechnik, Frankfurt am Main (Germany). Entwicklungspruefstand; Hoffmann, H. [SAMSON AG, Mess- und Regeltechnik, Frankfurt am Main (Germany). Bereich Entwicklung

2000-07-01

Digital positioners offer a number of interesting features regarding improved process plant reliability and maintenance or servicing. This can provide the basis for using software tools for early fault diagnosis and performance visualization of control valves with extended functions, such as archiving the control valve's condition when new. It can be subjected to trend analyses as well as to preventative maintenance and servicing while in operation. Up to now, such systems cannot reliably predict the possible increase in internal leakage. Predictions can only be made about a possible change in the actuator's closing force and the zero point when the valve is closed. This article introduces a new and cost-effective leakage detector for control valves in combination with the binary input of a digital positioner which can signal the increase in internal leakage in the throttling area (e.g. caused by wear on the throttling element) of a control valve, if the valve is closed during operation. (orig.) [German] Digitale Stellungsregler bieten eine Reihe von interessanten Moeglichkeiten im Hinblick auf die Verbesserung der Prozesszuverlaessigkeit und der Wartung bzw. Instandhaltung. Auf dieser Basis koennen Softwaretools zur Fehlerfrueherkennung und zur Performance-Visualisierung bei Stellgeraeten mit weitergehender Funktionalitaet eingesetzt werden. Diese unterstuetzen z.B. die Archivierung des Neuzustandes des Stellgeraetes sowie die vorbeugende Wartung und Instandhaltung im laufenden Prozess bis hin zu Trendanalysen. Solche Systeme koennen bisher allerdings noch keine zuverlaessigen Aussagen ueber die eventuelle Zunahme der inneren Leckage machen. Aussagen sind nur moeglich ueber eventuelle Veraenderungen der Antriebsschliesskraft und des Nullpunktes bei geschlossenem Ventil. Dieser Beitrag stellt einen neuartigen kostenguenstigen Leckagedetektor fuer Stellgeraete in Kombination mit dem Binaereingang eines digitalen Stellungsreglers vor, welcher die erhoehte

Manual Manipulation of Engine Throttles for Emergency Flight Control

Science.gov (United States)

Burcham, Frank W., Jr.; Fullerton, C. Gordon; Maine, Trindel A.

2004-01-01

If normal aircraft flight controls are lost, emergency flight control may be attempted using only engines thrust. Collective thrust is used to control flightpath, and differential thrust is used to control bank angle. Flight test and simulation results on many airplanes have shown that pilot manipulation of throttles is usually adequate to maintain up-and-away flight, but is most often not capable of providing safe landings. There are techniques that will improve control and increase the chances of a survivable landing. This paper reviews the principles of throttles-only control (TOC), a history of accidents or incidents in which some or all flight controls were lost, manual TOC results for a wide range of airplanes from simulation and flight, and suggested techniques for flying with throttles only and making a survivable landing.

DEPENDENCE OF AIR SPRING PARAMETERS ON THROTTLE RESISTANCE

Directory of Open Access Journals (Sweden)

O. H. Reidemeister

2016-04-01

Full Text Available Purpose. In this paper it is necessary to conduct: 1 research and analyse the influence of throttle element pneumatic resistance on elastic and damping parameters of air spring; 2 to obtain the dependence of air spring parameters on throttle element pneumatic resistance value. Methodology. The work presents the elaborated model of the air spring as a dynamic system with three phase coordinates (cylinder pressure, auxiliary reservoir pressure, cylinder air mass. Stiffness and viscosity coefficients were determined on the basis of system response to harmonic kinematic disturbance. The data for the analysis are obtained by changing the capacity of the connecting element and the law of pressure variation between the reservoir and the cylinder. The viscosity coefficient is regarded as the viscosity ratio of the hydraulic damper, which for one oscillation cycle consumes the same energy as the air spring. The process of air condition change inside the cylinder (reservoir is considered to be adiabatic; the mass air flow through the connecting element depends on the pressure difference. Findings. We obtained the curves for spring viscosity and stiffness coefficients dependence on the throttle resistance at three different laws, linking airflow through the cylinder with the pressure difference in cylinder and reservoir. At both maximum and minimum limiting resistance values the spring viscosity tends to zero, reaching its peak in the mean resistance values. Stiffness increases monotonically with increasing resistance, tends to the limit corresponding to the absence of an auxiliary reservoir (at high resistance and the increase in cylinder volume by the reservoir volume (at low resistance. Originality.The designed scheme allows determining the optimal parameters of elastic and damping properties of the pneumatic system as function of the throttle element air resistance. Practical value.The ability to predict the parameters of elastic and damping properties

Utilization of the heat of mixing in open-circuit throttle refrigerators

International Nuclear Information System (INIS)

Zhakharov, N.D.; Anikeev, G.N.; Grezin, A.K.

1986-01-01

Open-circuit throttle refrigerators based on gas mixtures operate, as a rule, according to a single-stream scheme. The refrigerating effect is determined by the isothermal throttling effect of the mixture in the cylinder under the conditions at the inlet to the cryogenic unit. The authors use the heat of mixing of the cryogenic mixtures to increase the available refrigerating effect. Data are presented on mixtures of nitrogen and Freon-13; the thermodynamic properties of these compounds have been investigated experimentally over a wide range of parameters. It was found that in the case of correct selection of the scheme and complex optimization of the parameters, two-stream throttle refrigerators exceed the single-stream throttle refrigerators by at least a factor of 1.5 with respect to relative useful energy. With account taken of the design, technological, and operational parameters, that which is most promising is the scheme with mixing of the components in reverse flow

Exergy analysis on throttle reduction efficiency based on real gas equations

International Nuclear Information System (INIS)

Luo, Yuxi; Wang, Xuanyin

2010-01-01

This paper proposes an approach to calculate the efficiency of throttling in which the exergy (available energy) is used to evaluate the energy conversion processes. In the exergy calculation for real gases, a difficult part of integration can be removed by judiciously advised thermodynamic paths; the compressibility factor is calculated by using Peng-Robinson (P-R) equation. It is found that the largest deviation between the exergies calculated by the real gas equation and ideal gas assumption is about 1%. Because the exergy is a function of the pressure and temperature, the Joule-Thomson coefficients are used to calculate the temperature changes of throttling, based on the compressibility factors of the Soave-Redlich-Kwong (S-R-K) and P-R equations, and the temperature decreases are compared with those calculated by empirical formula. The result shows that the heat exergy contributes very little in throttling. The simple equation of ideal gas is suggested to calculate the efficiency of throttling for air at atmospheric temperatures.

Effect of swirl on the performance and combustion of a biogas fuelled spark ignition engine

International Nuclear Information System (INIS)

Porpatham, E.; Ramesh, A.; Nagalingam, B.

2013-01-01

Highlights: • Tests were conducted on a biogas fuelled SI engine with normal and masked valve. • Improvement in brake power and brake thermal efficiency with masked valve. • Lean misfire limit is extended with enhanced swirl from 0.68 to 0.65. • Enhanced swirl decreases HC level from1530 ppm to 1340 ppm and increases NO emission from 2250 ppm to 3440 ppm. • The reduction in ignition delay and higher heat release rate with enhanced swirl. - Abstract: The influence of swirl on the performance, emissions and combustion in a constant speed Spark Ignition (SI) engine was studied experimentally. A single cylinder diesel engine was modified to operate as a biogas operated spark ignition engine. The engine was operated at 1500 rpm at throttle opening of 25% and 100% at various equivalence ratios. The tests covered a range of equivalence ratios from rich to lean operating limits and also at an optimum compression ratio of 13:1 with normal and masked intake valve to enhance swirl. The spark timing was set to MBT (Minimum advance for Best Torque). It was found that masked valve configuration enhanced the power output and brake thermal efficiency at full throttle. The lean limit of combustion also got extended. Heat release rates indicated enhanced combustion rates with masked valve, which are mainly responsible for the improvement in thermal efficiency. NO level increased with masked valve as compared to normal configuration. The spark timings were to be retarded by about 6 °CA and 4 °CA when compared to normal configuration at 25% and 100% throttle respectively

Northrop Grumman TR202 LOX/LH2 Deep Throttling Engine Project Status

Science.gov (United States)

Gromski, J.; Majamaki, A. N.; Chianese, S. G.; Weinstock, V. D.; Kim, T.

2010-01-01

NASA's Propulsion and Cryogenic Advanced Development (PCAD) project is currently developing enabling propulsion technologies in support of the Exploration Initiative, with a particular focus on the needs of the Altair Project. To meet Altair requirements, several technical challenges need to be overcome, one of which is the ability for the lunar descent engine(s) to operate over a deep throttle range with cryogenic propellants. To address this need, PCAD has enlisted Northrop Grumman Aerospace Systems (NGAS) in a technology development effort associated with the TR202, a LOX/LH2 expander cycle engine driven by independent turbopump assemblies and featuring a variable area pintle injector similar to the injector used on the TR200 Apollo Lunar Module Descent Engine (LMDE). Since the Apollo missions, NGAS has continued to mature deep throttling pintle injector technology. The TR202 program has completed two phases of pintle injector testing. The first phase of testing used ablative thrust chambers and demonstrated igniter operation as well as stable performance at several power levels across the designed 10:1 throttle range. The second phase of testing was performed on a calorimeter chamber and demonstrated injector performance at various power levels (75%, 50%, 25%, 10%, and 7.5%) across the throttle range as well as chamber heat flux to show that the engine can close an expander cycle design across the throttle range. This paper provides an overview of the TR202 program. It describes the different phases of the program with the key milestones of each phase. It then shows when those milestones were met. Next, it describes how the test data was used to update the conceptual design and how the test data has created a database for deep throttling cryogenic pintle technology that is readily scaleable and can be used to again update the design once the Altair program's requirements are firm. The final section of the paper describes the path forward, which includes

Application of 5-Fluorouracil-Polycaprolactone Sustained-Release Film in Ahmed Glaucoma Valve Implantation Inhibits Postoperative Bleb Scarring in Rabbit Eyes.

Science.gov (United States)

Bi, Xiu-Zeng; Pan, Wei-Hua; Yu, Xin-Ping; Song, Zong-Ming; Ren, Zeng-Jin; Sun, Min; Li, Cong-Hui; Nan, Kai-Hui

2015-01-01

This study was designed to investigate whether 5-fluorouracil (5-Fu)-polycaprolactone sustained-release film in Ahmed glaucoma valve implantation inhibits postoperative bleb scarring in rabbit eyes. Eighteen New Zealand white rabbits were randomly divided into three groups (A, B and C; n = 6 per group). Group A received combined 5-Fu-polycaprolactone sustained-release film application and Ahmed glaucoma valve implantation, group B received local infiltration of 5-Fu and Ahmed glaucoma valve implantation, and group C received Ahmed glaucoma valve implantation. Postoperative observations were made of the anterior segment, intraocular pressure, central anterior chamber depth, blebs, drainage tube, and accompanying ciliary body detachment. The pathology of the blebs and surrounding tissues were observed at month 3 postoperatively. We revealed that the 5-Fu-polycaprolactone sustained-release film maintained a release concentration range of 13.7 ± 0.12 to 37.41 ± 0.47 μg/ml over three months in vitro. Postoperatively, diffuse blebs with ridges were found in all eyes in group A, two blebs were observed in group B, and no bleb formation was present in group C. The postoperative central anterior chamber depth in group A was significantly less than that of the other two groups. The postoperative intraocular pressure of group A stabilized at 6.33-8.67 mmHg, whereas that of group C gradually remained at 7.55-10.02 mmHg. The histopathology showed that the fibrous tissue thickness of the blebs in group A was significantly thinner than that of the other groups. We conclude that the 5-Fu-polycaprolactone sustained-release film had a sustained drug release effect, which promoted the inhibition of bleb scarring after Ahmed glaucoma valve implantation.

Flow-throttling orifice nozzle

International Nuclear Information System (INIS)

Sletten, H.L.

1975-01-01

A series-parallel-flow type throttling apparatus to restrict coolant flow to certain fuel assemblies of a nuclear reactor is comprised of an axial extension nozzle of the fuel assembly. The nozzle has a series of concentric tubes with parallel-flow orifice holes in each tube. Flow passes from a high pressure plenum chamber outside the nozzle through the holes in each tube in series to the inside of the innermost tube where the coolant, having dissipated most of its pressure, flows axially to the fuel element. (U.S.)

Northrop Grumman TR202 LOX/LH2 Deep Throttling Engine Technology Project Status

Science.gov (United States)

Gromski, Jason; Majamaki, Annik; Chianese, Silvio; Weinstock, Vladimir; Kim, Tony S.

2010-01-01

NASA's Propulsion and Cryogenic Advanced Development (PCAD) project is currently developing enabling propulsion technologies in support of future lander missions. To meet lander requirements, several technical challenges need to be overcome, one of which is the ability for the descent engine(s) to operate over a deep throttle range with cryogenic propellants. To address this need, PCAD has enlisted Northrop Grumman Aerospace Systems (NGAS) in a technology development effort associated with the TR202 engine. The TR202 is a LOX/LH2 expander cycle engine driven by independent turbopump assemblies and featuring a variable area pintle injector similar to the injector used on the TR200 Apollo Lunar Module Descent Engine (LMDE). Since the Apollo missions, NGAS has continued to mature deep throttling pintle injector technology. The TR202 program has completed two series of pintle injector testing. The first series of testing used ablative thrust chambers and demonstrated igniter operation as well as stable performance at discrete points throughout the designed 10:1 throttle range. The second series was conducted with calorimeter chambers and demonstrated injector performance at discrete points throughout the throttle range as well as chamber heat flow adequate to power an expander cycle design across the throttle range. This paper provides an overview of the TR202 program, describing the different phases and key milestones. It describes how test data was correlated to the engine conceptual design. The test data obtained has created a valuable database for deep throttling cryogenic pintle technology, a technology that is readily scalable in thrust level.

ThrottleBot - Performance without Insight

OpenAIRE

Chang, Michael Alan; Panda, Aurojit; Tsai, Yuan-Cheng; Wang, Hantao; Shenker, Scott

2017-01-01

Large scale applications are increasingly built by composing sets of microservices. In this model the functionality for a single application might be split across 100s or 1000s of microservices. Resource provisioning for these applications is complex, requiring administrators to understand both the functioning of each microservice, and dependencies between microservices in an application. In this paper we present ThrottleBot, a system that automates the process of determining what resource wh...

Investigation of the Flow Rate Effect Upstream of the Constant-Geometry Throttle on the Gas Mass Flow

Directory of Open Access Journals (Sweden)

Yu. M. Timofeev

2016-01-01

Full Text Available The turbulent-flow throttles are used in pneumatic systems and gas-supply ones to restrict or measure gas mass flow. It is customary to install the throttles in joints of pipelines (in teejoints and cross tees or in joints of pipelines with pneumatic automation devices Presently, in designing the pneumatic systems and gas-supply ones a gas mass flow through a throttle is calculated by a known equation derived from the Saint-Venant-Vantсel formula for the adiabatic flow of ideal gas through a nozzle from an unrestrictedly high capacity tank. Neglect of gas velocity at the throttle inlet is one of the assumptions taken in the development of the above equation. As may be seen in practice, in actual systems the diameters of the throttle and the pipe wherein it is mounted can be commensurable. Neglect of the inlet velocity therewith can result in an error when determining the required throttle diameter in design calculation and a flow rate in checking calculation, as well as when measuring a flow rate in the course of the test. The theoretical study has revealed that the flow velocity at the throttle inlet is responsible for two parameter values: the outlet flow velocity and the critical pressure ratio, which in turn determine the gas mass flow value. To calculate the gas mass flow, the dependencies are given in the paper, which allow taking into account the flow rate at the throttle inlet. The analysis of obtained dependencies has revealed that the degree of influence of inlet flow rate upon the mass flow is defined by two parameters: pressure ratio at the throttle and open area ratio of the throttle and the pipe wherein it is mounted. An analytical investigation has been pursued to evaluate the extent to which the gas mass flow through the throttle is affected by the inlet flow rate. The findings of the investigation and the indications for using the present dependencies are given in this paper. By and large the investigation allowed the

Lyapunov-based constrained engine torque control using electronic throttle and variable cam timing

NARCIS (Netherlands)

Feru, E.; Lazar, M.; Gielen, R.H.; Kolmanovsky, I.V.; Di Cairano, S.

2012-01-01

In this paper, predictive control of a spark ignition engine equipped with an electronic throttle and a variable cam timing actuator is considered. The objective is to adjust the throttle angle and the engine cam timing in order to reduce the exhaust gas emissions while maintaining fast and

Bioprosthetic Valve Fracture Improves the Hemodynamic Results of Valve-in-Valve Transcatheter Aortic Valve Replacement.

Science.gov (United States)

Chhatriwalla, Adnan K; Allen, Keith B; Saxon, John T; Cohen, David J; Aggarwal, Sanjeev; Hart, Anthony J; Baron, Suzanne J; Dvir, Danny; Borkon, A Michael

2017-07-01

Valve-in-valve (VIV) transcatheter aortic valve replacement (TAVR) may be less effective in small surgical valves because of patient/prosthesis mismatch. Bioprosthetic valve fracture (BVF) using a high-pressure balloon can be performed to facilitate VIV TAVR. We report data from 20 consecutive clinical cases in which BVF was successfully performed before or after VIV TAVR by inflation of a high-pressure balloon positioned across the valve ring during rapid ventricular pacing. Hemodynamic measurements and calculation of the valve effective orifice area were performed at baseline, immediately after VIV TAVR, and after BVF. BVF was successfully performed in 20 patients undergoing VIV TAVR with balloon-expandable (n=8) or self-expanding (n=12) transcatheter valves in Mitroflow, Carpentier-Edwards Perimount, Magna and Magna Ease, Biocor Epic and Biocor Epic Supra, and Mosaic surgical valves. Successful fracture was noted fluoroscopically when the waist of the balloon released and by a sudden drop in inflation pressure, often accompanied by an audible snap. BVF resulted in a reduction in the mean transvalvular gradient (from 20.5±7.4 to 6.7±3.7 mm Hg, P valve effective orifice area (from 1.0±0.4 to 1.8±0.6 cm 2 , P valves to facilitate VIV TAVR with either balloon-expandable or self-expanding transcatheter valves and results in reduced residual transvalvular gradients and increased valve effective orifice area. © 2017 American Heart Association, Inc.

Diesel engine exhaust particulate filter with intake throttling incineration control

Energy Technology Data Exchange (ETDEWEB)

Ludecke, O.; Rosebrock, T.

1980-07-08

A description is given of a diesel engine exhaust filter and particulate incineration system in combination with a diesel engine having a normally unthrottled air induction system for admitting combustion air to the engine and an exhaust system for carrying off spent combustion products exhausted from the engine, said filter and incineration system comprising: a combustion resistant filter disposed in the exhaust system and operative to collect and retain portions of the largely carbonaceous particulate matter contained in the engine exhaust products, said fiber being capable of withstanding without substantial damage internal temperatures sufficient to burn the collected particulate matter, a throttle in the indication system and operable to restrict air flow into the engine to reduce the admittance of excess combustion air and thereby increase engine exhaust gas temperature, and means to actuate said throttle periodically during engine operation to an air flow restricting burn mode capable of raising the particulates in said filter to their combustion temperature under certain engine operating conditions and to maintain said throttle mode for an interval adequate to burn retained particulates in the filter.

Design and analysis of throttle orifice applying to small space with large pressure drop

International Nuclear Information System (INIS)

Li Yan; Lu Daogang; Zeng Xiaokang

2013-01-01

Throttle orifices are widely used in various pipe systems of nuclear power plants. Improper placement of orifices would aggravate the vibration of the pipe with strong noise, damaging the structure of the pipe and the completeness of the system. In this paper, effects of orifice diameter, thickness, eccentric distance and chamfering on the throttling are analyzed applying CFD software. Based on that, we propose the throttle orifices which apply to small space with large pressure drop are multiple eccentric orifices. The results show that the multiple eccentric orifices can effectively restrain the cavitation and flash distillation, while generating a large pressure drop. (authors)

Influence of throttling of the heavy fraction on the uranium isotope separation in the separation nozzle

International Nuclear Information System (INIS)

Bley, P.; Ehrfeld, W.; Heiden, U.

1978-04-01

In a separation nozzle cascade for enrichment of U-235 the cut of the separation elements is adjusted by throttling the heavy fraction. This control process influences directly the flow properties in the nozzle and may noticeably change its separation characteristics. This paper deals with an experimental investigation of the throttling effect on the separation and control characteristics of the separation nozzle operated with a H 2 /UF 6 mixture. In consideration of the extremely small characteristic dimensions of commercial separation nozzle elements the influence of manufacturing tolerances on the characteristics of the throttled nozzle was analysed in detail. It appears, that the elementary effect of isotope separation increases by throttling of the heavy fraction up to 5% without changing the optimum operating conditions. This increase of the elementary effect is not only obtained for separation nozzles with zero tolerances but also for separation nozzles having finite tolerances of the skimmer position. Tolerances of the nozzle width, however, become increasingly detrimental, when the heavy fraction is throttled. Regarding the control characteristics of the separation nozzle it was found out, that the UF 6 -cut of the throttled nozzle reacts more sensitively to alterations of the operating pressures and less sensitively to alterations of the UF 6 -concentration of the process gas mixture. (orig.) [de

One-shot valve may be remotely actuated

Science.gov (United States)

Kami, S.

1965-01-01

One-shot valve, with spring-loaded plunger and sealing diaphragm, incorporates an emergency release actuated by a remote sensor. The plunger is released by the electrical melting of a fuse link and pierces the valve seal. The valve lowers fluid pressure in a container without losing the contained fluid.

Convex modeling and optimization of a vehicle powertrain equipped with a generator-turbine throttle unit

NARCIS (Netherlands)

Marinkov, S.; Murgovski, N.; de Jager, A.G.

2017-01-01

This paper investigates an internal combustion (gasoline) engine throttled by a generator-turbine unit. Apart from throttling, the purpose of this device is to complement the operation of a conventional car alternator and support its downsizing by introducing an additional source of energy for the

A study on the improvement of the load pressure feedback mechanism of the proportional pressure control valve

International Nuclear Information System (INIS)

Oh, In Ho; Jang, Ji Seong; Lee, Ill Yeong; Chung, Dai Jong; Cho, Sung Hyun

1999-01-01

The proportional pressure control valve having versatile functions and higher performance is an essential component in the open loop controlled rear wheel steering gear of the four wheel steering system on a passenger car. In this study, the authors suggest a new type of load pressure feedback mechanism which can make it easy change the control range of load pressure without changing the capacity of solenoid. The concept of the suggested mechanism, composed of the pressure chamber with throttles in series, was described. The mathematical model was derived from the rear wheel steering gear system consisting of a valve and a cylinder for the purpose of analyzing the valve characteristics. And the programme for computing the characteristic of the valve was developed. Experiments were carried out to confirm the performance of the valve and computations were performed to ascertain the usefulness of the developed programme. The results from the computations fairly coincide with those from the experiments. The results from the experiments and computations show that the performance of new valve is as good as that of the already developed one and the new valve has an advantage in the easiness in varying the control range of load pressure

Closed-loop thrust and pressure profile throttling of a nitrous oxide/hydroxyl-terminated polybutadiene hybrid rocket motor

Science.gov (United States)

Peterson, Zachary W.

Hybrid motors that employ non-toxic, non-explosive components with a liquid oxidizer and a solid hydrocarbon fuel grain have inherently safe operating characteristics. The inherent safety of hybrid rocket motors offers the potential to greatly reduce overall operating costs. Another key advantage of hybrid rocket motors is the potential for in-flight shutdown, restart, and throttle by controlling the pressure drop between the oxidizer tank and the injector. This research designed, developed, and ground tested a closed-loop throttle controller for a hybrid rocket motor using nitrous oxide and hydroxyl-terminated polybutadiene as propellants. The research simultaneously developed closed-loop throttle algorithms and lab scale motor hardware to evaluate the fidelity of the throttle simulations and algorithms. Initial open-loop motor tests were performed to better classify system parameters and to validate motor performance values. Deep-throttle open-loop tests evaluated limits of stable thrust that can be achieved on the test hardware. Open-loop tests demonstrated the ability to throttle the motor to less than 10% of maximum thrust with little reduction in effective specific impulse and acoustical stability. Following the open-loop development, closed-loop, hardware-in-the-loop tests were performed. The closed-loop controller successfully tracked prescribed step and ramp command profiles with a high degree of fidelity. Steady-state accuracy was greatly improved over uncontrolled thrust.

Regulator of the lowering velocity of well pipe string for hydraulic drilling unit

Energy Technology Data Exchange (ETDEWEB)

Umanchik, N P; Bogomazov, B N; Rozin, M M; Yermolayev, V N; Zakharov, A P

1981-01-01

A device is proposed for controlling a hydraulic lifter which includes a throttling valve, two servocylinders with pistons and profile feeler mechanism. In order to improve reliability of automatic lowering of the well pipe string according to the assigned law and to simplify the design, the throttle valve is made in the form of a cylinder with openings and slide valve. The device is equipped with an end switch and a float located on the outer surface of the cylinder. The lower cavity of the throttling valve by means of the pipeline with valve is connected to the cavity of the servocylinder, while the float is installed with possibility of interacting with the end switch which is connected to the pipeline valve.

Control valves for critical applications in refineries; Stellventile bei kritischen Prozessbedingungen in Raffinerien

Energy Technology Data Exchange (ETDEWEB)

Kiesbauer, J. [Samson AG, Frankfurt am Main (Germany)

2001-09-01

In refineries, the process media flowing through valves are primarily liquids. With liquids, critical operating conditions caused by cavitation or flashing may occur. Symptoms are, for instance, increased noise emission, erosion of valve and pipe components or low-frequency mechanical vibration in the valve and the connected pipeline. Under these conditions, in particular, neglecting details can result in negative influences on the plant performance and the costs of ownership. Unfortunately, it is a common practice nowadays to select control valves in a ''quick and dirty'' fashion, because the phases of planning, bidding and order processing are connected with significant pressures of cost and time. This article presents the basic principles underlying the above problems and shows how to eliminate them based on practical examples from refineries. Moreover, a new throttling element is introduced, which is especially suited to the reduction of noise emission produced by cavitation. This new throttling element is implemented in refineries with increasing success. (orig.) [German] In Raffinerien werden Stellgeraete oft mit Fluessigkeiten durchstroemt. Dadurch koennen sich kritische Betriebszustaende als Folge von Kavitation oder Flashing ergeben. Dies aeussert sich z. B. in erhoehter Schallemission, in Erosion an Ventil- und Rohrleitungsbauteilen oder in niederfrequenten mechanischen Vibrationen im Ventil und der angeschlossenen Rohrleitung. Werden solche Einfluesse nicht von Anfang an richtig erfasst und ernst genommen, dann kann sich dies aeusserst negativ auf die Anlagen- und Prozesszuverlaessigkeit auswirken, verbunden mit deutlich erhoehten ''costs of ownership''. Leider ist es gerade heutzutage ueblich, Stellventile ''quick and dirty'' auszulegen, weil die Phasen der Planung, des Angebots und der Bestellung einem sehr starken Zeit- und Kostendruck unterliegen. Dieser Beitrag stellt die wesentlichen

Effects of groove shape of notch on the flow characteristics of spool valve

International Nuclear Information System (INIS)

Ye, Yi; Yin, Chen-Bo; Li, Xing-Dong; Zhou, Wei-jin; Yuan, Feng-feng

2014-01-01

Highlights: • Flow characteristics of notches are studied using CFD simulation and experiment. • Test data is fitted by least square method to analyze discharge coefficient. • The stable value of discharge coefficient is deduced. • Effects of groove shape on steady flow force and throttling stiffness are performed. • The groove shape has significant effects on the flow characteristics. - Abstract: The grooves of notches of hydraulic spool valves are usually designed into various shapes for their desired flow characteristics. The aim of this paper is to clarify the effects of the groove shape on the flow characteristics through computational fluid dynamics (CFD) and experimental investigations. The RNG k–ε turbulence model is used to simulate the pressure distributions of the flow fields inside three notches with their corresponding typical structural grooves in order to analyze the changes of restricted locations along with the openings and, furthermore, to calculate the flow areas of the notches. The accuracy of the employed model is demonstrated by comparing the computational results with the experimental data. Additionally, the flow rate vs. pressure drop data obtained from the experiment is fitted by least square method. On this basis, the discharge coefficient as a function of groove geometry, flow condition, fitting coefficients and its stable value is deduced, proving to be quite consistent with the experimental result. Thanks to the jet flow angles estimated by CFD simulation, the steady flow forces are calculated, which show good agreement with the experimental results except for some small differences. Finally, the throttling stiffness of the three notches is investigated, with that of divergent U-shape groove falls between spheroid-shape groove and triangle-shape groove. Similar results are found for steady flow force. The results indicate that the groove shape has significant effects on the flow characteristics (flow area, discharge

Effect of throttling on burnout heat flux and hydrodynamic instability in natural circulation

International Nuclear Information System (INIS)

Mahmoud, S.I.

1980-01-01

Twenty-four experiments were carried out to study the effect of restriction of the flow before inlet of the test section on burnout heat flux and instability of the flow boiling. These experiments were carried out on a 10, 12, 14, 16 mm out diameter stainless steel heated elements, 50 and 75 cms long centered inside a 26 mm inner diameter stainless steel channel forming an annulus through which water followed upwards to give diameter ratios 2.6, 2.17, 1.86 and 1.63 respectively. The parameters are chosen to cover the lack of the literatures for burnout conditions at low pressures, 1.5, 3, 6, 10 atma). These are of great benefit to the designers of high heat flux devices such as boilers and nuclear reactors ...etc. A detail description of the experimental loop is given. Test section, steam separator, condenser, precooler, preheater, throttle valve, flow measurements and safety devices are designed and constructed for an operating pressure up to 10 atma and temperature up to 220 0 C. The results show that 1. The burnout heat flux first increases and then decreases as the restriction of the flow increases; 2. The hydrodynamic instability increases as the restriction of the flow before the test section increases. (author)

The Evolution of Utilizing Manual Throttles to Avoid Excessively Low LH2 NPSP at the SSME Inlet

Science.gov (United States)

Henfling, Rick

2011-01-01

In the late 1970s, years before the Space Shuttle flew its maiden voyage, it was understood low liquid hydrogen (LH2) Net Positive Suction Pressure (NPSP) at the inlet to the Space Shuttle Main Engine (SSME) could have adverse effects on engine operation. A number of failures within both the External Tank (ET) and the Orbiter Main Propulsion System (MPS) could result in a low LH2 NPSP condition, which at extremely low levels can result in cavitation of SSME turbomachinery. Operational workarounds were developed to take advantage of the onboard crew s ability to manually throttle down the SSMEs (via the Pilot s Speedbrake/Throttle Controller), which alleviated the low LH2 NPSP condition. Manually throttling the SSME to a lower power level resulted in an increase in NPSP, mainly due to the reduction in frictional flow losses while at the lower throttle setting. Early in the Space Shuttle Program s history, the relevant Flight Rule for the Booster flight controllers in Mission Control did not distinguish between ET and Orbiter MPS failures and the same crew action was taken for both. However, after a review of all Booster operational techniques following the Challenger disaster in the late 1980s, it was determined manually throttling the SSME to a lower power was only effective for Orbiter MPS failures and the Flight Rule was updated to reflect this change. The Flight Rule and associated crew actions initially called for a single throttle step to minimum power level when a low threshold for NPSP was met. As engineers refined their understanding of the NPSP requirements for the SSME (through a robust testing program), the operational techniques evolved to take advantage of the additional capabilities. This paper will examine the evolution of the Flight rule and associated procedure and how increases in knowledge about the SSME and the Space Shuttle vehicle as a whole have helped shape their development. What once was a single throttle step when NPSP decreased to a

The Evolution of Utilizing Manual Throttling to Avoid Excessively Low LH2 NPSP at the SSME Inlet

Science.gov (United States)

Henfling, Rick

2010-01-01

In the late 1970s, years before the Space Shuttle flew its maiden voyage, it was understood low liquid hydrogen (LH2) Net Positive Suction Pressure (NPSP) at the inlet to the Space Shuttle Main Engine (SSME) could have adverse effects on engine operation. A number of failures within both the External Tank (ET) and the Orbiter Main Propulsion System (MPS) could result in a low LH2 NPSP condition, which at extremely low levels can result in cavitation of SSME turbomachinery. Operational workarounds were developed to take advantage of the onboard crew s ability to manually throttle down the SSMEs (via the Pilot s Speedbrake/Throttle Controller), which alleviated the low LH2 NPSP condition. Manually throttling the SSME to a lower power level resulted in an increase in NPSP, mainly due to the reduction in frictional flow losses while at the lower throttle setting. Early in the Space Shuttle Program s history, the relevant Flight Rule for the Booster flight controller in Mission Control did not distinguish between ET and Orbiter MPS failures and the same crew action was taken for both. However, after a review of all Booster operational techniques following the Challenger disaster in the late 1980s, it was determined manually throttling the SSME to a lower power was only effective for Orbiter MPS failures and the Flight Rule was updated to reflect this change. The Flight Rule and associated crew actions initially called for a single throttle step to minimum power level when a low threshold for NPSP was met. As engineers refined their understanding of the NPSP requirements for the SSME (through a robust testing program), the operational techniques evolved to take advantage of the additional capabilities. This paper will examine the evolution of the Flight rule and associated procedure and how increases in knowledge about the SSME and the Space Shuttle vehicle as a whole have helped shape their development. What once was a single throttle step when NPSP decreased to a

Manual Throttles-Only Control Effectivity for Emergency Flight Control of Transport Aircraft

Science.gov (United States)

Stevens, Richard; Burcham, Frank W., Jr.

2009-01-01

If normal aircraft flight controls are lost, emergency flight control may be attempted using only the thrust of engines. Collective thrust is used to control flightpath, and differential thrust is used to control bank angle. One issue is whether a total loss of hydraulics (TLOH) leaves an airplane in a recoverable condition. Recoverability is a function of airspeed, altitude, flight phase, and configuration. If the airplane can be recovered, flight test and simulation results on several transport-class airplanes have shown that throttles-only control (TOC) is usually adequate to maintain up-and-away flight, but executing a safe landing is very difficult. There are favorable aircraft configurations, and also techniques that will improve recoverability and control and increase the chances of a survivable landing. The DHS and NASA have recently conducted a flight and simulator study to determine the effectivity of manual throttles-only control as a way to recover and safely land a range of transport airplanes. This paper discusses TLOH recoverability as a function of conditions, and TOC landability results for a range of transport airplanes, and some key techniques for flying with throttles and making a survivable landing. Airplanes evaluated include the B-747, B-767, B-777, B-757, A320, and B-737 airplanes.

Packaged Au-PPy valves for drug delivery systems

Science.gov (United States)

Tsai, Han-Kuan A.; Ma, Kuo-Sheng; Zoval, Jim; Kulinsky, Lawrence; Madou, Marc

2006-03-01

The most common methods for the drug delivery are swallowing pills or receiving injections. However, formulations that control the rate and period of medicine (i.e., time-release medications) are still problematic. The proposed implantable devices which include batteries, sensors, telemetry, valves, and drug storage reservoirs provide an alternative method for the responsive drug delivery system [1]. Using this device, drug concentration can be precisely controlled which enhances drug efficiency and decreases the side effects. In order to achieve responsive drug delivery, a reliable release valve has to be developed. Biocompatibility, low energy consumption, and minimized leakage are the main requirements for such release method. A bilayer structure composed of Au/PPy film is fabricated as a flap to control the release valve. Optimized potentiostatic control to synthesize polypyrrole (PPy) is presented. The release of miniaturize valve is tested and showed in this paper. A novel idea to simultaneously fabricate the device reservoirs as well as protective packaging is proposed in this paper. The solution of PDMS permeability problem is also mentioned in this article.

Waste energy driven air conditioning system (WEDACS)

NARCIS (Netherlands)

Eichhorn, R.H.L.; Boot, M.D.; Luijten, C.C.M.

2009-01-01

In the port injected Spark Ignition (SI) engine, the single greatest part load efficiency reducing factor are energy losses over the throttle valve. The need for this throttle valve arises from the fact that engine power is controlled by the amount of air in the cylinders, since combustion occurs

Valve assembly having remotely replaceable bearings

International Nuclear Information System (INIS)

Johnson, E.R.; Tanner, D.E.

1980-01-01

A valve assembly having remotely replaceable bearings is disclosed wherein a valve disc is supported within a flow duct for rotation about a pair of axially aligned bearings, one of which is carried by a spindle received within a diametral bore in the valve disc, and the other of which is carried by a bearing support block releasably mounted on the duct circumferentially of an annular collar on the valve disc coaxial with its diametrical bore. The spindle and bearing support block are adapted for remote removal to facilitate servicing or replacement of the valve disc support bearings

Development of Overflow-Prevention Valve with Trigger Mechanism.

Science.gov (United States)

Ishino, Yuji; Mizuno, Takeshi; Takasaki, Masaya

2016-09-01

A new overflow-prevention valve for combustible fluid is developed which uses a trigger mechanism. Loading arms for combustible fluid are used for transferring oil from a tanker to tanks and vice versa. The loading arm has a valve for preventing overflow. Overflow- prevention valves cannot use any electric component to avoid combustion. Therefore, the valve must be constructed only by mechanical parts. The conventional overflow-prevention valve uses fluid and pneumatic forces. It consists of a sensor probe, a cylinder, a main valve for shutting off the fluid and a locking mechanism for holding an open state of the main valve. The proposed overflow-prevention valve uses the pressure due to the height difference between the fluid level of the tank and the sensor probe. However, the force of the cylinder produced by the pressure is too small to release the locking mechanism. Therefore, a trigger mechanism is introduced between the cylinder and the locking mechanism. The trigger mechanism produces sufficient force to release the locking mechanism and close the main valve when the height of fluid exceeds a threshold value. A trigger mechanism is designed and fabricated. The operation necessary for closing the main valve is conformed experimentally.

Liquid metal coolant flow rate regulation

International Nuclear Information System (INIS)

Vitkovskij, I.V.; Glukhikh, V.A.; Kirillov, I.R.; Smirnov, A.M.

1981-01-01

Some aspects of fast reactor and experimental bench operation related to liquid metal flow rate regulation are considered. Requirements to the devices for the flow rate regulation are formulated. A new type of these devices namely magnetohydrodynamic (MHD) throttles is described. Structural peculiarities of MHD throttles of different types are described as well. It is noted that the MHD throttles with a screw channel have the best energy mass indices. On the basis of the comparison of the MHD throttles with mechanical valves it is concluded that the MHD throttles described are useful for regulating the flow rates of any working media. Smoothness and accuracy of the flow rate regulation by the throttles are determined by the electric control circuit and may be practically anyone. The total coefficient of hydraulic losses in the throttle channel in the absence of a magnetic field is ten and more times lesser than in completely open mechanical valve. Electromagnetic time constant of the MHD throttles does not exceed several tenths of a second [ru

The patent-technical investigation of throttling control devices for nuclear reactors

International Nuclear Information System (INIS)

Ionajtis, R.R.; Kolganova, L.I.

1979-01-01

Presented are the results of the analysis of the statistic distribution and dynamics of the parents on throttling control devices (TCD) used in nuclear power plants to regulate the coolant flow in the core and technological channels. 197 foreign patents, given in 1950-75, are studied. To analyze the patents proposed is the TCD classification according to the degree of the change of the flowing part geometry (passing cross section), throttling way, drive type (the way of movable part transfer) and the used medium (coolant), and according to the location. The investigation has shown that the TCD with smoothly or stepply changing flowing part (mainly due to the narrowing of the passing cross section for gaseous or other coolant, not specified) is of great interest for the designers. The most of such devices are supposed to be provided with the drive from the external source and to be placed in the technological channel

Influence of Actively Controlled Heat Release Timing on the Performance and Operational Characteristics of a Rotary Valve, Acoustically Resonant Pulse Combustor

KAUST Repository

Lisanti, Joel; Roberts, William L.

2017-01-01

The influence of heat release timing on the performance and operational characteristics of a rotary valve, acoustically resonant pulse combustor is investigated both experimentally and numerically. Simulation results are obtained by solving the quasi-1D Navier-Stokes equations with forced volumetric heat addition. Experimental efforts modify heat release timing through modulated fuel injection and modification of the fluid dynamic mixing. Results indicate that the heat release timing has a profound effect on the operation and efficiency of the pulse combustor and that this timing can be difficult to control experimentally.

Influence of Actively Controlled Heat Release Timing on the Performance and Operational Characteristics of a Rotary Valve, Acoustically Resonant Pulse Combustor

KAUST Repository

Lisanti, Joel

2017-01-05

The influence of heat release timing on the performance and operational characteristics of a rotary valve, acoustically resonant pulse combustor is investigated both experimentally and numerically. Simulation results are obtained by solving the quasi-1D Navier-Stokes equations with forced volumetric heat addition. Experimental efforts modify heat release timing through modulated fuel injection and modification of the fluid dynamic mixing. Results indicate that the heat release timing has a profound effect on the operation and efficiency of the pulse combustor and that this timing can be difficult to control experimentally.

CECE: Expanding the Envelope of Deep Throttling Technology in Liquid Oxygen/Liquid Hydrogen Rocket Engines for NASA Exploration Missions

Science.gov (United States)

Giuliano, Victor J.; Leonard, Timothy G.; Lyda, Randy T.; Kim, Tony S.

2010-01-01

As one of the first technology development programs awarded by NASA under the Vision for Space Exploration, the Pratt & Whitney Rocketdyne (PWR) Deep Throttling, Common Extensible Cryogenic Engine (CECE) program was selected by NASA in November 2004 to begin technology development and demonstration toward a deep throttling, cryogenic engine supporting ongoing trade studies for NASA s Lunar Lander descent stage. The CECE program leverages the maturity and previous investment of a flight-proven hydrogen/oxygen expander cycle engine, the PWR RL10, to develop and demonstrate an unprecedented combination of reliability, safety, durability, throttlability, and restart capabilities in high-energy, cryogenic, in-space propulsion. The testbed selected for the deep throttling demonstration phases of this program was a minimally modified RL10 engine, allowing for maximum current production engine commonality and extensibility with minimum program cost. Four series of demonstrator engine tests have been successfully completed between April 2006 and April 2010, accumulating 7,436 seconds of hot fire time over 47 separate tests. While the first two test series explored low power combustion (chug) and system instabilities, the third test series investigated and was ultimately successful in demonstrating several mitigating technologies for these instabilities and achieved a stable throttling ratio of 13:1. The fourth test series significantly expanded the engine s operability envelope by successfully demonstrating a closed-loop control system and extensive transient modeling to enable lower power engine starting, faster throttle ramp rates, and mission-specific ignition testing. The final hot fire test demonstrated a chug-free, minimum power level of 5.9%, corresponding to an overall 17.6:1 throttling ratio achieved. In total, these tests have provided an early technology demonstration of an enabling cryogenic propulsion concept with invaluable system-level technology data

Door valve for fuel handling path

International Nuclear Information System (INIS)

Makishima, Katsuhiko.

1969-01-01

A door valve is provided which seals cover gas from a liquid metal cooled reactor without leakage therefrom. A threaded shaft is screwed into a heavy box press which is packed with lead. The shaft is adapted to be rotated by an electric motor or a manually operated wheel which is disposed outside of the door valve. A valve plate is suspended from the box press by four guide wheels mounted thereon. The guide wheels are fitted into inclined guide grooves formed at the valve plate and into grooved formed in the inner wall of a valve casing. A locking ball is provided at each side of the valve plate. In operation the shaft rotates and travels to permit the box press and the valve plate to move into the door valve casing, thus releasing the locking balls. The valve plate does not contact the bottom of the casing. When the box press reaches the home position, the valve plate is carried on the valve opening, and the box press presses the valve plate to increase the tightness. The valve plate does not suffer wear as it does not slide over other parts. (Yamaguchi, T.)

Tandem mirror experiment upgrade (TMX-U) throttle, mechanical design, construction, installation, and alignment

International Nuclear Information System (INIS)

Pedrotti, L.R.; Wong, R.L.

1983-01-01

We will soon add a high-field axisymmetric throttle region to the central cell of the TMX-U. Field amplitude will be adjusted between 2.25 and 6.0 T. This field is produced by adding a high-field solenoid and a cee coil to each end of the central cell. We describe these coils as well as the additions to the restraint structure. We analyzed the stresses within the solenoid using the STANSOL code. In addition, we performed a finite-element structural analysis of the complete magnet set with the SAP4 code. Particular attention was paid to the transition section where the new magnets were added and where the currents in the existing magnets were increased. The peak temperature rise in the throttle coil was calculated to be 41 0 C above ambient

Performance Analysis of a Fluidic Axial Oscillation Tool for Friction Reduction with the Absence of a Throttling Plate

Directory of Open Access Journals (Sweden)

Xinxin Zhang

2017-04-01

Full Text Available An axial oscillation tool is proved to be effective in solving problems associated with high friction and torque in the sliding drilling of a complex well. The fluidic axial oscillation tool, based on an output-fed bistable fluidic oscillator, is a type of axial oscillation tool which has become increasingly popular in recent years. The aim of this paper is to analyze the dynamic flow behavior of a fluidic axial oscillation tool with the absence of a throttling plate in order to evaluate its overall performance. In particular, the differences between the original design with a throttling plate and the current default design are profoundly analyzed, and an improvement is expected to be recorded for the latter. A commercial computational fluid dynamics code, Fluent, was used to predict the pressure drop and oscillation frequency of a fluidic axial oscillation tool. The results of the numerical simulations agree well with corresponding experimental results. A sufficient pressure pulse amplitude with a low pressure drop is desired in this study. Therefore, a relative pulse amplitude of pressure drop and displacement are introduced in our study. A comparison analysis between the two designs with and without a throttling plate indicates that when the supply flow rate is relatively low or higher than a certain value, the fluidic axial oscillation tool with a throttling plate exhibits a better performance; otherwise, the fluidic axial oscillation tool without a throttling plate seems to be a preferred alternative. In most of the operating circumstances in terms of the supply flow rate and pressure drop, the fluidic axial oscillation tool performs better than the original design.

The Evolution of Utilizing Manual Throttles to Avoid Low LH2 NPSP at the SSME Inlet

Science.gov (United States)

Henfling, Rick

2011-01-01

Even before the first flight of the Space Shuttle, it was understood low liquid hydrogen (LH2) Net Positive Suction Pressure (NPSP) at the inlet to the Space Shuttle Main Engine (SSME) can have adverse effects on engine operation. A number of failures within both the External Tank (ET) and the Orbiter Main Propulsion System could result in a low LH2 NPSP condition. Operational workarounds were developed to take advantage of the onboard crew s ability to manually throttle down the SSMEs, which alleviated the low LH2 NPSP condition. A throttling down of the SSME resulted in an increase in NPSP, mainly due to the reduction in frictional flow losses while at a lower throttle setting. As engineers refined their understanding of the NPSP requirements for the SSME (through a robust testing program), the operational techniques evolved to take advantage of these additional capabilities. Currently the procedure, which for early Space Shuttle missions required a Return-to-Launch-Site abort, now would result in a nominal Main Engine Cut Off (MECO) and no loss of mission objectives.

Convective Heat Transfer with and without Film Cooling in High Temperature, Fuel Rich and Lean Environments

Science.gov (United States)

2014-09-01

Figure 3.2: Control panel used in experimental facility the controller throttles a solenoid valve until the desired flow rate is achieved. Finally...test objectives. Namely, quartz windows enabled visual spectrum images or laser diagnostics of reacting film cooling layers. Additionally, a sapphire...rate by a solenoid which throttled a valve restrict the flow appropriately. To measure the flow, the controllers pass the bulk flow through a

Exhaust gas recirculation apparatus for internal combustion engine

Energy Technology Data Exchange (ETDEWEB)

Shigemori, M; Eguchi, N

1975-01-07

An exhaust gas recirculation device to reduce nitrogen oxides emission from internal combustion engines is described. The recirculation is achieved by employing a tube connecting between the exhaust pipe and intake tube. A throttle valve is installed within the exhaust pipe between the muffler and recirculation tube, and regulated by exhaust gas temperature. Whenever the gas temperature is high, the valve closes and increases the gas flow to the intake tube. A temperature sensor is installed within the exhaust pipe and controls a solenoid or magnetic air valve linking to the throttle valve through a relay. The recirculation tube can be cooled by a fan to improve the engine power.

Performance of a Throttle Cycle Refrigerator with Nitrogen-Hydrocarbon and Argon-Hydrocarbon Mixtures

Science.gov (United States)

Venkatarathnam, G.; Senthil Kumar, P.; Srinivasa Murthy, S.

2004-06-01

Throttle cycle refrigerators are a class of vapor compression refrigerators that can provide refrigeration at cryogenic temperatures and operate with refrigerant mixtures. The performance of our prototype refrigerators with nitrogen-hydrocarbon, nitrogen-hydrocarbon-helium and argon-hydrocarbon refrigerant mixtures is presented in this paper.

The Use of Large Valve Overlap in Scavenging a Supercharged Spark-ignition Engine Using Fuel Injection

Science.gov (United States)

Schey, Oscar W; Young, Alfred W

1932-01-01

This investigation was conducted to determine the effect of more complete scavenging on the full throttle power and the fuel consumption of a four-stroke-cycle engine. The NACA single-cylinder universal test engine equipped with both a fuel-injection system and a carburetor was used. The engine was scavenged by using a large valve overlap and maintaining a pressure in the inlet manifold of 2 inches of mercury above atmospheric. The maximum valve overlap used was 112 degrees. Tests were conducted for a range of compression ratios from 5.5 to 8.5. Except for variable speed tests, all tests were conducted at an engine speed of 1,500 r.p.m. The results of the tests show that the clearance volume of an engine can be scavenged by using a large valve overlap and about 2 to 5 inches of mercury pressure difference between the inlet and exhaust valve. With a fuel-injection system when the clearance volume was scavenged, a b.m.e.p. of over 185 pounds per square inch and a fuel consumption of 9.45 pound per brake horsepower per hour were obtained with a 6.5 compression ratio. An increase of approximately 10 pounds per square inch b.m.e.p. was obtained with a fuel-injection system over that with a carburetor.

Preliminary Flight Results of a Fly-by-throttle Emergency Flight Control System on an F-15 Airplane

Science.gov (United States)

Burcham, Frank W., Jr.; Maine, Trindel A.; Fullerton, C. Gordon; Wells, Edward A.

1993-01-01

A multi-engine aircraft, with some or all of the flight control system inoperative, may use engine thrust for control. NASA Dryden has conducted a study of the capability and techniques for this emergency flight control method for the F-15 airplane. With an augmented control system, engine thrust, along with appropriate feedback parameters, is used to control flightpath and bank angle. Extensive simulation studies were followed by flight tests. The principles of throttles only control, the F-15 airplane, the augmented system, and the flight results including actual landings with throttles-only control are discussed.

Turbo-generator control with variable valve actuation

Science.gov (United States)

Vuk, Carl T [Denver, IA

2011-02-22

An internal combustion engine incorporating a turbo-generator and one or more variably activated exhaust valves. The exhaust valves are adapted to variably release exhaust gases from a combustion cylinder during a combustion cycle to an exhaust system. The turbo-generator is adapted to receive exhaust gases from the exhaust system and rotationally harness energy therefrom to produce electrical power. A controller is adapted to command the exhaust valve to variably open in response to a desired output for the turbo-generator.

Exergy analysis of transcritical carbon dioxide refrigeration cycle with an expander

International Nuclear Information System (INIS)

Yang Junlan; Ma Yitai; Li Minxia; Guan Haiqing

2005-01-01

In this paper, a comparative study is performed for the transcritical carbon dioxide refrigeration cycles with a throttling valve and with an expander, based on the first and second laws of thermodynamics. The effects of evaporating temperature and outlet temperature of gas cooler on the optimal heat rejection pressure, the coefficients of performance (COP), the exergy losses, and the exergy efficiencies are investigated. In order to identify the amounts and locations of irreversibility within the two cycles, exergy analysis is employed to study the thermodynamics process in each component. It is found that in the throttling valve cycle, the largest exergy loss occurs in the throttling valve, about 38% of the total cycle irreversibility. In the expander cycle, the irreversibility mainly comes from the gas cooler and the compressor, approximately 38% and 35%, respectively. The COP and exergy efficiency of the expander cycle are on average 33% and 30% higher than those of the throttling valve cycle, respectively. It is also concluded that an optimal heat rejection pressure can be obtained for all the operating conditions to maximize the COP. The analysis results are of significance to provide theoretical basis for optimization design and operation control of the transcritical carbon dioxide cycle with an expander

FEATURES OF CONTROLLING ELECTROPNEUMATIC VALVES OF ACTUATOR TO CONTROL ITS CLUTCH WITH ACCELERATION VALVE

Directory of Open Access Journals (Sweden)

O. A. Yaryta

2018-01-01

Full Text Available The article deals with one of the ways to control an actuator of the automated clutch control system. The aim is to design control of the electropneumatic actuator, to control its coupling with the acceleration valve on the basis of experimental research as well as to provide rational parameters of the automated clutch control system for the robotic transmission. The feature of the system is an acceleration valve in the design of the electropneumatic actuator to control the clutch. New links demand to adjust the way to control the actuator. The connection of Pulse-Width Modulation (PWM with single power supply pulses to control electropneumatic valves is substantiated. The quantitative characteristics of single control pulses and PWM ones are determined. The error of operation accuracy for various ways of the control of the electropneumatic actuator to control the clutch of the robotic transmission is determined. Obtained separate PWM area is designed to suppress the initial hysteresis when the rod of the clutch actuator is moved. An algorithm for the operation of a clutch control system is proposed, taking into account the use of two modes of operation of solenoid valves. A graphical interpretation of the clutch control algorithm is presented, which gives an idea of the location of the constant signal feeding zones to the solenoid valve, as well as the operation areas of the solenoid valve in PWM mode. The control algorithm of the clutch booster provides a mode of guaranteed absence of excess pressure in the pneumatic cylinder after releasing the clutch pedal, provided that two normally closed solenoid valves are used. This configuration of the electro-pneumatic clutch control system allows the use of an emergency clutch release system in case of voltage absence. The reference algorithm for filtering the array of data coming from the feedback sensor, as well as the numerical values of the delay caused by the presence of a filter, are given.

ASIL determination for motorbike’s Electronics Throttle Control System (ETCS) mulfunction

OpenAIRE

Rokhani Fakhrul Zaman; Abdul Rahman Muhammad Taqiuddin; Kamsani Noor Ain; Mohd Sidek Roslina; Saripan M Iqbal; Samsudin Khairulmizam; Hassan Mohd Khair

2017-01-01

Electronics Throttle Control System (ETCS) is the principal electronic unit in all fuel injection engine motorbike, augmenting the engine performance efficiency in comparison to the conventional carburetor based engine. ETCS is regarded as a safety-critical component, whereby ETCS malfunction can cause unintended acceleration or deceleration event, which can be hazardous to riders. In this study, Hazard Analysis and Risk Assessment, an ISO26262 functional safety standard analysis has been app...

Organic flash cycles for efficient power production

Science.gov (United States)

Ho, Tony; Mao, Samuel S.; Greif, Ralph

2016-03-15

This disclosure provides systems, methods, and apparatus related to an Organic Flash Cycle (OFC). In one aspect, a modified OFC system includes a pump, a heat exchanger, a flash evaporator, a high pressure turbine, a throttling valve, a mixer, a low pressure turbine, and a condenser. The heat exchanger is coupled to an outlet of the pump. The flash evaporator is coupled to an outlet of the heat exchanger. The high pressure turbine is coupled to a vapor outlet of the flash evaporator. The throttling valve is coupled to a liquid outlet of the flash evaporator. The mixer is coupled to an outlet of the throttling valve and to an outlet of the high pressure turbine. The low pressure turbine is coupled to an outlet of the mixer. The condenser is coupled to an outlet of the low pressure turbine and to an inlet of the pump.

A prediction method of temperature distribution and thermal stress for the throttle turbine rotor and its application

Directory of Open Access Journals (Sweden)

Yang Yu

2017-01-01

Full Text Available In this paper, a prediction method of the temperature distribution for the thermal stress for the throttle-regulated steam turbine rotor is proposed. The rotor thermal stress curve can be calculated according to the preset power requirement, the operation mode and the predicted critical parameters. The results of the 660 MW throttle turbine rotor show that the operators are able to predict the operation results and to adjust the operation parameters in advance with the help of the inertial element method. Meanwhile, it can also raise the operation level, thus providing the technical guarantee for the thermal stress optimization control and the safety of the steam turbine rotor under the variable load operation.

Preliminary flight test results of a fly-by-throttle emergency flight control system on an F-15 airplane

Science.gov (United States)

Burcham, Frank W., Jr.; Maine, Trindel A.; Fullerton, C. G.; Wells, Edward A.

1993-01-01

A multi-engine aircraft, with some or all of the flight control system inoperative, may use engine thrust for control. NASA Dryden has conducted a study of the capability and techniques for this emergency flight control method for the F-15 airplane. With an augmented control system, engine thrust, along with appropriate feedback parameters, is used to control flightpath and bank angle. Extensive simulation studies have been followed by flight tests. This paper discusses the principles of throttles-only control, the F-15 airplane, the augmented system, and the flight results including landing approaches with throttles-only control to within 10 ft of the ground.

An Experimental Study of Emission and Combustion Characteristics of Marine Diesel Engine in Case of Cylinder Valves Leakage

Directory of Open Access Journals (Sweden)

Kowalski Jerzy

2015-09-01

Full Text Available Presented paper shows the results of the laboratory tests on the relationship between throttling of both air intake duct and exhaust gas duct and a gaseous emission from the marine engine. The object of research is a laboratory, four-stroke, DI diesel engine, operated at loads from 50 kW to 250 kW at a constant speed equal to 750 rpm. During the laboratory tests over 50 parameters of the engine were measured with its technical condition recognized as a „working properly” and with simulated leakage of both air intake valve and exhaust gas valve on the second cylinder. The results of this laboratory research confirm that the leakage of cylinder valves causes no significant changes of the thermodynamic parameters of the engine. Simulated leakages through the inlet and exhaust valve caused a significant increase in fuel consumption of the engine. Valve leakages cause an increase of the exhaust gas temperature behind the cylinder with leakage and behind other cylinders. The exhaust gas temperature increase is relatively small and clearly visible only at low loads of the engine. The increase of the temperature and pressure of the charging air behind the intercooler were observed too. Charging air temperature is significantly higher during the engine operation with inlet valve leakage. The study results show significant increases of the CO, NOx and CO2 emission for all the mentioned malfunctions. The conclusion is that the results of measurements of the composition of the exhaust gas may contain valuable diagnostic information about the technical condition of the air intake duct and the exhaust gas duct of the marine engine.

Bioprosthetic Valve Fracture to Facilitate Transcatheter Valve-in-Valve Implantation.

Science.gov (United States)

Allen, Keith B; Chhatriwalla, Adnan K; Cohen, David J; Saxon, John T; Aggarwal, Sanjeev; Hart, Anthony; Baron, Suzanne; Davis, J Russell; Pak, Alex F; Dvir, Danny; Borkon, A Michael

2017-11-01

Valve-in-valve transcatheter aortic valve replacement is less effective in small surgical bioprostheses. We evaluated the feasibility of bioprosthetic valve fracture with a high-pressure balloon to facilitate valve-in-valve transcatheter aortic valve replacement. In vitro bench testing on aortic tissue valves was performed on 19-mm and 21-mm Mitroflow (Sorin, Milan, Italy), Magna and Magna Ease (Edwards Lifesciences, Irvine, CA), Trifecta and Biocor Epic (St. Jude Medical, Minneapolis, MN), and Hancock II and Mosaic (Medtronic, Minneapolis, MN). High-pressure balloons Tru Dilation, Atlas Gold, and Dorado (C.R. Bard, Murray Hill, NJ) were used to determine which valves could be fractured and at what pressure fracture occurred. Mitroflow, Magna, Magna Ease, Mosaic, and Biocor Epic surgical valves were successfully fractured using high-pressures balloon 1 mm larger than the labeled valve size whereas Trifecta and Hancock II surgical valves could not be fractured. Only the internal valve frame was fractured, and the sewing cuff was never disrupted. Manufacturer's rated burst pressures for balloons were exceeded, with fracture pressures ranging from 8 to 24 atmospheres depending on the surgical valve. Testing further demonstrated that fracture facilitated the expansion of previously constrained, underexpanded transcatheter valves (both balloon and self-expanding) to the manufacturer's recommended size. Bench testing demonstrates that the frame of most, but not all, bioprosthetic surgical aortic valves can be fractured using high-pressure balloons. The safety of bioprosthetic valve fracture to optimize valve-in-valve transcatheter aortic valve replacement in small surgical valves requires further clinical investigation. Copyright © 2017 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

Independent deterministic analysis of the operational event with turbine valve closure and one atmospheric dump valve stuck open

International Nuclear Information System (INIS)

Rijova, N.

2007-01-01

The paper presents the results of the independent analysis of the operational event which took place on 07.11.2003 at Unit 1 of Rostov NPP. The event started with switching off the electrical generator of the turbine due to a short cut at the local switching substation. The turbine isolating valves closed to prevent damage of the turbine. The condenser dump valves (BRU-K) and the atmospheric dump valves (BRU-A) opened to release the vapour generated in the steam generators. After the pressure decrease in the steam generators BRU-K and BRU-A closed but one valve stuck opened. The emergency core cooling system was activated automatically. The main circulation pump of the loop corresponding to the steam generator with the stuck BRU-A was tripped. The stuck valve was closed by the operational stuff manually. No safety limits were violated. The analysis of the event was carried out using ATHLET code. A reasonable agreement was achieved between the calculated and measured values. (author)

Electrically controlled fuel injection device for internal combustion engines with air quantity meter. Elektrisch gesteuerte Kraftstoffeinspritzeinrichtung fuer Brennkraftmaschinen mit Luftmengenmesser

Energy Technology Data Exchange (ETDEWEB)

Kraus, B; Soell, W

1980-12-11

The invention concerns an electrically controlled preferably intermittently working fuel injection device for internal combustion engines with a throttle valve, a solenoid operated injection valve and a transistor circuit, which supplies electrical pulses used to open the injection valve synchronously to the revolution of the crankshaft. The invention is characterized by the fact that an electrical control device is provided, which extends the individual opening pulses in thrust operation (with the throttle valve closed or nearly closed and with a working speed above the speed). The extension produced by the control device decreases from a value at about 20% for the maximum speed to a value of 0 for the tickover speed. Details of the transistor control are made clear by detailed circuit diagrams and 5 patent claims.

International Heart Valve Bank Survey: A Review of Processing Practices and Activity Outcomes

Science.gov (United States)

Albrecht, Helmi; Lim, Yeong Phang; Manning, Linda

2013-01-01

A survey of 24 international heart valve banks was conducted to acquire information on heart valve processing techniques used and outcomes achieved. The objective was to provide an overview of heart valve banking activities for tissue bankers, tissue banking associations, and regulatory bodies worldwide. Despite similarities found for basic manufacturing processes, distinct differences in procedural details were also identified. The similarities included (1) use of sterile culture media for procedures, (2) antibiotic decontamination, (3) use of dimethyl sulfoxide (DMSO) as a cryoprotectant, (4) controlled rate freezing for cryopreservation, and (5) storage at ultralow temperatures of below −135°C. Differences in procedures included (1) type of sterile media used, (2) antibiotics combination, (3) temperature and duration used for bioburden reduction, (4) concentration of DMSO used for cryopreservation, and (5) storage duration for released allografts. For most banks, the primary reasons why allografts failed to meet release criteria were positive microbiological culture and abnormal morphology. On average, 85% of allografts meeting release criteria were implanted, with valve size and type being the main reasons why released allografts were not used clinically. The wide variation in percentage of allografts meeting release requirements, despite undergoing validated manufacturing procedures, justifies the need for regular review of important outcomes as cited in this paper, in order to encourage comparison and improvements in the HVBs' processes. PMID:24163756

ASIL determination for motorbike's Electronics Throttle Control System (ETCS) mulfunction

Science.gov (United States)

Zaman Rokhani, Fakhrul; Rahman, Muhammad Taqiuddin Abdul; Ain Kamsani, Noor; Sidek, Roslina Mohd; Saripan, M. Iqbal; Samsudin, Khairulmizam; Khair Hassan, Mohd

2017-11-01

Electronics Throttle Control System (ETCS) is the principal electronic unit in all fuel injection engine motorbike, augmenting the engine performance efficiency in comparison to the conventional carburetor based engine. ETCS is regarded as a safety-critical component, whereby ETCS malfunction can cause unintended acceleration or deceleration event, which can be hazardous to riders. In this study, Hazard Analysis and Risk Assessment, an ISO26262 functional safety standard analysis has been applied on motorbike's ETCS to determine the required automotive safety integrity level. Based on the analysis, the established automotive safety integrity level can help to derive technical and functional safety measures for ETCS development.

Engineering stategies and implications of using higher plants for throttling gas and water exchange in a controlled ecological life support system

Science.gov (United States)

Chamberland, Dennis; Wheeler, Raymond M.; Corey, Kenneth A.

1993-01-01

Engineering stategies for advanced life support systems to be used on Lunar and Mars bases involve a wide spectrum of approaches. These range from purely physical-chemical life support strategies to purely biological approaches. Within the context of biological based systems, a bioengineered system can be devised that would utilize the metabolic mechanisms of plants to control the rates of CO2 uptake and O2 evolution (photosynthesis) and water production (transpiration). Such a mechanism of external engineering control has become known as throttling. Research conducted at the John F. Kennedy Space Center's Controlled Ecological Life Support System Breadboard Project has demonstrated the potential of throttling these fluxes by changing environmental parameters affecting the plant processes. Among the more effective environmental throttles are: light and CO2 concentration for controllingthe rate of photsynthesis and humidity and CO2 concentration for controlling transpiration. Such a bioengineered strategy implies control mechanisms that in the past have not been widely attributed to life support systems involving biological components and suggests a broad range of applications in advanced life support system design.

Theoretical and Experimental Studies of a Switched Inertance Hydraulic System in a Four-Port High-Speed Switching Valve Configuration

Directory of Open Access Journals (Sweden)

Min Pan

2017-06-01

Full Text Available The switched inertance hydraulic system (SIHS is a novel high-bandwidth and energy-efficient digital device which can adjust or control flow and pressure by a means that does not rely on throttling the flow and dissipation of power. An SIHS can provide an efficient step-up or step-down of pressure or flow rate by using a digital control signal. In this article, analytical models of an SIHS in a four-port high-speed switching valve configuration are proposed, and the system dynamics and performance are investigated theoretically and experimentally. The flow responses, system characteristics, and power consumption can be predicted effectively and accurately by using the proposed models, which were validated by comparing with experiments and with numerical simulation. The four-port configuration is compared with the three-port configuration, and it is concluded that the former one is less efficient for valves of the same size, but provides a bi-direction control capability. As bi-direction control is a common requirement, this constitutes an important contribution to the development of efficient digital hydraulics.

Combustion mode switching with a turbocharged/supercharged engine

Science.gov (United States)

Mond, Alan; Jiang, Li

2015-09-22

A method for switching between low- and high-dilution combustion modes in an internal combustion engine having an intake passage with an exhaust-driven turbocharger, a crankshaft-driven positive displacement supercharger downstream of the turbocharger and having variable boost controllable with a supercharger bypass valve, and a throttle valve downstream of the supercharger. The current combustion mode and mass air flow are determined. A switch to the target combustion mode is commanded when an operating condition falls within a range of predetermined operating conditions. A target mass air flow to achieve a target air-fuel ratio corresponding to the current operating condition and the target combustion mode is determined. The degree of opening of the supercharger bypass valve and the throttle valve are controlled to achieve the target mass air flow. The amount of residual exhaust gas is manipulated.

Autonomous valve for detection of biopolymer degradation

DEFF Research Database (Denmark)

Keller, Stephan Urs; Noeth, Nadine-Nicole; Fetz, Stefanie

2009-01-01

We present a polymer microvalve that allows the detection of biopolymer degradation without the need of external energy. The valve is based on a polymer container filled with a colored marker solution and closed by a thin lid. This structure is covered by a film of poly(L-lactide) and degradation...... of the biopolymer triggers the release of the color which is detected visually. The autonomous valve has potential for the fast testing of biopolymer degradation under various environmental conditions or by specific enzymes....

Evaluation of steady flow torques and pressure losses in a rotary flow control valve by means of computational fluid dynamics

International Nuclear Information System (INIS)

Okhotnikov, Ivan; Noroozi, Siamak; Sewell, Philip; Godfrey, Philip

2017-01-01

Highlights: • A novel design of a rotary flow control valve driven by a stepper motor is proposed. • The intended use of the valve in the high flow rate independent metering hydraulic system is suggested. • Pressure drops, steady flow torques of the valve for various flow rates and orifice openings are studied by means of computational fluid dynamics. • The discharge coefficient and flow jet angles dependencies on the orifice opening are obtained. • A design method to decrease the flow forces without reducing the flow rate in single-staged valves is demonstrated. - Abstract: In this paper, a novel design of a rotary hydraulic flow control valve has been presented for high flow rate fluid power systems. High flow rates in these systems account for substantial flow forces acting on the throttling elements of the valves and cause the application of mechanically sophisticated multi-staged servo valves for flow regulation. The suggested design enables utilisation of single-stage valves in power hydraulics operating at high flow rates regimes. A spool driver and auxiliary mechanisms of the proposed valve design were discussed and selection criteria were suggested. Analytical expressions for metering characteristics as well as steady flow torques have been derived. Computational fluid dynamics (CFD) analysis of steady state flow regimes was conducted to evaluate the hydraulic behaviour of the proposed valve. This study represents a special case of an independent metering concept applied to the design of power hydraulic systems with direct proportional valve control operating at flow rates above 150 litres per minute. The result gained using parametric CFD simulations predicted the induced torque and the pressure drops due to a steady flow. Magnitudes of these values prove that by minimising the number of spool's mobile metering surfaces it is possible to reduce the flow-generated forces in the new generation of hydraulic valves proposed in this study

Modelling and multi-objective optimization of a variable valve-timing spark-ignition engine using polynomial neural networks and evolutionary algorithms

International Nuclear Information System (INIS)

Atashkari, K.; Nariman-Zadeh, N.; Goelcue, M.; Khalkhali, A.; Jamali, A.

2007-01-01

The main reason for the efficiency decrease at part load conditions for four-stroke spark-ignition (SI) engines is the flow restriction at the cross-sectional area of the intake system. Traditionally, valve-timing has been designed to optimize operation at high engine-speed and wide open throttle conditions. Several investigations have demonstrated that improvements at part load conditions in engine performance can be accomplished if the valve-timing is variable. Controlling valve-timing can be used to improve the torque and power curve as well as to reduce fuel consumption and emissions. In this paper, a group method of data handling (GMDH) type neural network and evolutionary algorithms (EAs) are firstly used for modelling the effects of intake valve-timing (V t ) and engine speed (N) of a spark-ignition engine on both developed engine torque (T) and fuel consumption (Fc) using some experimentally obtained training and test data. Using such obtained polynomial neural network models, a multi-objective EA (non-dominated sorting genetic algorithm, NSGA-II) with a new diversity preserving mechanism are secondly used for Pareto based optimization of the variable valve-timing engine considering two conflicting objectives such as torque (T) and fuel consumption (Fc). The comparison results demonstrate the superiority of the GMDH type models over feedforward neural network models in terms of the statistical measures in the training data, testing data and the number of hidden neurons. Further, it is shown that some interesting and important relationships, as useful optimal design principles, involved in the performance of the variable valve-timing four-stroke spark-ignition engine can be discovered by the Pareto based multi-objective optimization of the polynomial models. Such important optimal principles would not have been obtained without the use of both the GMDH type neural network modelling and the multi-objective Pareto optimization approach

Practical use of valve seating machine with remote control system for main steam isolation valve at N.P.S

International Nuclear Information System (INIS)

Ito, Sadao; Noda, Hiroshi; Sadamura, Morito; Utsunomiya, Yasushi.

1975-01-01

The main steam isolation valves in BWR power stations are installed at the boundary of reactor containment vessels, and 2 valves in each main steam system total 8 valves in a plant. They are pneumatically operated Y type globe valves for preventing the release of radioactive substances in the atmosphere in case of the breaking of main steam pipes and also preventing the loss of coolant in case of the breaking of recirculating equipments. Therefore careful leak test, inspection, and seat-fitting are carried out to the valves at each regular maintenance. The manual maintenance work is difficult because of narrow space and the reduction of exposure, and the seat-fitting work requires the skill of high degree, therefore Okano Valve Manufacturing Co. and Tokyo Electric Power Co. jointly started the research and development of an automatic valve seating machine, and successfully put it to practical use in Fukushima No.1 Nuclear Power Station in Nov. 1974. First, the problems in the manual seat-fitting work were investigated, and the means to mechanically solve them were materialized with a prototype machine. After its mock-up test, an actual machine was designed and manufactured. The test result showed remarkable reduction of exposure and labor-saving, and the leak evaluation was sufficiently below the allowable value. (Kako, I.)

Effect and limitation of tuning accelerator pedal sensitivity by DBW; DBW ni yoru akuseru kando settei no koka to genkai

Energy Technology Data Exchange (ETDEWEB)

Takada, Y; Morita, S [Osaka City University, Osaka (Japan)

1997-10-01

DBW (Drive By Wire) system makes the constraint of direct connection between an accelerator pedal and the throttle valve free, so that optionally turning of throttle valve sensitivity becomes possible in automobiles driving. Reported here is the discussion of the effect and the limitation of this optionally tuning. As the former result, it became clear that the tuning method using torque signal and speed signal of the drive shaft, was easier than the method using only speed signal by PD control action. And as the latter result, upper limit was bound by the low gear ratio and tire spin. 2 refs., 11 figs.

Fiber heart valve prosthesis: influence of the fabric construction parameters on the valve fatigue performances.

Science.gov (United States)

Vaesken, Antoine; Heim, Frederic; Chakfe, Nabil

2014-12-01

Transcatheter aortic valve replacement (TAVR) has become today a largely considered alternative technique to surgical valve replacement in patients who are not operable or patients with high risk for open chest surgery. However, the biological valve tissue used in the devices implanted clinically appears to be fragile material when folded for low diameter catheter insertion purpose and released in calcified environment with irregular geometry. Textile polyester material is characterized by outstanding folding and strength properties combined with proven biocompatibility. It could thereof be considered to replace biological valve leaflets in the TAVR procedure. The textile construction parameters must however be tuned to obtain a material compatible with the valve requested durability. In that context, one issue to be addressed is the friction effect that occurs between filaments and between yarns within a fabric under flexure loading. This phenomenon could be critical for the resistance of the material on the long term. The purpose of the present work is to assess the fatigue performances of textile valve prototypes made from different fabric constructions (monofilament, multifilament, calendered mutifilament) under accelerated cyclic loading. The goal is to identify, which construction is the best suited to long term fatigue stress. Results show that calendered multifilament and monofilament fabric constructions undergo strong ruptures already from 40 Mio cycles, while non calendered multifilament appears more durable. The rupture patterns observed point out that durability is directly related to the flexure stiffness level of the fibrous elements in the construction. Copyright © 2014 Elsevier Ltd. All rights reserved.

Using Time-Driven Activity-Based Costing as a Key Component of the Value Platform: A Pilot Analysis of Colonoscopy, Aortic Valve Replacement and Carpal Tunnel Release Procedures.

Science.gov (United States)

Martin, Jacob A; Mayhew, Christopher R; Morris, Amanda J; Bader, Angela M; Tsai, Mitchell H; Urman, Richard D

2018-04-01

Time-driven activity-based costing (TDABC) is a methodology that calculates the costs of healthcare resources consumed as a patient moves along a care process. Limited data exist on the application of TDABC from the perspective of an anesthesia provider. We describe the use of TDABC, a bottom-up costing strategy and financial outcomes for three different medical-surgical procedures. In each case, a multi-disciplinary team created process maps describing the care delivery cycle for a patient encounter using the TDABC methodology. Each step in a process map delineated an activity required for delivery of patient care. The resources (personnel, equipment and supplies) associated with each step were identified. A per minute cost for each resource expended was generated, known as the capacity cost rate, and multiplied by its time requirement. The total cost for an episode of care was obtained by adding the cost of each individual resource consumed as the patient moved along a clinical pathway. We built process maps for colonoscopy in the gastroenterology suite, calculated costs of an aortic valve replacement by comparing surgical aortic valve replacement (SAVR) versus transcatheter aortic valve replacement (TAVR) techniques, and determined the cost of carpal tunnel release in an operating room versus an ambulatory procedure room. TDABC is central to the value-based healthcare platform. Application of TDABC provides a framework to identify process improvements for health care delivery. The first case demonstrates cost-savings and improved wait times by shifting some of the colonoscopies scheduled with an anesthesiologist from the main hospital to the ambulatory facility. In the second case, we show that the deployment of an aortic valve via the transcatheter route front loads the costs compared to traditional, surgical replacement. The last case demonstrates significant cost savings to the healthcare system associated with re-organization of staff required to execute a

Selected Aircraft Throttle Controller With Support Of Fuzzy Expert Inference System

Directory of Open Access Journals (Sweden)

Żurek Józef

2014-12-01

Full Text Available The paper describes Zlin 143Lsi aircraft engine work parameters control support method – hourly fuel flow as a main factor under consideration. The method concerns project of aircraft throttle control support system with use of fuzzy logic (fuzzy inference. The primary purpose of the system is aircraft performance optimization, reducing flight cost at the same time and support proper aircraft engine maintenance. Matlab Software and Fuzzy Logic Toolbox were used in the project. Work of the system is presented with use of twenty test samples, five of them are presented graphically. In addition, system control surface, included in the paper, supports system all work range analysis.

Investigation of New Servo Drive Concept Utilizing Two Fixed Displacement Units

DEFF Research Database (Denmark)

Pedersen, Henrik C.; Schmidt, Lasse; Andersen, Torben Ole

2014-01-01

Traditional valve controlled hydraulic drives have an inherent power loss, due to the throttling over the valves, which limits the maximum system efficiency. Pump controlled direct drives do not have this inherent limitation, but are limited when it comes to controlling asymmetric cylinders, why...

Investigation of New Servo Drive Concept Utilizing Two Fixed Displacement Units

DEFF Research Database (Denmark)

Pedersen, Henrik Clemmensen; Schmidt, Lasse; Andersen, Torben O.

2015-01-01

Traditional valve controlled hydraulic drives have an inherent power loss, due to the throttling over the valves, which limits the maximum system efficiency. Pump controlled direct drives do not have this inherent limitation, but are limited when it comes to controlling asymmetric cylinders, why...

Logic Model Checking of Unintended Acceleration Claims in the 2005 Toyota Camry Electronic Throttle Control System

Science.gov (United States)

Gamble, Ed; Holzmann, Gerard

2011-01-01

Part of the US DOT investigation of Toyota SUA involved analysis of the throttle control software. JPL LaRS applied several techniques, including static analysis and logic model checking, to the software. A handful of logic models were built. Some weaknesses were identified; however, no cause for SUA was found. The full NASA report includes numerous other analyses

Development of magnetic drive packless valves for commercial purpose

International Nuclear Information System (INIS)

Hwang, Sung Tai; Choi, J. H.; Jeong, K. C.; Jeong, J. Y.; Choi, Y. D.; Kwon, S. W.; Kim, B. H.

1997-01-01

A study on development of magnetic drive packless valves for commercial purpose showed the results as follows: 1) characteristics and principle of the valve 2) study on the radial rays effecting to the permanent magnets 3) effects of temperature on the magnetic driving device a) temperature-dependency of the Nd-casting magnets b) effects of temperature on the heat releasing fins of high-temperature valve 4) optimization of torque a) arranging method of permanent magnets b) measuring method and results of torque 5) enlargement of magnetic rotating force a) experiments for the torque enlargement 6) calculation and pressure test for the pressure-resisting structure of magnetic power transmitting device a) calculation for the flat circular plates under pressure b) pressure test of the separating plate 7) design and manufacture of the valve 8) patent application. (author). 1 ref., 18 tabs., 38 figs

A theoretical model for measuring mass flowrate and quality of two phase flow by the noise of throttling set

International Nuclear Information System (INIS)

Tong Yunxian; Wang Wenran

1992-03-01

The mass flowrate and steam quality measuring of two phase flowrate is an essential issue in the tests of loss-of-coolant accident (LOCA). The spatial stochastic distribution of phase concentration would cause a differential pressure noise when two phase flow is crossing a throttling set. Under the assumption of that the variance of disperse phase concentration is proportional to its mean phase concentration and by using the separated flow model of two phase flow, it has demonstrated that the variance of noise of differential pressure square root is approximately proportional to the flowrate of disperse phase. Thus, a theoretical model for measuring mass flowrate and quality of two phase flow by noise measurement is developed. It indicates that there is a possibility to measure two phase flowrate and steam quality by using the simple theoretical model and a single throttling set

A microfluidic timer for timed valving and pumping in centrifugal microfluidics.

Science.gov (United States)

Schwemmer, F; Zehnle, S; Mark, D; von Stetten, F; Zengerle, R; Paust, N

2015-03-21

Accurate timing of microfluidic operations is essential for the automation of complex laboratory workflows, in particular for the supply of sample and reagents. Here we present a new unit operation for timed valving and pumping in centrifugal microfluidics. It is based on temporary storage of pneumatic energy and time delayed sudden release of said energy. The timer is loaded at a relatively higher spinning frequency. The countdown is started by reducing to a relatively lower release frequency, at which the timer is released after a pre-defined delay time. We demonstrate timing for 1) the sequential release of 4 liquids at times of 2.7 s ± 0.2 s, 14.0 s ± 0.5 s, 43.4 s ± 1.0 s and 133.8 s ± 2.3 s, 2) timed valving of typical assay reagents (contact angles 36-78°, viscosities 0.9-5.6 mPa s) and 3) on demand valving of liquids from 4 inlet chambers in any user defined sequence controlled by the spinning protocol. The microfluidic timer is compatible to all wetting properties and viscosities of common assay reagents and does neither require assistive equipment, nor coatings. It can be monolithically integrated into a microfluidic test carrier and is compatible to scalable fabrication technologies such as thermoforming or injection molding.

SQERTSS: Dynamic rank based throttling of transition probabilities in kinetic Monte Carlo simulations

International Nuclear Information System (INIS)

Danielson, Thomas; Sutton, Jonathan E.; Hin, Céline; Virginia Polytechnic Institute and State University; Savara, Aditya

2017-01-01

Lattice based Kinetic Monte Carlo (KMC) simulations offer a powerful simulation technique for investigating large reaction networks while retaining spatial configuration information, unlike ordinary differential equations. However, large chemical reaction networks can contain reaction processes with rates spanning multiple orders of magnitude. This can lead to the problem of “KMC stiffness” (similar to stiffness in differential equations), where the computational expense has the potential to be overwhelmed by very short time-steps during KMC simulations, with the simulation spending an inordinate amount of KMC steps / cpu-time simulating fast frivolous processes (FFPs) without progressing the system (reaction network). In order to achieve simulation times that are experimentally relevant or desired for predictions, a dynamic throttling algorithm involving separation of the processes into speed-ranks based on event frequencies has been designed and implemented with the intent of decreasing the probability of FFP events, and increasing the probability of slow process events -- allowing rate limiting events to become more likely to be observed in KMC simulations. This Staggered Quasi-Equilibrium Rank-based Throttling for Steady-state (SQERTSS) algorithm designed for use in achieving and simulating steady-state conditions in KMC simulations. Lastly, as shown in this work, the SQERTSS algorithm also works for transient conditions: the correct configuration space and final state will still be achieved if the required assumptions are not violated, with the caveat that the sizes of the time-steps may be distorted during the transient period.

The effect of valve strategy on in-cylinder flow and combustion

Energy Technology Data Exchange (ETDEWEB)

Soederberg, F

1997-01-01

This paper examines the effects of different valve strategies and their effect on in-cylinder flow and combustion. A conventional four valve per cylinder otto engine was modified to enable optical access. The flow measurements were made with a two-component laser Doppler velocimetry system. The combustion was monitored by running pressure data from a pressure transducer through a one-zone heat release model. The results show that when the valves operate normally a barrel flow is present and when one valve is closed a swirling flow occurs. No increase in turbulence was found with later phasing, except in the case of very late inlet valve opening and port deactivation. This resulted in a jet with high turbulence, making the combustion fast and stable, even with a very lean mixture ({lambda}=1.8). 6 refs, 44 figs, 4 tabs

Fracturing mechanics before valve-in-valve therapy of small aortic bioprosthetic heart valves.

Science.gov (United States)

Johansen, Peter; Engholt, Henrik; Tang, Mariann; Nybo, Rasmus F; Rasmussen, Per D; Nielsen-Kudsk, Jens Erik

2017-10-13

Patients with degraded bioprosthetic heart valves (BHV) who are not candidates for valve replacement may benefit from transcatheter valve-in-valve (VIV) therapy. However, in smaller-sized surgical BHV the resultant orifice may become too narrow. To overcome this, the valve frame can be fractured by a high-pressure balloon prior to VIV. However, knowledge on fracture pressures and mechanics are prerequisites. The aim of this study was to identify the fracture pressures needed in BHV, and to describe the fracture mechanics. Commonly used BHV of small sizes were mounted on a high-pressure balloon situated in a biplane fluoroscopic system with a high-speed camera. The instant of fracture was captured along with the balloon pressure. The valves were inspected for material protrusion and later dissected for fracture zone investigation and description. The valves with a polymer frame fractured at a lower pressure (8-10 atm) than those with a metal stent (19-26 atm). None of the fractured valves had elements protruding. VIV procedures in small-sized BHV may be performed after prior fracture of the valve frame by high-pressure balloon dilatation. This study provides tentative guidelines for expected balloon sizes and pressures for valve fracturing.

Check valve

Science.gov (United States)

Upton, H.A.; Garcia, P.

1999-08-24

A check valve for use in a GDCS of a nuclear reactor and having a motor driven disk including a rotatable armature for rotating the check valve disk over its entire range of motion is described. In one embodiment, the check valve includes a valve body having a coolant flow channel extending therethrough. The coolant flow channel includes an inlet end and an outlet end. A valve body seat is located on an inner surface of the valve body. The check valve further includes a disk assembly, sometimes referred to as the motor driven disc, having a counterweight and a disk shaped valve. The disk valve includes a disk base having a seat for seating with the valve body seat. The disk assembly further includes a first hinge pin member which extends at least partially through the disk assembly and is engaged to the disk. The disk valve is rotatable relative to the first hinge pin member. The check valve also includes a motor having a stator frame with a stator bore therein. An armature is rotatably positioned within the stator bore and the armature is coupled to the disk valve to cause the disk valve to rotate about its full range of motion. 5 figs.

Check valve

International Nuclear Information System (INIS)

Upton, H.A.; Garcia, P.

1999-01-01

A check valve for use in a GDCS of a nuclear reactor and having a motor driven disk including a rotatable armature for rotating the check valve disk over its entire range of motion is described. In one embodiment, the check valve includes a valve body having a coolant flow channel extending therethrough. The coolant flow channel includes an inlet end and an outlet end. A valve body seat is located on an inner surface of the valve body. The check valve further includes a disk assembly, sometimes referred to as the motor driven disc, having a counterweight and a disk shaped valve. The disk valve includes a disk base having a seat for seating with the valve body seat. The disk assembly further includes a first hinge pin member which extends at least partially through the disk assembly and is engaged to the disk. The disk valve is rotatable relative to the first hinge pin member. The check valve also includes a motor having a stator frame with a stator bore therein. An armature is rotatably positioned within the stator bore and the armature is coupled to the disk valve to cause the disk valve to rotate about its full range of motion. 5 figs

NRC valve performance test program - check valve testing

International Nuclear Information System (INIS)

Jeanmougin, N.M.

1987-01-01

The Valve Performance Test Program addresses the current requirements for testing of pressure isolation valves (PIVs) in light water reactors. Leak rate monitoring is the current method used by operating commercial power plants to survey the condition of their PIVs. ETEC testing of three check valves (4-inch, 6-inch, and 12-inch nominal diameters) indicates that leak rate testing is not a reliable method for detecting impending valve failure. Acoustic emission monitoring of check valves shows promise as a method of detecting loosened internals damage. Future efforts will focus on evaluation of acoustic emission monitoring as a technique for determining check valve condition. Three gate valves also will be tested to evaluate whether the check valve results are applicable to gate type PIVs

Transcatheter, valve-in-valve transapical aortic and mitral valve implantation, in a high risk patient with aortic and mitral prosthetic valve stenoses

Directory of Open Access Journals (Sweden)

Harish Ramakrishna

2015-01-01

Full Text Available Transcatheter valve implantation continues to grow worldwide and has been used principally for the nonsurgical management of native aortic valvular disease-as a potentially less invasive method of valve replacement in high-risk and inoperable patients with severe aortic valve stenosis. Given the burden of valvular heart disease in the general population and the increasing numbers of patients who have had previous valve operations, we are now seeing a growing number of high-risk patients presenting with prosthetic valve stenosis, who are not potential surgical candidates. For this high-risk subset transcatheter valve delivery may be the only option. Here, we present an inoperable patient with severe, prosthetic valve aortic and mitral stenosis who was successfully treated with a trans catheter based approach, with a valve-in-valve implantation procedure of both aortic and mitral valves.

Using Time-Driven Activity-Based Costing as a Key Component of the Value Platform: A Pilot Analysis of Colonoscopy, Aortic Valve Replacement and Carpal Tunnel Release Procedures

Science.gov (United States)

Martin, Jacob A.; Mayhew, Christopher R.; Morris, Amanda J.; Bader, Angela M.; Tsai, Mitchell H.; Urman, Richard D.

2018-01-01

Background Time-driven activity-based costing (TDABC) is a methodology that calculates the costs of healthcare resources consumed as a patient moves along a care process. Limited data exist on the application of TDABC from the perspective of an anesthesia provider. We describe the use of TDABC, a bottom-up costing strategy and financial outcomes for three different medical-surgical procedures. Methods In each case, a multi-disciplinary team created process maps describing the care delivery cycle for a patient encounter using the TDABC methodology. Each step in a process map delineated an activity required for delivery of patient care. The resources (personnel, equipment and supplies) associated with each step were identified. A per minute cost for each resource expended was generated, known as the capacity cost rate, and multiplied by its time requirement. The total cost for an episode of care was obtained by adding the cost of each individual resource consumed as the patient moved along a clinical pathway. Results We built process maps for colonoscopy in the gastroenterology suite, calculated costs of an aortic valve replacement by comparing surgical aortic valve replacement (SAVR) versus transcatheter aortic valve replacement (TAVR) techniques, and determined the cost of carpal tunnel release in an operating room versus an ambulatory procedure room. Conclusions TDABC is central to the value-based healthcare platform. Application of TDABC provides a framework to identify process improvements for health care delivery. The first case demonstrates cost-savings and improved wait times by shifting some of the colonoscopies scheduled with an anesthesiologist from the main hospital to the ambulatory facility. In the second case, we show that the deployment of an aortic valve via the transcatheter route front loads the costs compared to traditional, surgical replacement. The last case demonstrates significant cost savings to the healthcare system associated with re

Isolation valve control device for nuclear power plant

International Nuclear Information System (INIS)

Yukinori, Shigeru.

1990-01-01

The present invention provides an isolation valve control device for detecting pipeline rupture accidents in a BWR type nuclear power plant at an early stage to close an isolation valve thereby reducing the amout of radioactivity released to the circumstance. That is, isolation valves are disposed in the pipeline for each of the systems in the nuclear power plant and flow ratemeters are disposed to at least two positions in each of the pipelines. If a meaningful difference is shown for the measured values by these flow ratemeters, the isolation valve is closed. In this way, if pipeline rupture such as leak before break (LBB) is caused to a portion of a system pipelines, the measured value from the flow ratemeters at the downstream of the pipeline is lowered. Accordingly, when a meaningful difference is formed between the value of the flow ratematers at the upstream and the downstream, occurrence of pipe rutpture between both of the flow ratemeters can be detected. As a result, the isolation valves of the system can be closed. According to the present invention, it is possible to detect the pipeline rupture at an early stage irrespective of the kind of the systems, diameter of the pipelines and the magnitude of the ruptured area, and the isolation valve can be closed. (I.S.)

Development of magnetic drive packless valves for commercial purpose

International Nuclear Information System (INIS)

Hwang, Sung Tae; Park, Jin Ho; Choi, Yoon Dong; Choi, Jong Hyun; Cho, Byung Ryeol; Kim, Tae Jun; Moon, Byung Hwan; Hong, Soon Bok; Jeong, Ji Young

1995-09-01

A study on development of magnetic drive packless valves for commercial purpose showed the results as follows; 1. Study on the radial rays effecting to the permanent magnets -Measurement of the strength of Nd-magnets according to irradiation of radial rays. 2. Effects of temperature on the magnetic driving device -Temperature dependency of the Nd-casting magnets. -Effects of temperature on the heat releasing fins of high-temperature valve. 3. Optimization of torque -Arranging method of permanent magnets -Measuring method and results of torque. 4. Design, manufacture and test for the pressure-resisting structure of magnetic power transmitting device -Calculation and design for the flat circular plates under pressure of the magnetic power transmitting device -Design, manufacture and test for the pressure-resisting structure of magnetic power transmitting device -Comparison of the characteristics between magnetic drive valve and general/bellows-sealed valves. 5. Pressure test and strength analysis of flat circular plates under pressure. 6. Patent application. 12 tabs., 24 figs., 1 ref. (Author)

Heart valve surgery

Science.gov (United States)

... replacement; Valve repair; Heart valve prosthesis; Mechanical valves; Prosthetic valves ... surgery. Your heart valve has been damaged by infection ( endocarditis ). You have received a new heart valve ...

Voith Maxima: simulation-based throttle parameterisation; Voith Maxima: Simulationsbasierte Reglerparametrierung. Bei der Elektronik-Entwicklung der Lokomotive Voith Maxima wurden Methoden der Hardware-in-the-Loop-Simulation zur Reglerparametrierung eingesetzt

Energy Technology Data Exchange (ETDEWEB)

Schmidt, Thorsten; Hanke, Bjoern [IAV GmbH, Gifhorn (Germany). Powertrain Mechatronik; Jung, Eggert [Voith Turbo Lokomotiv Technik, Kiel (Germany)

2008-10-15

For fine-tuning of the diesel engine throttle control on the new Voith Maxima, IAV GmbH developed a physical Hardware-in-the-Loop simulation (HiL), whose parameterisation is based chiefly on easily obtainable construction design data. With the aid of the HiL simulation, the software functions of the of the engine's ECU could already be parameterised and verified in the lab, before a running prototype was available. As a result, a throttle application was available at an early stage, needing only to be further optimised during subsequent test runs. This enabled the number of driving trials, with the cost and effort involved, to be reduced. Looking to the future, an extended HiL simulation with an optimisation algorithm for automatic throttle parameterisation will allow for a further reduction in application development costs. (orig.)

Mathematical Modeling for Energy Dissipation Behavior of Velocity ...

African Journals Online (AJOL)

The developed oil-pressure damper is installed with an additional Relief Valve parallel to the Throttle Valve. This is intended to obtain an adaptive control by changing the damping coefficient of this damper using changeable orifice size. In order to simulate its actual energy-dissipating behavior, a serial friction model and a ...

Lipoprotein(a Induces Human Aortic Valve Interstitial Cell Calcification

Directory of Open Access Journals (Sweden)

Bin Yu, PhD

2017-08-01

Full Text Available Lipoprotein(a, or Lp(a, significantly increased alkaline phosphatase activity, release of phosphate, calcium deposition, hydroxyapatite, cell apoptosis, matrix vesicle formation, and phosphorylation of signal transduction proteins; increased expression of chondro-osteogenic mediators; and decreased SOX9 and matrix Gla protein (p < 0.001. Inhibition of MAPK38 and GSK3β significantly reduced Lp(a-induced calcification of human aortic valve interstitial cells (p < 0.001. There was abundant presence of Lp(a and E06 immunoreactivity in diseased human aortic valves. The present study demonstrates a causal effect for Lp(a in aortic valve calcification and suggests that interfering with the Lp(apathway could provide a novel therapeutic approach in the management of this debilitating disease.

A piezoelectric micro control valve with integrated capacitive sensing for ambulant blood pressure waveform monitoring

Science.gov (United States)

Groen, Maarten S.; Wu, Kai; Brookhuis, Robert A.; van Houwelingen, Marc J.; Brouwer, Dannis M.; Lötters, Joost C.; Wiegerink, Remco J.

2014-12-01

We have designed and characterized a MEMS microvalve with built-in capacitive displacement sensing and fitted it with a miniature piezoelectric actuator to achieve active valve control. The integrated displacement sensor enables high bandwidth proportional control of the gas flow through the valve. This is an essential requirement for non-invasive blood pressure waveform monitoring based on following the arterial pressure with a counter pressure. Using the capacitive sensor, we demonstrate negligible hysteresis in the valve control characteristics. Fabrication of the valve requires only two mask steps for deep reactive ion etching (DRIE) and one release etch.

A piezoelectric micro control valve with integrated capacitive sensing for ambulant blood pressure waveform monitoring

International Nuclear Information System (INIS)

Groen, Maarten S; Wu, Kai; Brookhuis, Robert A; Lötters, Joost C; Wiegerink, Remco J; Van Houwelingen, Marc J; Brouwer, Dannis M

2014-01-01

We have designed and characterized a MEMS microvalve with built-in capacitive displacement sensing and fitted it with a miniature piezoelectric actuator to achieve active valve control. The integrated displacement sensor enables high bandwidth proportional control of the gas flow through the valve. This is an essential requirement for non-invasive blood pressure waveform monitoring based on following the arterial pressure with a counter pressure. Using the capacitive sensor, we demonstrate negligible hysteresis in the valve control characteristics. Fabrication of the valve requires only two mask steps for deep reactive ion etching (DRIE) and one release etch. (paper)

Bioprosthetic Valve Fracture During Valve-in-valve TAVR: Bench to Bedside.

Science.gov (United States)

Saxon, John T; Allen, Keith B; Cohen, David J; Chhatriwalla, Adnan K

2018-01-01

Valve-in-valve (VIV) transcatheter aortic valve replacement (TAVR) has been established as a safe and effective means of treating failed surgical bioprosthetic valves (BPVs) in patients at high risk for complications related to reoperation. Patients who undergo VIV TAVR are at risk of patient-prosthesis mismatch, as the transcatheter heart valve (THV) is implanted within the ring of the existing BPV, limiting full expansion and reducing the maximum achievable effective orifice area of the THV. Importantly, patient-prosthesis mismatch and high residual transvalvular gradients are associated with reduced survival following VIV TAVR. Bioprosthetic valve fracture (BVF) is as a novel technique to address this problem. During BPV, a non-compliant valvuloplasty balloon is positioned within the BPV frame, and a highpressure balloon inflation is performed to fracture the surgical sewing ring of the BPV. This allows for further expansion of the BPV as well as the implanted THV, thus increasing the maximum effective orifice area that can be achieved after VIV TAVR. This review focuses on the current evidence base for BVF to facilitate VIV TAVR, including initial bench testing, procedural technique, clinical experience and future directions.

Performance and emission characteristics of a turbocharged spark-ignition hydrogen-enriched compressed natural gas engine under wide open throttle operating conditions

Energy Technology Data Exchange (ETDEWEB)

Ma, Fanhua; Wang, Mingyue; Jiang, Long; Deng, Jiao; Chen, Renzhe; Naeve, Nashay; Zhao, Shuli [State Key Laboratory of Automotive Safety and Energy, Tsinghua University, Beijing 100084 (China)

2010-11-15

This paper investigates the effect of various hydrogen ratios in HCNG (hydrogen-enriched compressed natural gas) fuels on performance and emission characteristics at wide open throttle operating conditions using a turbocharged spark-ignition natural gas engine. The experimental data was taken at hydrogen fractions of 0%, 30% and 55% by volume and was conducted under different excess air ratio ({lambda}) at MBT operating conditions. It is found that under various {lambda}, the addition of hydrogen can significantly reduce CO, CH{sub 4} emissions and the NO{sub x} emission remain at an acceptable level when ignition timing is optimized. Using the same excess air ratio, as more hydrogen is added the power, exhaust temperatures and max cylinder pressure decrease slowly until the mixture's lower heating value remains unchanged with the hydrogen enrichment, then they rise gradually. In addition, the early flame development period and the flame propagation duration are both shorter, and the indicated thermal efficiency and maximum heat release rate both increase with more hydrogen addition. (author)

Multifunctional four-port directional control valve constructed from logic valves

International Nuclear Information System (INIS)

Lisowski, E.; Czyżycki, W.; Rajda, J.

2014-01-01

Highlights: • Directional valve with standard ISO 440-08 has been constructed from logic valves. • Only one innovative valve may replace whole family of the standard valves. • CFD analysis and bench tests of the innovative valve has been carried. • Parameters of the innovative valve are equaling or surpassing the standard ones. • The innovative valve has additional possibilities of pressure and flow control. - Abstract: The paper refers to four-port solenoid pilot operated valves, which are subplate mounted in a hydraulic system in accordance with the ISO 4401 standard. Their widespread use in many machines and devices causes a continuing interest in the development of their design by both the scientific centers and the industry. This paper presents an innovative directional control valve based on the use of logic valves and a methodology followed for the design of it by using Solid Edge CAD and ANSYS/Fluent CFD software. The valve design methodology takes into account the need to seek solutions that minimize flow resistance through the valve. For this purpose, the flow paths are prepared by means of CAD software and pressure-flow curves are determined as a result of CFD analysis. The obtained curves are compared with the curves available in the catalogs of spool type directional control valves. The new solution allows to replace the whole family of spool type four-port directional control valves by one valve built of logic valves. In addition, the innovative directional control valve provides leak-proof shutting the flow paths off and also it can control flow rate and even pressure of working liquid. A prototype of the valve designed by the presented method has been made and tested on the test bench. The results quoted in the paper confirm that the developed logic type directional control valve is able to meet all designed connection configurations, and the obtained pressure-flow curves show very good conformity with the results of CFD analysis

Control Valve

Energy Technology Data Exchange (ETDEWEB)

Moore, Wayne R.

2018-03-20

A control valve includes a first conduit having a first inlet and a first outlet and defining a first passage; a second conduit having a second inlet and a second outlet and defining a second passage, the second conduit extending into the first passage such that the second inlet is located within the first passage; and a valve plate disposed pivotably within the first passage, the valve plate defining a valve plate surface. Pivoting of the valve plate within the first passage varies flow from the first inlet to the first outlet and the valve plate is pivotal between a first position and a second position such that in the first position the valve plate substantially prevents fluid communication between the first passage and the second passage and such that in the second position the valve plate permits fluid communication between the first passage and the second passage.

Mitral Valve Disease

Science.gov (United States)

... for mitral valve replacement—mechanical valves (metal) or biological valves (tissue). The principal advantage of mechanical valves ... small risk of stroke due to blood clotting. Biological valves usually are made from animal tissue. Biological ...

Sadhana | Indian Academy of Sciences

Indian Academy of Sciences (India)

A relief valve parallel to the throttle valve is added to a Velocity dependent hydraulic damper (VDHD) so that the orifice size that regulates the oil flow can be adjusted. This device adjustment will allow the damper to have an adaptive control of damping by changing its damping coefficient. A mathematical model including a ...

[Extracorporeal ventriculoatrial shunt with the use of one-way ball valve].

Science.gov (United States)

Kubo, Shigeki; Takimoto, Hiroshi; Hosoi, Kazuki; Toyota, Shingo; Takakura, Shuji; Hayashi, Yasuhiro; Ueno, Masato; Morisako, Toshitaka; Karasawa, Jun; Ninaga, Hideo; Yoshimine, Toshiki

2002-04-01

We developed a simple system of an "extracorporeal" ventriculoatrial (VA) shunt using a one-way ball valve (Acty valve II, Kaneka Medix) to release the patient from postoperative constraint during the ventricular drainage. The system is constructed in such a way that the ventricular drainage tube is connected to the central venous catheter via a one-way valve. The CSF is regulated by using the valve and is diverted into the systemic circulation as in the conventional ventriculoatrial shunt. After 2 or 3 weeks of CSF diversion through the extracorporeal VA shunt, a ventriculoperitoneal shunt is placed if hydrocephalus is apparent by temporary occlusion of the system. We applied this system to 4 patients with hydrocephalus, and we found it useful and free from adverse effects. The patient was freed from physical constraint involved in conventional ventricular drainage and an effective program of early rehabilitation was able to be started.

Skip cycle method with a valve-control mechanism for spark ignition engines

International Nuclear Information System (INIS)

Baykara, Cemal; Akin Kutlar, O.; Dogru, Baris; Arslan, Hikmet

2017-01-01

Highlights: • A normal four-stroke cycle followed by a skip cycle without gas exchange is tested. • The normal and skipped mode results are compared at equal power levels. • The throttle valve is opened wider, thereby resulting in a higher volumetric efficiency. • The pumping work during the gas exchange decreases significantly. • The fuel consumption (BSFC) is reduced by approximately 14–26% under part load conditions. - Abstract: The efficiency decrease of spark ignition (SI) engines under part-load conditions is a considerable issue. Changing the effective stroke volume based on the load level is one of the methods using to improve the part-load efficiency. In this study, a novel alternative engine valve control technique in order to perform a cycle without gas exchange (skip cycle), is examined. The goal of skip cycle strategy is to reduce the effective stroke volume of an engine under part load conditions by skipping several of the four stroke cycles by cutting off the fuel injection and simultaneously deactivating the inlet and exhaust valves. To achieve the same power level in the skip cycle, the cylinder pressure level reaches higher values compared to those in a normal four stroke cycle operation, but inherently not higher than the maximum one at full load of normal cycle. According to the experimental results, the break specific fuel consumption (BSFC) was reduced by 14–26% at a 1–3 bar break mean effective pressure (BMEP) and a 1200–1800 rpm engine speed of skip cycle operation, in comparison to normal engine operation. The significant decrease in the pumping work from the gas exchange is one of the primary factors for an increase in efficiency under part load conditions. As expected, the fuel consumption reduction rate at lower load conditions was higher. These experimental results indicate a promising potential of the skip cycle system for reducing the fuel consumption under part load conditions.

Valve thrombosis following transcatheter aortic valve implantation: a systematic review.

Science.gov (United States)

Córdoba-Soriano, Juan G; Puri, Rishi; Amat-Santos, Ignacio; Ribeiro, Henrique B; Abdul-Jawad Altisent, Omar; del Trigo, María; Paradis, Jean-Michel; Dumont, Eric; Urena, Marina; Rodés-Cabau, Josep

2015-03-01

Despite the rapid global uptake of transcatheter aortic valve implantation, valve trombosis has yet to be systematically evaluated in this field. The aim of this study was to determine the clinical characteristics, diagnostic criteria, and treatment outcomes of patients diagnosed with valve thrombosis following transcatheter aortic valve implantation through a systematic review of published data. Literature published between 2002 and 2012 on valve thrombosis as a complication of transcatheter aortic valve implantation was identified through a systematic electronic search. A total of 11 publications were identified, describing 16 patients (mean age, 80 [5] years, 65% men). All but 1 patient (94%) received a balloon-expandable valve. All patients received dual antiplatelet therapy immediately following the procedure and continued to take either mono- or dual antiplatelet therapy at the time of valve thrombosis diagnosis. Valve thrombosis was diagnosed at a median of 6 months post-procedure, with progressive dyspnea being the most common symptom. A significant increase in transvalvular gradient (from 10 [4] to 40 [12] mmHg) was the most common echocardiographic feature, in addition to leaflet thickening. Thrombus was not directly visualized with echocardiography. Three patients underwent valve explantation, and the remaining received warfarin, which effectively restored the mean transvalvular gradient to baseline within 2 months. Systemic embolism was not a feature of valve thrombosis post-transcatheter aortic valve implantation. Although a rare, yet likely under-reported complication of post-transcatheter aortic valve implantation, progressive dyspnea coupled with an increasing transvalvular gradient on echocardiography within the months following the intervention likely signifies valve thrombosis. While direct thrombus visualization appears difficult, prompt initiation of oral anticoagulation therapy effectively restores baseline valve function. Copyright © 2014

Tight valve

International Nuclear Information System (INIS)

Guedj, F.

1987-01-01

This sealed valve is made with a valve seat, an axial valve with a rod fixed to its upper end, a thick bell surrounding the rod and welded by a thin join on the valve casing, a threated ring screwed onto the upper end of the rod and a magnet or electromagnet rotating the ring outside the bell [fr

Aortic valve bypass

DEFF Research Database (Denmark)

Lund, Jens T; Jensen, Maiken Brit; Arendrup, Henrik

2013-01-01

In aortic valve bypass (AVB) a valve-containing conduit is connecting the apex of the left ventricle to the descending aorta. Candidates are patients with symptomatic aortic valve stenosis rejected for conventional aortic valve replacement (AVR) or transcatheter aortic valve implantation (TAVI). ...

An experimental investigation on reverse-cycle defrosting performance for an air source heat pump using an electronic expansion valve

International Nuclear Information System (INIS)

Qu, Minglu; Xia, Liang; Deng, Shiming; Jiang, Yiqiang

2012-01-01

Highlights: ► We experimentally studied the defrost performance under two EEV control strategies. ► The two EEV control strategies were fully open and controlled by a DS controller. ► When the EEV was under the DS controller, higher defrosting efficiency was obtained. -- Abstract: When an air source heat pump (ASHP) operates in heating mode, frost can be accumulated on the surface of its finned outdoor coil. Frosting deteriorates the operation and energy efficiency of the ASHP and periodic defrosting becomes necessary. Currently the most widely used standard defrosting method for ASHPs is reverse cycle defrost. On the other hand, electronic expansion valves (EEVs) are commonly used in heat pump/refrigeration systems, including ASHP units, as throttle regulators of refrigerant flow. This paper reports on an experimental investigation of the performance of a reverse cycle defrost operation for a 6.5 kW experimental heating capacity residential ASHP whose outdoor coil had four-parallel refrigerant circuits, and with an EEV as the refrigerant flow throttle regulator. The detailed descriptions of the experimental ASHP unit and the experimental procedures of ASHP are firstly presented. This is followed by reporting the comparative experiments of two control strategies for the EEV to investigate their effects on defrosting performance: the EEV being fully open and the EEV being regulated by a degree of refrigerant superheat (DS) controller. Experimental results revealed that when the EEV was regulated by the DS controller during defrosting, a higher defrosting efficiency and less heat wastage would be resulted in.

New safety valve addresses environmental concerns

International Nuclear Information System (INIS)

Taylor, J.; Austin, R.

1992-01-01

This paper reports that Conoco Pipeline is using a unique relief valve to reduce costs while improving environmental protection at its facilities. Conoco Pipeline Co. Inc. began testing new relief valves in 1987 to present over-pressuring its pipelines while enhancing the safety, environmental integrity and profitability of its pipelines. Conoco worked jointly with Rupture Pin Technology Inc., Oklahoma City, to seek a solution to a series of safety, environmental, and operational risks in the transportation of crude oil and refined products through pipelines. Several of the identified problems were traced to a single equipment source: the reliability of rupture discs used at pipeline stations to relieve pressure by diverting flow to tanks during over-pressure conditions. Conoco's corporate safety and environmental policies requires solving problems that deal with exposure to hydrocarbon vapors, chemical spills or the atmospheric release of fugitive emissions, such as during rupture disc maintenance. The company had used rupture pin valves as vent relief devices in conjunction with development by Rick Austin of inert gas methods to protect the inner casing wall and outer carrier pipeline wall in pipeline road crossings. The design relies on rupture pin valves set at 5 psi to isolate vent openings from the atmosphere prior to purging the annular space between the pipeline and casing with inert gas to prevent corrosion. Speciality Pipeline Inspection and Engineering Inc., Houston, is licensed to distribute the equipment for the new cased-crossing procedure

Transcatheter aortic valve implantation in failed bioprosthetic surgical valves

DEFF Research Database (Denmark)

Dvir, Danny; Webb, John G; Bleiziffer, Sabine

2014-01-01

for patients with structural valve deterioration; however, a comprehensive evaluation of survival after the procedure has not yet been performed. OBJECTIVE: To determine the survival of patients after transcatheter valve-in-valve implantation inside failed surgical bioprosthetic valves. DESIGN, SETTING......, stroke, and New York Heart Association functional class. RESULTS: Modes of bioprosthesis failure were stenosis (n = 181 [39.4%]), regurgitation (n = 139 [30.3%]), and combined (n = 139 [30.3%]). The stenosis group had a higher percentage of small valves (37% vs 20.9% and 26.6% in the regurgitation...... and combined groups, respectively; P = .005). Within 1 month following valve-in-valve implantation, 35 (7.6%) patients died, 8 (1.7%) had major stroke, and 313 (92.6%) of surviving patients had good functional status (New York Heart Association class I/II). The overall 1-year Kaplan-Meier survival rate was 83...

Dynamics of vibration isolation system with rubber-cord-pneumatic spring with damping throttle

Science.gov (United States)

Burian, Yu A.; Silkov, M. V.

2017-06-01

The study refers to the important area of applied mechanics; it is the theory of vibration isolation of vibroactive facilities. The design and the issues of mathematical modeling of pneumatic spring perspective design made on the basis of rubber-cord shell with additional volume connected with its primary volume by means of throttle passageway are considered in the text. Damping at the overflow of air through the hole limits the amplitude of oscillation at resonance. But in contrast to conventional systems with viscous damping it does not increase transmission ratio at high frequencies. The mathematical model of suspension allowing selecting options to reduce the power transmission ratio on the foundation, especially in the high frequency range is obtained

Multidetector computed tomography sizing of bioprosthetic valves: guidelines for measurement and implications for valve-in-valve therapies

International Nuclear Information System (INIS)

Rajani, R.; Attia, R.; Condemi, F.; Webb, J.; Woodburn, P.; Hodson, D.; Nair, A.; Preston, R.; Razavi, R.; Bapat, V.N.

2016-01-01

Aim: To describe a technique for bioprosthetic multidetector computed tomography (MDCT) sizing and to compare MDCT-derived values against manufacturer-provided sizing. Materials and methods: Fourteen bioprosthetic stented valves commonly used in the aortic valve position were evaluated using a Philips 256 MDCT system. All valves were scanned using a dedicated cardiac CT protocol with a four-channel electrocardiography (ECG) simulator. Measurements were made of major and minor axes and the area and perimeter of the internal stent using varying reconstruction kernels and window settings. Measurements derived from MDCT (MDCT ID) were compared against the stent internal diameter (Stent ID) as provided by the valve manufacturer and the True ID (Stent ID + insertion of leaflets). All data were collected and analysed using SPSS for Mac (version 21). Results: The mean difference between the MDCT ID and Stent ID was 0.6±1.9 mm (r=0.649, p=0.012) and between MDCT ID and True ID 2.1±2 mm (r=0.71, p=0.005). There was no difference in the major (p=0.90), minor (p=0.87), area (p=0.92), or perimeter (p=0.92) measurements when sharp, standard, and detailed stent kernels were used. Similarly, the measurements remained consistent across differing windowing levels. Conclusion: Bioprosthetic stented valves may be reliably sized using MDCT in patients requiring valve-in-valve (VIV) interventions where the valve type and size are unknown. In these cases, clinicians should be aware that MDCT has a tendency to overestimate the True ID size. - Highlights: • Cardiac CT is likely to be ideally suited for bioprosthetic aortic valve sizing for valve in valve procedures. • We compared MDCT sizing for 14 varying bioprosthetic aortic valves across varying window settings and reconstruction kernels. • We provide “normal” MDCT sizing for varying valves and show their relationship to surgical sizing. • Bioprosthetic valves may be reliably sized by MDCT but require adjustment owing to

Swing check valve

International Nuclear Information System (INIS)

Eminger, H.E.

1977-01-01

A swing check valve which includes a valve body having an inlet and outlet is described. A recess in the valve body designed to hold a seal ring and a check valve disc swingable between open and closed positions. The disc is supported by a high strength wire secured at one end in a support spacer pinned through bearing blocks fixed to the valve body and at its other end in a groove formed on the outer peripheral surface of the disc. The parts are designed and chosen such to provide a lightweight valve disc which is held open by minimum velocity of fluid flowing through the valve which thus reduces oscillations and accompanying wear of bearings supporting the valve operating parts. (Auth.)

Baking Powder Actuated Centrifugo-Pneumatic Valving for Automation of Multi-Step Bioassays

Directory of Open Access Journals (Sweden)

David J. Kinahan

2016-10-01

Full Text Available We report a new flow control method for centrifugal microfluidic systems; CO2 is released from on-board stored baking powder upon contact with an ancillary liquid. The elevated pressure generated drives the sample into a dead-end pneumatic chamber sealed by a dissolvable film (DF. This liquid incursion wets and dissolves the DF, thus opening the valve. The activation pressure of the DF valve can be tuned by the geometry of the channel upstream of the DF membrane. Through pneumatic coupling with properly dimensioned disc architecture, we established serial cascading of valves, even at a constant spin rate. Similarly, we demonstrate sequential actuation of valves by dividing the disc into a number of distinct pneumatic chambers (separated by DF membranes. Opening these DFs, typically through arrival of a liquid to that location on a disc, permits pressurization of these chambers. This barrier-based scheme provides robust and strictly ordered valve actuation, which is demonstrated by the automation of a multi-step/multi-reagent DNA-based hybridization assay.

Chemical Safety Alert: Shaft Blow-Out Hazard of Check and Butterfly Valves

Science.gov (United States)

Certain types of check and butterfly valves can undergo shaft-disk separation and fail catastrophically, even when operated within their design limits of pressure and temperature, causing toxic/flammable gas releases, fires, and vapor cloud explosions.

Valve Disease

Science.gov (United States)

... blood. There are 4 valves in the heart: tricuspid, pulmonary, mitral, and aortic. Two types of problems can disrupt blood flow through the valves: regurgitation or stenosis. Regurgitation is also called insufficiency or incompetence. Regurgitation happens when a valve doesn’ ...

241-AN-A valve pit manifold valves and position indication acceptance test procedure

Energy Technology Data Exchange (ETDEWEB)

VANDYKE, D.W.

1999-08-25

This document describes the method used to test design criteria for gear actuated ball valves installed in 241-AN-A Valve Pit located at 200E Tank Farms. The purpose of this procedure is to demonstrate the following: Equipment is properly installed, labeled, and documented on As-Built drawings; New Manifold Valves in the 241-AN-A Valve Pit are fully operable using the handwheel of the valve operators; New valve position indicators on the valve operators will show correct valve positions; New valve position switches will function properly; and New valve locking devices function properly.

Device for the catalytic after-burning of exhaust gases in the exhaust gas system of an internal-combustion engine

Energy Technology Data Exchange (ETDEWEB)

Lange, K

1975-06-19

The invention deals with a device which protects the catalyst for the after-burning of exhaust gases against damage by high temperatures. When the catalyst temperature reaches a certain limiting value, a throttle is activated by an electrical control device influenced by a temperature sensor via a servomotor. The throttle valve opens a by-pass for the exhaust gases which had previously flowed through the system for catalytic after-burning. In order to prevent the throttle from rusting due to its rare use, it is regularly put into use after switching off the ignition of the internal-combustion engine by the still briefly present oil pressure in the engine via an oil pressure switch and the mentioned control device.

Aortic Valve Stenosis

Science.gov (United States)

... most cases, doctors don't know why a heart valve fails to develop properly, so it isn't something you could have prevented. Calcium buildup on the valve. With age, heart valves may accumulate deposits of calcium (aortic valve ...

Valve assembly

International Nuclear Information System (INIS)

Sandling, M.

1981-01-01

An improved valve assembly, used for controlling the flow of radioactive slurry, is described. Radioactive contamination of the air during removal or replacement of the valve is prevented by sucking air from the atmosphere through a portion of the structure above the valve housing. (U.K.)

Effects of non-latching blast valves on the source term and consequences of the design-basis accidents in the Device Assembly Facility (DAF)

International Nuclear Information System (INIS)

Nguyen, D.H.

1993-08-01

The analysis of the Design-Basis Accidents (DBA) involving high explosives (HE) and Plutonium (Pu) in the assembly cell of the Device Assembly Facility (DAF), which was completed earlier, assumed latching blast valves in the ventilation system of the assembly cell. Latching valves effectively sealed a release path through the ventilation duct system. However, the blast valves in the assembly cell, as constructed are actually non-latching valves, and would reopen when the gas pressure drops to 0.5 psi above one atmosphere. Because the reopening of the blast valves provides an additional release path to the environment, and affects the material transport from the assembly cell to other DAF buildings, the DOE/NV DAF management has decided to support an additional analysis of the DAF's DBA to account for the effects of non-latching valves. Three cases were considered in the DAF's DBA, depending on the amount of HE and Pu involved, as follows: Case 1 -- 423 number-sign HE, 16 kg Pu; Case 2 -- 150 number-sign HE 10 kg Pu; Case 3 -- 55 number-sign HE 5 kg Pu. The results of the analysis with non-latching valves are summarized

Mitral Valve Stenosis

Science.gov (United States)

... the left ventricle from flowing backward. A defective heart valve fails to either open or close fully. Risk factors Mitral valve stenosis is less common today than it once was because the most common cause, ... other heart valve problems, mitral valve stenosis can strain your ...

Expression of uPA, tPA, and PAI-1 in Calcified Aortic Valves

Directory of Open Access Journals (Sweden)

Najlah Kochtebane

2014-01-01

Full Text Available Purpose. Our physiopathological assumption is that u-PA, t-PA, and PAI-1 are released by calcified aortic valves and play a role in the calcification of these valves. Methods. Sixty-five calcified aortic valves were collected from patients suffering from aortic stenosis. Each valve was incubated for 24 hours in culture medium. The supernatants were used to measure u-PA, t-PA, and PAI-1 concentrations; the valve calcification was evaluated using biphotonic absorptiometry. Results. Aortic stenosis valves expressed normal plasminogen activators concentrations and overexpressed PAI-1 (u-PA, t-PA, and PAI-1 mean concentrations were, resp., 1.69 ng/mL ± 0.80, 2.76 ng/mL ± 1.33, and 53.27 ng/mL ± 36.39. There was no correlation between u-PA and PAI-1 (r=0.3 but t-PA and PAI-1 were strongly correlated with each other (r=0.6. Overexpression of PAI-1 was proportional to the calcium content of the AS valves. Conclusions. Our results demonstrate a consistent increase of PAI-1 proportional to the calcification. The overexpression of PAI-1 may be useful as a predictive indicator in patients with aortic stenosis.

Structural valve deterioration in a starr-edwards mitral caged-disk valve prosthesis.

Science.gov (United States)

Aoyagi, Shigeaki; Tayama, Kei-Ichiro; Okazaki, Teiji; Shintani, Yusuke; Kono, Michitaka; Wada, Kumiko; Kosuga, Ken-Ichi; Mori, Ryusuke; Tanaka, Hiroyuki

2013-01-01

The durability of the Starr-Edwards (SE) mitral caged-disk valve, model 6520, is not clearly known, and structural valve deterioration in the SE disk valve is very rare. Replacement of the SE mitral disk valve was performed in 7 patients 23-40 years after implantation. Macroscopic examination of the removed disk valves showed no structural abnormalities in 3 patients, in whom the disk valves were removed at valves excised >36 years after implantation in 4 patients. Disk fracture, a longitudinal split in the disk along its circumference at the site of incorporation of the titanium ring, was detected in the valves removed 36 and 40 years after implantation, respectively, and many cracks were also observed on the outflow aspect of the disk removed 40 years after implantation. Disk fracture and localized disk wear were found in the SE mitral disk valves implanted >36 years previously. The present results suggest that SE mitral caged-disk valves implanted >20 years previously should be carefully followed up, and that those implanted >30 years previously should be electively replaced with modern prosthetic valves

Aortic valve replacement and the stentless Freedom SOLO valve

NARCIS (Netherlands)

Wollersheim, L.W.L.M.

2016-01-01

Aortic valve stenosis has become the most prevalent valvular heart disease in Europe and North America, and is generally caused by age-related calcification of the aortic valve. For most patients, severe symptomatic aortic stenosis needs effective mechanical relief in the form of valve replacement

Microfluidic sieve valves

Science.gov (United States)

Quake, Stephen R; Marcus, Joshua S; Hansen, Carl L

2015-01-13

Sieve valves for use in microfluidic device are provided. The valves are useful for impeding the flow of particles, such as chromatography beads or cells, in a microfluidic channel while allowing liquid solution to pass through the valve. The valves find particular use in making microfluidic chromatography modules.

Quantitative assessment of an aortic and pulmonary valve function according to valve fenestration

International Nuclear Information System (INIS)

Mirkhani, S.H.; Golestani, M.G.; Hosini, M.; Kazemian, A.

1999-01-01

There are some reasons for malfunction of aortic and pulmonary valve like fibrosis, calcification, and atheroma. Although, in some papers fenestration were known as a pathologic sign, but it is not generally accepted, while this matter is important in choosing suitable Homograft Heart Valve. In this paper fenestrations and its size, numbers and situation effect was studied. We collected 98 hearts, the donors died because of accident, we excluded valves with atheroma, calcification, fibrosis and unequal cusps, 91 aortic and 93 pulmonary valves were given further consideration. We classified valves according to situation, number and size of fenestration. Each valve was tested with 104 cm of non-nal saline column pressure which is equal to 76 mm Hg. Valve efficacy was detected by fluid flow assay. With study of 184 valves, 95 had no fenestration, 64 had less than 2 fenestration and 25 had more than 2 fenestration. Valve efficacy in condition of less than 2 fenestration was more than others (p <0.01). Malfunction effects of fenestration increased in larger valve and it will be decreased if their situation would be marginal (free margin of cusp). In the comparison of aortic and pulmonary valve we saw that malfunction effect of fenestration in pulmonary valve was more than aortic valve. Our experience in Immam Khomeini Homograft Valve Bank has shown that a great deal of valves is fenestrated. It seems that fenestration must be considered as a quality criterion in homograft valve preparation, especially in pulmonary and large aortic valves; but complementary studies is necessary

Sequential transcatheter aortic valve implantation due to valve dislodgement - a Portico valve implanted over a CoreValve bioprosthesis.

Science.gov (United States)

Campante Teles, Rui; Costa, Cátia; Almeida, Manuel; Brito, João; Sondergaard, Lars; Neves, José P; Abecasis, João; M Gabriel, Henrique

2017-03-01

Transcatheter aortic valve implantation (TAVI) has become an important treatment in high surgical risk patients with severe aortic stenosis (AS), whose complications need to be managed promptly. The authors report the case of an 86-year-old woman presenting with severe symptomatic AS, rejected for surgery due to advanced age and comorbidities. The patient underwent a first TAVI, with implantation of a Medtronic CoreValve ® , which became dislodged and migrated to the ascending aorta. Due to the previous balloon valvuloplasty, the patient's AS became moderate, and her symptoms improved. After several months, she required another intervention, performed with a St. Jude Portico ® repositionable self-expanding transcatheter aortic valve. There was a good clinical response that was maintained at one-year follow-up. The use of a self-expanding transcatheter bioprosthesis with repositioning features is a solution in cases of valve dislocation to avoid suboptimal positioning of a second implant, especially when the two valves have to be positioned overlapping or partially overlapping each other. Copyright © 2017 Sociedade Portuguesa de Cardiologia. Publicado por Elsevier España, S.L.U. All rights reserved.

Rotary pneumatic valve

Science.gov (United States)

Hardee, Harry C.

1991-01-01

A rotary pneumatic valve which is thrust balanced and the pneumatic pressure developed produces only radial loads on the valve cylinder producing negligible resistance and thus minimal torque on the bearings of the valve. The valve is multiplexed such that at least two complete switching cycles occur for each revolution of the cylinder spindle.

Scissor thrust valve actuator

Science.gov (United States)

DeWall, Kevin G.; Watkins, John C; Nitzel, Michael E.

2006-08-29

Apparatus for actuating a valve includes a support frame and at least one valve driving linkage arm, one end of which is rotatably connected to a valve stem of the valve and the other end of which is rotatably connected to a screw block. A motor connected to the frame is operatively connected to a motor driven shaft which is in threaded screw driving relationship with the screw block. The motor rotates the motor driven shaft which drives translational movement of the screw block which drives rotatable movement of the valve driving linkage arm which drives translational movement of the valve stem. The valve actuator may further include a sensory control element disposed in operative relationship with the valve stem, the sensory control element being adapted to provide control over the position of the valve stem by at least sensing the travel and/or position of the valve stem.

Heavy gas valves

Energy Technology Data Exchange (ETDEWEB)

Steier, L [Vereinigte Armaturen Gesellschaft m.b.H., Mannheim (Germany, F.R.)

1979-01-01

Heavy gas valves must comply with special requirements. Apart from absolute safety in operation there are stringent requirements for material, sealing and ease of operation even in the most difficult conditions. Ball valves and single plate pipe gate valves lateral sealing rings have a dual, double sided sealing effect according to the GROVE sealing system. Single plate gate valves with lateral protective plates are suitable preferably for highly contaminated media. Soft sealing gate valves made of cast iron are used for low pressure applications.

THE RESULTS OF SURGICAL TREATMENT OF TRICUSPID VALVE INFECTIVE ENDOCARDITIS USING VALVE REPAIR AND VALVE REPLACEMENT OPERATIONS

Directory of Open Access Journals (Sweden)

S. A. Kovalev

2015-01-01

Full Text Available Aim. To evaluate in-hospital and long-term results of surgical treatment of patients with infective endocarditis of the tricuspid valve, to compare the effectiveness of valve repair and valve replacement techniques, and to identify risk factors of mortality and reoperations. Materials and methods. 31 surgical patients with tricuspid valve infective endocarditis were evaluated. Patients were divided into 2 groups. In Group 1 (n = 14 repairs of the tricuspid valve were performed, in Group 2 (n = 17 patients had undergone tricuspid valve replacements. Epidemiological, clinical, microbiological and echocardiographic data were studied. Methods of comparative analysis, the Kaplan–Meier method, and Cox risk models were applied. Results. The most common complication of in-hospital stay was atrioventricular block (17.7% of cases in Group 2. In Group 1, this type of complication was not found. Hospital mortality was 7.14% in Group 1, and 0% in Group 2. Long-term results have shown the significant reduction of heart failure in general cohort and in both groups. In Group 1 the severity of heart failure in the long term was less than in Group 2. No significant differences in the severity of tricuspid regurgitation were found between the groups. In 7-year follow up no cases of death were registered in Group 1. Cumulative survival rate in Group 2 within 60 months was 67.3 ± 16.2%. No reoperations were performed in patients from Group 1. In Group 2, the freedom from reoperation within 60 months was 70.9 ± 15.3%. Combined intervention was found as predictor of postoperative mortality. Prosthetic valve endocarditis was identified as risk factor for reoperation. Conclusion. Valve repair and valve replacement techniques of surgical treatment of tricuspid valve endocarditis can provide satisfactory hospital and long-term results. Tricuspid valve repair techniques allowed reducing the incidence of postoperative atrioventricular block. In the long-term, patients

Prevention of crack initiation in valve bodies under thermal shock

Energy Technology Data Exchange (ETDEWEB)

Delmas, J.; Coppolani, P.

1996-12-01

On site and testing experience has shown that cracking in valves affects mainly the stellite hardfacing on seats and discs but may also be a concern for valve bodies. Metallurgical investigations conducted by EDF laboratories on many damaged valves have shown that most of the damage had either a chemical, manufacturing, or operating origin with a strong correlation between the origins and the type of damage. The chemical defects were either excess ferritic dilution of stellite or excess carburizing. Excess carburizing leads to a too brittle hardfacing which cracks under excessive stresses induced on the seating surfaces, via the stem, by too high operating thrusts. The same conditions can also induce cracks of the seats in the presence, in the hardfacing, of hidden defects generated during the welding process. Reduction of the number of defects results first from controls during manufacturing, mainly in the thickness of stellite. On the other hand, maintenance must be fitted to the type of defect. In-situ lapping may lead to release of cobalt, resulting in contamination of the circuit. Furthermore, it is ineffectual in the case of a crack through the seating surface, as is often found on globe valves. The use of new technologies of valves with removable seats and cobalt-free alloys solves permanently this kind of problem.

Numerical study of saturation steam/water mixture flow and flashing initial sub-cooled water flow inside throttling devices

CERN Multimedia

CERN. Geneva

2016-01-01

In this work, a Computational Fluid-Dynamics (CFD) approach to model this phenomenon inside throttling devices is proposed. To validate CFD results, different nozzle geometries are analyzed, comparing numerical results with experimental data. Two cases are studied: Case 1: saturation steam/water mixture flow inside 2D convergent-divergent nozzle (inlet, outlet and throat diameter of nozzle are 0.1213m, 0.0452m and 0.0191m respectively). In this benchmark, a range of total inle...

Numerical simulation and analysis of ball valve three-dimensional flow based on CFD

International Nuclear Information System (INIS)

Zhang, S C; Zhang, Y L; Fang, Z M

2012-01-01

The new rotor oil-gas mixture pump that added ball valves in its export is a kind of innovative products, which can better adapt to the oil and gas mixed condition. In order to explore the rule of flow field in the export ball valve of new rotor oil-gas mixture pump, established the 3 d model of ball valve flow field was established. Using the FLUENT software, combining the standard k-ε turbulent model with multiphase flow technology and adopting the SIMPLE algorithm to simulate the 3 d gas-liquid two phase flow field in export ball valve of new rotor oil-gas mixture pump. In the different conditions that the volume of gas rate was 25%, 50%, 75%, through analyzing the velocity field, stress field and the distribution of the liquid and gas with the ball valve open height respectively at 3mm, 5mm, 7mm. Discussed how open height and different volume of gas rate to influence the field in export ball valve in the process of gas-liquid mixing was discussed. The simulation results showed that the greater the open height, the smaller the difference pressure of ball valve; the gap velocity decreasing with the open height increasing. The gas is mainly distributed in the vicinity of the valve ball in the process of gas-liquid mixing. The gas liquid ratio has a little effect on the gap velocity in the same open height. The results showed the flow field forms in the ball valve directly, to a certain degree, it had released the rules of gas-liquid flow in the valve and provided the theoretical guidance for design and optimization of the new rotor oil-gas mixture pump export ball valve.

Force measuring valve assemblies, systems including such valve assemblies and related methods

Science.gov (United States)

DeWall, Kevin George [Pocatello, ID; Garcia, Humberto Enrique [Idaho Falls, ID; McKellar, Michael George [Idaho Falls, ID

2012-04-17

Methods of evaluating a fluid condition may include stroking a valve member and measuring a force acting on the valve member during the stroke. Methods of evaluating a fluid condition may include measuring a force acting on a valve member in the presence of fluid flow over a period of time and evaluating at least one of the frequency of changes in the measured force over the period of time and the magnitude of the changes in the measured force over the period of time to identify the presence of an anomaly in a fluid flow and, optionally, its estimated location. Methods of evaluating a valve condition may include directing a fluid flow through a valve while stroking a valve member, measuring a force acting on the valve member during the stroke, and comparing the measured force to a reference force. Valve assemblies and related systems are also disclosed.

Magnetically operated check valve

Science.gov (United States)

Morris, Brian G.; Bozeman, Richard J., Jr.

1994-06-01

A magnetically operated check valve is disclosed. The valve is comprised of a valve body and a movable poppet disposed therein. A magnet attracts the poppet to hold the valve shut until the force of fluid flow through the valve overcomes the magnetic attraction and moves the poppet to an unseated, open position. The poppet and magnet are configured and disposed to trap a magnetically attracted particulate and prevent it from flowing to a valve seating region.

A remote control valve

International Nuclear Information System (INIS)

Cachard, Maurice de; Dumont, Maurice.

1976-01-01

This invention concerns a remote control valve for shutting off or distributing a fluid flowing at a high rate and low pressure. Among the different valves at present in use, electric valves are the most recommended for remote control but their reliability is uncertain and they soon become costly when large diameter valves are used. The valve described in this invention does away with this drawback owing to its simplicity and the small number of moving parts, this makes it particularly reliable. It mainly includes: a tubular body fitted with at least one side opening; at least one valve wedge for this opening, coaxial with the body, and mobile; a mobile piston integral with this wedge. Several valves to the specifications of this invention can be fitted in series (a shut-off valve can be used in conjunction with one or more distribution valves). The fitting and maintenance of the valve is very simple owing to its design. It can be fabricated in any material such as metals, alloys, plastics and concrete. The structure of the valve prevents the flowing fluid from coming into contact with the outside environment, thereby making it particularly suitable in the handling of dangerous or corrosive fluids. Finally, the opening and shutting of the valve occurs slowly, thereby doing away with the water hammer effect so frequent in large bore pipes [fr

Infective Endocarditis of the Aortic Valve with Anterior Mitral Valve Leaflet Aneurysm

NARCIS (Netherlands)

Tomsic, Anton; Li, Wilson W. L.; van Paridon, Marieke; Bindraban, Navin R.; de Mol, Bas A. J. M.

2016-01-01

Mitral valve leaflet aneurysm is a rare and potentially devastating complication of aortic valve endocarditis. We report the case of a 48-year-old man who had endocarditis of the native aortic valve and a concomitant aneurysm of the anterior mitral valve leaflet. Severe mitral regurgitation occurred

Aortic valve insufficiency in the teenager and young adult: the role of prosthetic valve replacement.

Science.gov (United States)

Bradley, Scott M

2013-10-01

The contents of this article were presented in the session "Aortic insufficiency in the teenager" at the congenital parallel symposium of the 2013 Society of Thoracic Surgeons (STS) annual meeting. The accompanying articles detail the approaches of aortic valve repair and the Ross procedure.(1,2) The current article focuses on prosthetic valve replacement. For many young patients requiring aortic valve surgery, either aortic valve repair or a Ross procedure provides a good option. The advantages include avoidance of anticoagulation and potential for growth. In other patients, a prosthetic valve is an appropriate alternative. This article discusses the current state of knowledge regarding mechanical and bioprosthetic valve prostheses and their specific advantages relative to valve repair or a Ross procedure. In current practice, young patients requiring aortic valve surgery frequently undergo valve replacement with a prosthetic valve. In STS adult cardiac database, among patients ≤30 years of age undergoing aortic valve surgery, 34% had placement of a mechanical valve, 51% had placement of a bioprosthetic valve, 9% had aortic valve repair, and 2% had a Ross procedure. In the STS congenital database, among patients 12 to 30 years of age undergoing aortic valve surgery, 21% had placement of a mechanical valve, 18% had placement of a bioprosthetic valve, 30% had aortic valve repair, and 24% had a Ross procedure. In the future, the balance among these options may be altered by design improvements in prosthetic valves, alternatives to warfarin, the development of new patch materials for valve repair, and techniques to avoid Ross autograft failure.

75 FR 29723 - Foreign-Trade Zone 29-Louisville, KY; Application for Expansion and Expansion of Manufacturing...

Science.gov (United States)

2010-05-27

... distribution of various automotive components, including mass air sensors, throttle bodies and chambers..., plates, filters, bearings, air pumps/compressors, valves, switches, electric motors, tubes/pipes/profiles... modules, rotors/stators, ignition coils, electronic sensors and modules, fuel injectors, emissions control...

Transcatheter aortic valve-in-valve treatment of degenerative stentless supra-annular Freedom Solo valves: A single centre experience.

Science.gov (United States)

Cockburn, James; Dooley, Maureen; Parker, Jessica; Hill, Andrew; Hutchinson, Nevil; de Belder, Adam; Trivedi, Uday; Hildick-Smith, David

2017-02-15

Redo surgery for degenerative bioprosthetic aortic valves is associated with significant morbidity and mortality. Report results of valve-in-valve therapy (ViV-TAVI) in failed supra-annular stentless Freedom Solo (FS) bioprostheses, which are the highest risk for coronary occlusion. Six patients with FS valves (mean age 78.5 years, 50% males). Five had valvular restenosis (peak gradient 87.2 mm Hg, valve area 0.63 cm 2 ), one had severe regurgitation (AR). Median time to failure was 7 years. Patients were high risk (mean STS/Logistic EuroScore 10.6 15.8, respectively). FS valves ranged from 21 to 25 mm. Successful ViV-TAVI was achieved in 4/6 patients (67%). Of the unsuccessful cases, (patient 1 and 2 of series) patient 1 underwent BAV with simultaneous aortography which revealed left main stem occlusion. The procedure was stopped and the patient went forward for repeat surgery. Patient 2 underwent successful ViV-TAVI with a 26-mm CoreValve with a guide catheter in the left main, but on removal coronary obstruction occurred, necessitating valve snaring into the aorta. Among the successful cases, (patients 3, 4, 5, 6) the TAVIs used were CoreValve Evolut R 23 mm (n = 3), and Lotus 23 mm (n = 1). In the successful cases the peak gradient fell from 83.0 to 38.3 mm Hg. No patient was left with >1+ AR. One patient had a stroke on Day 2, with full neurological recovery. Two patients underwent semi-elective pacing for LBBB and PR >280 ms. ViV-TAVI in stentless Freedom Solo valves is high risk. The risk of coronary occlusion is high. The smallest possible prosthesis (1:1 sizing) should be used, and strategies to protect the coronary vessels must be considered. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

A remotely operated drug delivery system with an electrolytic pump and a thermo-responsive valve

KAUST Repository

Yi, Ying

2015-07-22

Implantable drug delivery devices are becoming attractive due to their abilities of targeted and controlled dose release. Currently, two important issues are functional lifetime and non-controlled drug diffusion. In this work, we present a drug delivery device combining an electrolytic pump and a thermo-responsive valve, which are both remotely controlled by an electromagnetic field (40.5 mT and 450 kHz). Our proposed device exhibits a novel operation mechanism for long-term therapeutic treatments using a solid drug in reservoir approach. Our device also prevents undesired drug liquid diffusions. When the electromagnetic field is on, the electrolysis-induced bubble drives the drug liquid towards the Poly (N-Isopropylacrylamide) (PNIPAM) valve that consists of PNIPAM and iron micro-particles. The heat generated by the iron micro-particles causes the PNIPAM to shrink, resulting in an open valve. When the electromagnetic field is turned off, the PNIPAM starts to swell. In the meantime, the bubbles are catalytically recombined into water, reducing the pressure inside the pumping chamber, which leads to the refilling of the fresh liquid from outside the device. A catalytic reformer is included, allowing more liquid refilling during the limited valve\\'s closing time. The amount of body liquid that refills the drug reservoir can further dissolve the solid drug, forming a reproducible drug solution for the next dose. By repeatedly turning on and off the electromagnetic field, the drug dose can be cyclically released, and the exit port of the device is effectively controlled.

Design and performance characteristic analysis of servo valve-type water hydraulic poppet valve

International Nuclear Information System (INIS)

Park, Sung Hwan

2009-01-01

For water hydraulic system control, the flow or pressure control using high-speed solenoid valve controlled by PWM control method could be a good solution for prevention of internal leakage. However, since the PWM control of on-off valves cause extensive flow and pressure fluctuation, it is difficult to control the water hydraulic actuators precisely. In this study, the servo valve-type water hydraulic valve using proportional poppet as the main valve is designed and the performance characteristics of the servo valve-type water hydraulic valve are analyzed. Furthermore, it is demonstrated through experiments that a decline in control chamber pressure that follows the change of pilot flow is caused by the occurrence of cavitation around the proportional poppet, and that fundamental characteristics of the developed valve remain unaffected by the occurrence of cavitation

Which valve is which?

Directory of Open Access Journals (Sweden)

Pravin Saxena

2015-01-01

Full Text Available A 25-year-old man presented with a history of breathlessness for the past 2 years. He had a history of operation for Tetralogy of Fallot at the age of 5 years and history suggestive of Rheumatic fever at the age of 7 years. On echocardiographic examination, all his heart valves were severely regurgitating. Morphologically, all the valves were irreparable. The ejection fraction was 35%. He underwent quadruple valve replacement. The aortic and mitral valves were replaced by metallic valve and the tricuspid and pulmonary by tissue valve.

Mitral Valve Prolapse

Science.gov (United States)

Mitral valve prolapse (MVP) occurs when one of your heart's valves doesn't work properly. The flaps of the valve are "floppy" and ... to run in families. Most of the time, MVP doesn't cause any problems. Rarely, blood can ...

Maximizing prosthetic valve size with the Top Hat supra-annular aortic valve

DEFF Research Database (Denmark)

Aagaard, Jan; Geha, Alexander S.

2007-01-01

BACKGROUND AND AIM OF THE STUDY: The CarboMedics Top Hat supra-annular aortic valve allows a one-size (and often two-size) increase over the standard intra-annular valve. This advantage should minimize the risk of patient-prosthesis mismatch, where the effective prosthetic valve orifice area....... This study evaluates the authors' clinical experience with Top Hat supra-annular aortic valve size selection, and the technical aspects of implantation. METHODS: Between January 1999 and October 2005, a total of 251 consecutive patients underwent 252 aortic valve replacements with Top Hat supra...... required unplanned coronary bypass, and 30-day mortality was 2.0% (5/251), indicating a good safety profile for the valves implanted in this series. CONCLUSION: The general distribution of implant sizes in the US indicates that cardiac surgeons may be under-sizing the Top Hat supra-annular aortic valve...

AREVA's innovative solutions for valve diagnostics and in-situ valve repair

International Nuclear Information System (INIS)

Damies, H.; Breitenberger, U.; Munoz, L.; Kostroun, F.

2012-01-01

Optimized maintenance strategies are a key aspect for safe and undisturbed plant operation. Innovative valve service solutions can support that in an efficient way. The ADAM®/SIPLUG® valve monitoring system allows full online monitoring of valves and actuators with automatic evaluation and assessment. Especially for safety-related and operation-related valves this provides valuable information on components condition to ensure proper function and contribute to optimization of maintenance strategies as well as effective maintenance performance. More than 25 years of experience in various plants worldwide show that application of ADAM®/SIPLUG® valve diagnostics solution leads to increased plant safety and availability. With the innovative AVARIS technology an in-situ valve repair is possible. It has the unique ability to conduct several steps in-situ, to maintain the sealing seat of gate or check valves. By applying AVARIS, the valve is restored in its original state, the system remains unchanged. Thus, all original documents remain valid and applicable. In comparison to previous procedures like cutting valves out of the pipeline and repairing hard facings or damaged seal seats in a separate workshop or alternatively replacement by a new valve body the new AVARIS technology avoids costs, risk and effort. (author)

Heart Valve Diseases

Science.gov (United States)

Your heart has four valves. Normally, these valves open to let blood flow through or out of your heart, and then shut to keep it from flowing ... close tightly. It's one of the most common heart valve conditions. Sometimes it causes regurgitation. Stenosis - when ...

Prosthetic valve endocarditis after transcatheter aortic valve implantation

DEFF Research Database (Denmark)

Olsen, Niels Thue; De Backer, Ole; Thyregod, Hans G H

2015-01-01

BACKGROUND: Transcatheter aortic valve implantation (TAVI) is an advancing mode of treatment for inoperable or high-risk patients with aortic stenosis. Prosthetic valve endocarditis (PVE) after TAVI is a serious complication, but only limited data exist on its incidence, outcome, and procedural......%) were treated conservatively and 1 with surgery. Four patients (22%) died from endocarditis or complications to treatment, 2 of those (11%) during initial hospitalization for PVE. An increased risk of TAVI-PVE was seen in patients with low implanted valve position (hazard ratio, 2.8 [1.1-7.2]), moderate...

Valve monitoring ITI-MOVATS

International Nuclear Information System (INIS)

Moureau, S.

1993-01-01

ITI-MOVATS provides a wide range of test devices to monitor the performance of valves: motor operated gate or globe valve, butterfly valve, air operated valve, and check valve. The ITI-MOVATS testing equipment is used in the following three areas: actuator setup/baseline testing, periodic/post-maintenance testing, and differential pressure testing. The parameters typically measured with the MOVATS diagnostic system as well as the devices used to measure them are described. (Z.S.)

The nordic aortic valve intervention (NOTION) trial comparing transcatheter versus surgical valve implantation

DEFF Research Database (Denmark)

Thyregod, Hans Gustav; Søndergaard, Lars; Ihlemann, Nikolaj

2013-01-01

Degenerative aortic valve (AV) stenosis is the most prevalent heart valve disease in the western world. Surgical aortic valve replacement (SAVR) has until recently been the standard of treatment for patients with severe AV stenosis. Whether transcatheter aortic valve implantation (TAVI) can...

Gasoline New Timing and Flux Adjustable Rotary Valve Design (Hereinafter: Rotary Valve

Directory of Open Access Journals (Sweden)

Du huiqi

2016-01-01

Full Text Available Conventional gasoline engine with an umbrella valve control cylinder intake and exhaust, in order to achieve sealing effect, the valve is driven by the spring force; at the same time, when the cam opens the valve to overcome the spring force acting. Sealing the better, the more power consumed in the engine mechanical losses, the valve mechanism consumes about 30%, which is not a small loss! This article describes a new type of rotary valve is to significantly reduce mechanical losses, so as to achieve energy saving purposes.

Fluid control valves

International Nuclear Information System (INIS)

Rankin, J.

1980-01-01

A fluid control valve is described in which it is not necessary to insert a hand or a tool into the housing to remove the valve seat. Such a valve is particularly suitable for the control of radioactive fluids since maintenance by remote control is possible. (UK)

What Is Heart Valve Surgery?

Science.gov (United States)

... working correctly. Most valve replacements involve the aortic Tricuspid valve and mitral valves. The aortic valve separates ... where it shouldn’t. This is called incompetence, insufficiency or regurgitation. • Prolapse — mitral valve flaps don’t ...

What Is Heart Valve Disease?

Science.gov (United States)

... and replacing it with a man-made or biological valve. Biological valves are made from pig, cow, or human ... the valve. Man-made valves last longer than biological valves and usually don’t have to be ...

Relief valve testing study

International Nuclear Information System (INIS)

BROMM, R.D.

2001-01-01

Reclosing pressure-actuated valves, commonly called relief valves, are designed to relieve system pressure once it reaches the set point of the valve. They generally operate either proportional to the differential between their set pressure and the system pressure (gradual lift) or by rapidly opening fully when the set pressure is reached (pop action). A pop action valve allows the maximum fluid flow through the valve when the set pressure is reached. A gradual lift valve allows fluid flow in proportion to how much the system pressure has exceeded the set pressure of the valve (in the case of pressure relief) or has decreased below the set pressure (vacuum relief). These valves are used to protect systems from over and under pressurization. They are used on boilers, pressure vessels, piping systems and vacuum systems to prevent catastrophic failures of these systems, which can happen if they are under or over pressurized beyond the material tolerances. The construction of these valves ranges from extreme precision of less than a psi tolerance and a very short lifetime to extremely robust construction such as those used on historic railroad steam engines that are designed operate many times a day without changing their set pressure when the engines are operating. Relief valves can be designed to be immune to the effects of back pressure or to be vulnerable to it. Which type of valve to use depends upon the design requirements of the system

Demonstration of containment purge and vent valve operability for the Hope Creek Generating Station, Unit 1 (Docket No. 50-354)

International Nuclear Information System (INIS)

Kido, C.

1985-05-01

The containment purge and vent valve qualification program for the Hope Creek Generating Station has been reviewed by the NRC Licensing Support Section. The review indicates that the licensee has demonstrated the dependability of containment isolation against the buildup of containment pressure due to a LOCA/DBA with the restrictions that during operating conditions 1, 2, and 3 all purge and vent valves will be sealed closed and under administrative control, and during power ascension and descension conditions the 26 in. inboard valve (1-GS-HV-4952) will be used in series with the 2 in. bypass valve (1-GS-HV-4951) to control the release of containment pressure

Comparative study between CardiaMed valves (freely floating valve leaflets versus St. Jude Medical (fixed valve leaflets in mitral valve replacement surgery

Directory of Open Access Journals (Sweden)

Mostafa Ahmed

2017-09-01

Conclusions: CardiaMed freely floating leaflet prostheses showed good hemodynamic characteristics. The prosthesis adequately corrects hemodynamics and is safe and no worse than the St. Jude Medical valve in the mitral valve position.

Face-Sealing Butterfly Valve

Science.gov (United States)

Tervo, John N.

1992-01-01

Valve plate made to translate as well as rotate. Valve opened and closed by turning shaft and lever. Interactions among lever, spring, valve plate, and face seal cause plate to undergo combination of translation and rotation so valve plate clears seal during parts of opening and closing motions.

Transapical JenaValve in a patient with mechanical mitral valve prosthesis.

LENUS (Irish Health Repository)

O' Sullivan, Katie E

2014-01-29

We report the first case of transcatheter aortic valve replacement implantation using JenaValve™ in a patient with mechanical mitral valve prosthesis. We believe that the design features of this valve may be particularly suited for use in this setting. © 2014 Wiley Periodicals, Inc.

Butterfly valves for seawater

International Nuclear Information System (INIS)

Yamanaka, Katsuto

1991-01-01

Recently in thermal and nuclear power stations and chemical plants which have become large capacity, large quantity of cooling water is required, and mostly seawater is utilized. In these cooling water systems, considering thermal efficiency and economy, the pipings become complex, and various control functions are demanded. For the purpose, the installation of shut-off valves and control valves for pipings is necessary. The various types of valves have been employed, and in particular, butterfly valves have many merits in their function, size, structure, operation, maintenance, usable period, price and so on. The corrosion behavior of seawater is complicated due to the pollution of seawater, therefore, the environment of the valves used for seawater became severe. The structure and the features of the butterfly valves for seawater, the change of the structure of the butterfly valves for seawater and the checkup of the butterfly valves for seawater are reported. The corrosion of metallic materials is complicatedly different due to the locating condition of plants, the state of pipings and the condition of use. The corrosion countermeasures for butterfly valves must be examined from the synthetic viewpoints. (K.I.)

Supra-annular valve strategy for an early degenerated transcatheter balloon-expandable heart valve.

Science.gov (United States)

Kamioka, Norihiko; Caughron, Hope; Corrigan, Frank; Block, Peter; Babaliaros, Vasilis

2018-01-23

Currently, there are no recommendations regarding the selection of valve type for a transcatheter heart valve (THV)-in-THV procedure. A supra-annular valve design may be superior in that it results in a larger effective orifice area and may have a lower chance of valve thrombosis after THV-in-THV. In this report, we describe the use of a supra-annular valve strategy for an early degenerated THV. © 2018 Wiley Periodicals, Inc.

Shuttle Gaseous Hydrogen Venting Risk from Flow Control Valve Failure

Science.gov (United States)

Drummond, J. Philip; Baurle, Robert A.; Gafney, Richard L.; Norris, Andrew T.; Pellett, Gerald L.; Rock, Kenneth E.

2009-01-01

This paper describes a series of studies to assess the potential risk associated with the failure of one of three gaseous hydrogen flow control valves in the orbiter's main propulsion system during the launch of Shuttle Endeavour (STS-126) in November 2008. The studies focused on critical issues associated with the possibility of combustion resulting from release of gaseous hydrogen from the external tank into the atmosphere during assent. The Shuttle Program currently assumes hydrogen venting from the external tank will result in a critical failure. The current effort was conducted to increase understanding of the risk associated with venting hydrogen given the flow control valve failure scenarios being considered in the Integrated In-Flight Anomaly Investigation being conducted by NASA.

Remote actuated valve implant

Science.gov (United States)

McKnight, Timothy E; Johnson, Anthony; Moise, Jr., Kenneth J; Ericson, Milton Nance; Baba, Justin S; Wilgen, John B; Evans, III, Boyd McCutchen

2014-02-25

Valve implant systems positionable within a flow passage, the systems having an inlet, an outlet, and a remotely activatable valve between the inlet and outlet, with the valves being operable to provide intermittent occlusion of the flow path. A remote field is applied to provide thermal or magnetic activation of the valves.

Fuel control apparatus of carburetor in deceleration

Energy Technology Data Exchange (ETDEWEB)

Ishii, N

1974-11-20

A fuel control valve for carburetors during deceleration operation is described for fuel conservation. The device cuts off the fuel supply to the cylinder during deceleration. The control valve is regulated by a magnetic switch, and the electrical current to the switch is controlled through a device sensible to the pressure difference to both sides of the throttle valve in the carburetor. When the cylinder becomes lower in pressure than the atmospheric pressure, the pressure activates the electrical current switch, thus activating the magnetic switch to close the fuel control valve. The device also prevents the engine from running after the ignition key is disconnected.

Modeling valve leakage

International Nuclear Information System (INIS)

Bell, S.R.; Rohrscheib, R.

1994-01-01

The American Society of Mechanical Engineers (ASME) Code requires individual valve leakage testing for Category A valves. Although the U.S. Nuclear Regulatory Commission (USNRC) has recognized that it is more appropriate to test containment isolation valves in groups, as allowed by 10 CFR 50, Appendix J, a utility seeking relief from these Code requirements must provide technical justification for the relief and establish a conservative alternate acceptance criteria. In order to provide technical justification for group testing of containment isolation valves, Illinois Power developed a calculation (model) for determining the size of a leakage pathway in a valve disc or seat for a given leakage rate. The model was verified experimentally by machining leakage pathways of known size and then measuring the leakage and comparing this value to the calculated value. For the range of values typical of leakage rate testing, the correlation between the experimental values and calculated values was quote good. Based upon these results, Illinois Power established a conservative acceptance criteria for all valves in the inservice testing (IST) program and was granted relief by the USNRC from the individual leakage testing requirements of the ASME Code. This paper presents the results of Illinois Power's work in the area of valve leakage rate testing

Use of a valve operation test and evaluation system to enhance valve reliability

International Nuclear Information System (INIS)

Lowry, D.A.

1990-01-01

Power plant owners have emphasized the need for assuring safe, reliable operation of valves. While most valves must simply open or close, the mechanisms involved can be quite complex. Motor operated valves (MOVs) must be properly adjusted to assure operability. Individual operator components determine the performance of the entire MOV. Failure in MOVs could cripple or shut down a unit. Thus, a complete valve program consisting of design reviews, operational testing, and preventive and predictive maintenance activities will enhance an owner's confidence level that his valves win operate as expected. Liberty's Valve Operation Test and Evaluation System (VOTES) accurately measures stein thrust without intruding on valve operation. Since mounting a strain gage to a valve stem is a desirable but impractical way of obtaining precise stem thrust, Liberty developed a method to obtain identical data by placing a strain gage sensor on the valve yoke. VOTES provides information which effectively eliminates costly, unscheduled downtime. This paper presents the results of infield VOTES testing. The system's proven ability to identify and characterize actuator and valve performance is demonstrated. Specific topics of discussion include the ability of VOTES to ease a utility's IE Bulletin 8543 concerns and conclusively diagnose MOV components. Data from static and differential pressure testing are presented. Technical, operational, and financial advantages resulting from VOTES technology are explored in detail

Multiple-port valve

International Nuclear Information System (INIS)

Doody, T.J.

1978-01-01

A multiple-port valve assembly is designed to direct flow from a primary conduit into any one of a plurality of secondary conduits as well as to direct a reverse flow. The valve includes two mating hemispherical sockets that rotatably receive a spherical valve plug. The valve plug is attached to the primary conduit and includes diverging passageways from that conduit to a plurality of ports. Each of the ports is alignable with one or more of a plurality of secondary conduits fitting into one of the hemispherical sockets. The other hemispherical socket includes a slot for the primary conduit such that the conduit's motion along that slot with rotation of the spherical plug about various axes will position the valve-plug ports in respect to the secondary conduits

Pilot-in-the-Loop Evaluation of a Yaw Rate to Throttle Feedback Control with Enhanced Engine Response

Science.gov (United States)

Litt, Jonathan S.; Guo, Ten-Huei; Sowers, T. Shane; Chicatelli, Amy K.; Fulton, Christopher E.; May, Ryan D.; Owen, A. Karl

2012-01-01

This paper describes the implementation and evaluation of a yaw rate to throttle feedback system designed to replace a damaged rudder. It can act as a Dutch roll damper and as a means to facilitate pilot input for crosswind landings. Enhanced propulsion control modes were implemented to increase responsiveness and thrust level of the engine, which impact flight dynamics and performance. Piloted evaluations were performed to determine the capability of the engines to substitute for the rudder function under emergency conditions. The results showed that this type of implementation is beneficial, but the engines' capability to replace the rudder is limited.

Nuclear reactor steam depressurization valve

International Nuclear Information System (INIS)

Moore, G.L.

1991-01-01

This patent describes improvement in a nuclear reactor plant, an improved steam depressurization valve positioned intermediate along a steam discharge pipe for controlling the venting of steam pressure from the reactor through the pipe. The improvement comprises: a housing including a domed cover forming a chamber and having a partition plate dividing the chamber into a fluid pressure activation compartment and a steam flow control compartment, the valve housing being provided with an inlet connection and an outlet connection in the steam flow control compartment, and a fluid duct in communication with a source of fluid pressure for operating the valve; a valve set mounted within the fluid flow control compartment comprising a cylindrical section surrounding the inlet connection with one end adjoining the connection and having a radially projecting flange at the other end with a contoured extended valve sealing flange provided with an annular valve sealing member, and a valve cylinder traversing the partition plate and reciprocally movable within an opening in the partition plate with one terminal and extending into the fluid pressure activation compartment and the other terminal end extending into the steam flow control compartment coaxially aligned with the valve seat surrounding the inlet connection, the valve cylinder being surrounded by two bellow fluid seals and provided with guides to inhibit lateral movement, an end of the valve cylinder extending into the fluid flow control compartment having a radially projecting flange substantially conterminous with the valve seat flange and having a contoured surface facing and complimentary to the contoured valve seating surface whereby the two contoured valve surfaces can meet in matching relationship, thus providing a pressure actuated reciprocatable valve member for making closing contact with the valve seat and withdrawing therefrom for opening fluid flow through the valve

Redo mitral valve surgery

Directory of Open Access Journals (Sweden)

Redoy Ranjan

2018-03-01

Full Text Available This study is based on the findings of a single surgeon’s practice of mitral valve replacement of 167 patients from April 2005 to June 2017 who developed symptomatic mitral restenosis after closed or open mitral commisurotomy. Both clinical and color doppler echocardiographic data of peri-operative and six months follow-up period were evaluated and compared to assess the early outcome of the redo mitral valve surgery. With male-female ratio of 1: 2.2 and after a duration of 6 to 22 years symptom free interval between the redo procedures, the selected patients with mitral valve restenosis undergone valve replacement with either mechanical valve in 62% cases and also tissue valve in 38% cases. Particular emphasis was given to separate the adhered pericardium from the heart completely to ameliorate base to apex and global contraction of the heart. Besides favorable post-operative clinical outcome, the echocardiographic findings were also encouraging as there was statistically significant increase in the mitral valve area and ejection fraction with significant decrease in the left atrial diameter, pressure gradient across the mitral valve and pulmonary artery systolic pressure. Therefore, in case of inevitable mitral restenosis after closed or open commisurotomy, mitral valve replacement is a promising treatment modality.

Double-disc gate valve

International Nuclear Information System (INIS)

Wheatley, S.J.

1979-01-01

The invention relates to an improvement in a conventional double-disc gate valve having a vertically movable gate assembly including a wedge, spreaders slidably engaged therewith, a valve disc carried by the spreaders. When the gate assembly is lowered to a selected point in the valve casing, the valve discs are moved transversely outward to close inlet and outlet ports in the casing. The valve includes hold-down means for guiding the disc-and-spreader assemblies as they are moved transversely outward and inward. If such valves are operated at relatively high differential pressures, they sometimes jam during opening. Such jamming has been a problem for many years in gate valves used in gaseous diffusion plants for the separation of uranium isotopes. The invention is based on the finding that the above-mentioned jamming results when the outlet disc tilts about its horizontal axis in a certain way during opening of the valve. In accordance with the invention, tilting of the outlet disc is maintained at a tolerable value by providing the disc with a rigid downwardly extending member and by providing the casing with a stop for limiting inward arcuate movement of the member to a preselected value during opening of the valve

Intro to Valve Guide Reconditioning. Automotive Mechanics. Valves. Instructor's Guide [and] Student Guide.

Science.gov (United States)

Horner, W.

This instructional package, one in a series of individualized instructional units on tools and techniques for repairing worn valve guides in motor vehicles, provides practical experience for students in working on cylinder heads. Covered in the module are reaming valve guides that are oversized to match a new oversized valve, reaming valve guides…

Guide to prosthetic cardiac valves

International Nuclear Information System (INIS)

Morse, D.; Steiner, R.M.; Fernandez, J.

1985-01-01

This book contains 10 chapters. Some of the chapter titles are: The development of artificial heart valves: Introduction and historical perspective; The radiology of prosthetic heart valves; The evaluation of patients for prosthetic valve implantation; Pathology of cardiac valve replacement; and Bioengineering of mechanical and biological heart valve substitutes

Trans-apical aortic valve implantation in a patient with stentless valve degeneration.

Science.gov (United States)

Kapetanakis, Emmanouil I; MacCarthy, Philip; Monaghan, Mark; Wendler, Olaf

2011-06-01

Trans-apical valve-in-valve trans-catheter aortic valve implantation (TAVI) has successfully been performed in selected, high-risk patients, who suffered prosthetic degeneration after aortic valve replacement using stented xenografts. We report the case of a 79-year-old male patient who underwent one of the first successful TAVIs in a failing stentless bioprosthesis. Copyright © 2010 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved.

Early clinical outcome of aortic transcatheter valve-in-valve implantation in the Nordic countries

DEFF Research Database (Denmark)

Ihlberg, Leo; Nissen, Henrik Hoffmann; Nielsen, Niels Erik

2013-01-01

Transcatheter valve-in-valve implantation has emerged as an option, in addition to reoperative surgical aortic valve replacement, to treat failed biologic heart valve substitutes. However, the clinical experience with this approach is still limited. We report the comprehensive experience...

Nuclear valves latest development

International Nuclear Information System (INIS)

Isaac, F.; Monier, M.

1993-01-01

In the frame of Nuclear Power Plant upgrade (Emergency Power Supply and Emergency Core Cooling), Westinghouse had to face a new valve design philosophy specially for motor operated valves. The valves have to been designed to resist any operating conditions, postulated accident or loss of control. The requirements for motor operated valves are listed and the selected model and related upgrading explained. As part of plant upgrade and valves replacement, Westinghouse has sponsored alternative hardfacing research programme. Two types of materials have been investigated: nickel base alloys and iron base alloys. Programme requirements and test results are given. A new globe valve model (On-Off or regulating) is described developed by Alsthom Velan permitting the seat replacement in less than 10 min. (Z.S.) 2 figs

Magnetic Check Valve

Science.gov (United States)

Morris, Brian G.; Bozeman, Richard J., Jr.

1994-01-01

Poppet in proposed check valve restored to closed condition by magnetic attraction instead of spring force. Oscillations suppressed, with consequent reduction of wear. Stationary magnetic disk mounted just upstream of poppet, also containing magnet. Valve body nonmagnetic. Forward pressure or flow would push poppet away from stationary magnetic disk so fluid flows easily around poppet. Stop in valve body prevents poppet from being swept away. When flow stopped or started to reverse, magnetic attraction draws poppet back to disk. Poppet then engages floating O-ring, thereby closing valve and preventing reverse flow. Floating O-ring facilitates sealing at low loads.

Studies for the requirements of automatic and remotely controlled shutoff valves on hazardous liquids and natural gas pipelines with respect to public and environmental safety

Energy Technology Data Exchange (ETDEWEB)

Oland, C. Barry [XCEL Engineering, Inc. (United States); Rose, Simon D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Engineering Science and Technology Div.; Grant, Herb L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Fabrication, Hoisting and Rigging Div.; Lower, Mark D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Fabrication, Hoisting and Rigging Div.; Spann, Mark A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Facility Management Div.; Kirkpatrick, John R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Computational Sciences and Engineering Div.; Sulfredge, C. David [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Computational Sciences and Engineering Div.

2012-12-01

This study assesses the effectiveness of block valve closure swiftness in mitigating the consequences of natural gas and hazardous liquid pipeline releases on public and environmental safety. It also evaluates the technical, operational, and economic feasibility and potential cost benefits of installing automatic shutoff valves (ASVs) and remote control valves (RCVs) in newly constructed and fully replaced transmission lines. Risk analyses of hypothetical pipeline release scenarios are used as the basis for assessing: (1) fire damage to buildings and property in Class 1, Class 2, Class 3, and Class 4 high consequence areas (HCAs) caused by natural gas pipeline releases and subsequent ignition of the released natural gas; (2) fire damage to buildings and property in HCAs designated as high population areas and other populated areas caused by hazardous liquid pipeline releases and subsequent ignition of the released propane; and (3) socioeconomic and environmental damage in HCAs caused by hazardous liquid pipeline releases of crude oil. These risk analyses use engineering principles and fire science practices to characterize thermal radiation effects on buildings and humans and to quantify the total damage cost of socioeconomic and environmental impacts. The risk analysis approach used for natural gas pipelines is consistent with risk assessment standards developed by industry and incorporated into Federal pipeline safety regulations. Feasibility evaluations for the hypothetical pipeline release scenarios considered in this study show that installation of ASVs and RCVs in newly constructed and fully replaced natural gas and hazardous liquid pipelines is technically, operationally, and economically feasible with a positive cost benefit. However, these results may not apply to all newly constructed and fully replaced pipelines because site-specific parameters that influence risk analyses and feasibility evaluations often vary significantly from one pipeline segment to

Anterior mitral valve aneurysm: a rare sequelae of aortic valve endocarditis

Directory of Open Access Journals (Sweden)

Rajesh Janardhanan

2016-05-01

Full Text Available In intravenous drug abusers, infective endocarditis usually involves right-sided valves, with Staphylococcus aureus being the most common etiologic agent. We present a patient who is an intravenous drug abuser with left-sided (aortic valve endocarditis caused by Enterococcus faecalis who subsequently developed an anterior mitral valve aneurysm, which is an exceedingly rare complication. A systematic literature search was conducted which identified only five reported cases in the literature of mitral valve aneurysmal rupture in the setting of E. faecalis endocarditis. Real-time 3D-transesophageal echocardiography was critical in making an accurate diagnosis leading to timely intervention. Learning objectives: • Early recognition of a mitral valve aneurysm (MVA is important because it may rupture and produce catastrophic mitral regurgitation (MR in an already seriously ill patient requiring emergency surgery, or it may be overlooked at the time of aortic valve replacement (AVR. • Real-time 3D-transesophageal echocardiography (RT-3DTEE is much more advanced and accurate than transthoracic echocardiography for the diagnosis and management of MVA.

Anterior mitral valve aneurysm: a rare sequelae of aortic valve endocarditis.

Science.gov (United States)

Janardhanan, Rajesh; Kamal, Muhammad Umar; Riaz, Irbaz Bin; Smith, M Cristy

2016-03-01

SummaryIn intravenous drug abusers, infective endocarditis usually involves right-sided valves, with Staphylococcus aureus being the most common etiologic agent. We present a patient who is an intravenous drug abuser with left-sided (aortic valve) endocarditis caused by Enterococcus faecalis who subsequently developed an anterior mitral valve aneurysm, which is an exceedingly rare complication. A systematic literature search was conducted which identified only five reported cases in the literature of mitral valve aneurysmal rupture in the setting of E. faecalis endocarditis. Real-time 3D-transesophageal echocardiography was critical in making an accurate diagnosis leading to timely intervention. Early recognition of a mitral valve aneurysm (MVA) is important because it may rupture and produce catastrophic mitral regurgitation (MR) in an already seriously ill patient requiring emergency surgery, or it may be overlooked at the time of aortic valve replacement (AVR).Real-time 3D-transesophageal echocardiography (RT-3DTEE) is much more advanced and accurate than transthoracic echocardiography for the diagnosis and management of MVA. © 2016 The authors.

Transcatheter Aortic Valve Replacement for Degenerative Bioprosthetic Surgical Valves

DEFF Research Database (Denmark)

Dvir, Danny; Webb, John; Brecker, Stephen

2012-01-01

Transcatheter aortic valve-in-valve implantation is an emerging therapeutic alternative for patients with a failed surgical bioprosthesis and may obviate the need for reoperation. We evaluated the clinical results of this technique using a large, worldwide registry....

Transcatheter aortic valve replacement

Science.gov (United States)

... gov/ency/article/007684.htm Transcatheter aortic valve replacement To use the sharing features on this page, please enable JavaScript. Transcatheter aortic valve replacement (TAVR) is surgery to replace the aortic valve. ...

Overflow control valve

International Nuclear Information System (INIS)

Kessinger, B.A.; Hundal, R.; Parlak, E.A.

1982-01-01

An overflow control valve for use in a liquid sodium coolant pump tank which can be remotely engaged with and disengaged from the pump tank wall to thereby permit valve removal. An actuating shaft for controlling the valve also has means for operating a sliding cylinder against a spring to retract the cylinder from sealing contact with the pump tank nozzle. (author)

The prognosis of infective endocarditis treated with biological valves versus mechanical valves: A meta-analysis.

Science.gov (United States)

Tao, Ende; Wan, Li; Wang, WenJun; Luo, YunLong; Zeng, JinFu; Wu, Xia

2017-01-01

Surgery remains the primary form of treatment for infective endocarditis (IE). However, it is not clear what type of prosthetic valve provides a better prognosis. We conducted a meta-analysis to compare the prognosis of infective endocarditis treated with biological valves to cases treated with mechanical valves. Pubmed, Embase and Cochrane databases were searched from January 1960 to November 2016.Randomized controlled trials, retrospective cohorts and prospective studies comparing outcomes between biological valve and mechanical valve management for infective endocarditis were analyzed. The Newcastle-Ottawa Scale(NOS) was used to evaluate the quality of the literature and extracted data, and Stata 12.0 software was used for the meta-analysis. A total of 11 publications were included; 10,754 cases were selected, involving 6776 cases of biological valves and 3,978 cases of mechanical valves. The all-cause mortality risk of the biological valve group was higher than that of the mechanical valve group (HR = 1.22, 95% CI 1.03 to 1.44, P = 0.023), as was early mortality (RR = 1.21, 95% CI 1.02 to 1.43, P = 0.033). The recurrence of endocarditis (HR = 1.75, 95% CI 1.26 to 2.42, P = 0.001), as well as the risk of reoperation (HR = 1.79, 95% CI 1.15 to 2.80, P = 0.010) were more likely to occur in the biological valve group. The incidence of postoperative embolism was less in the biological valve group than in the mechanical valve group, but this difference was not statistically significant (RR = 0.90, 95% CI 0.76 to 1.07, P = 0.245). For patients with prosthetic valve endocarditis (PVE), there was no significant difference in survival rates between the biological valve group and the mechanical valve group (HR = 0.91, 95% CI 0.68 to 1.21, P = 0.520). The results of our meta-analysis suggest that mechanical valves can provide a significantly better prognosis in patients with infective endocarditis. There were significant differences in the clinical features of patients

Method of effecting fast turbine valving for improvement of power system stability

International Nuclear Information System (INIS)

Park, R.H.

1981-01-01

As a improved way of effecting fast valving of turbines of power system steam-electric generating units for the purpose of improving the stability of power transmission over transmission circuits to which their generators make connection, when stability is threatened by line faults and certain other stability endangering events, the heretofore employed and/or advocated practice of automatically closing intercept valves at fastest available closing speed in response to a fast valving signal, and thereafter automatically fully reopening them in a matter of seconds, is modified by providing to reopen the valves only partially to and thereafter retain them at a preset partially open position. For best results the process of what can be termed sustained partial reopening is so effected as to result in its completion within a fraction of a second following the peak of the first forward swing of the generator rotor. Control valves may be either held open, or automatically fully or partly closed and thereafter fully opened in a preprogrammed manner, or automatically moved to and thereafter held in a partly closed position, by means of a preprogrammed process of repositioning in which the valves may optionally be first fully or partly closed and thereafter partly reopened. Avoidance of discharge of steam through high pressure safety valves can be had with use of suitably controlled power operated valves that discharge steam to the condenser or to atmosphere. Where there is an intermediate pressure turbine that is supplied with superheated steam, use of sustained partial control valve closure, if employed, is supplemented by provision for reduction of rate of heat release within the steam generator in order to protect the reheater from overheating. As a way to restrict increase of reheat pressure of fossil fuel installations, and to minimize increase in the msr (Moisture separator-reheater) pressure of nuclear units, provision is optionally made of normally closed by-pass v

Comparative study of Butterfly valves

International Nuclear Information System (INIS)

Galmes Belmonte, F.B.

1998-01-01

This work tries to justify the hydrodynamic butterfly valves performance, using the EPRI tests, results carried out in laboratory and in situ. This justification will be possible if: - The valves to study are similar - Their performance is calculated using EPRI's methodology Looking for this objective, the elements of the present work are: 1. Brief EPRI butterfly valve description it wild provide the factors which are necessary to define the butterfly valves similarity. 2. EPRI tests description and range of validation against test data definition. 3. Description of the spanish butterfly analyzed valves, and comparison with the EPRI performance results, to prove that this valves are similar to the EPRI test valves. In this way, it will not be necessary to carry out particular dynamic tests on the spanish valves to describe their hydrodynamic performance. (Author)

Fluid mechanics of heart valves.

Science.gov (United States)

Yoganathan, Ajit P; He, Zhaoming; Casey Jones, S

2004-01-01

Valvular heart disease is a life-threatening disease that afflicts millions of people worldwide and leads to approximately 250,000 valve repairs and/or replacements each year. Malfunction of a native valve impairs its efficient fluid mechanic/hemodynamic performance. Artificial heart valves have been used since 1960 to replace diseased native valves and have saved millions of lives. Unfortunately, despite four decades of use, these devices are less than ideal and lead to many complications. Many of these complications/problems are directly related to the fluid mechanics associated with the various mechanical and bioprosthetic valve designs. This review focuses on the state-of-the-art experimental and computational fluid mechanics of native and prosthetic heart valves in current clinical use. The fluid dynamic performance characteristics of caged-ball, tilting-disc, bileaflet mechanical valves and porcine and pericardial stented and nonstented bioprostheic valves are reviewed. Other issues related to heart valve performance, such as biomaterials, solid mechanics, tissue mechanics, and durability, are not addressed in this review.

Intelligent Flow Control Valve

Science.gov (United States)

Kelley, Anthony R (Inventor)

2015-01-01

The present invention is an intelligent flow control valve which may be inserted into the flow coming out of a pipe and activated to provide a method to stop, measure, and meter flow coming from the open or possibly broken pipe. The intelligent flow control valve may be used to stop the flow while repairs are made. Once repairs have been made, the valve may be removed or used as a control valve to meter the amount of flow from inside the pipe. With the addition of instrumentation, the valve may also be used as a variable area flow meter and flow controller programmed based upon flowing conditions. With robotic additions, the valve may be configured to crawl into a desired pipe location, anchor itself, and activate flow control or metering remotely.

Effect of co-free valve on activity reduction in PWR

International Nuclear Information System (INIS)

Bahn, C.B.; Han, B.C.; Bum, J.S.; Hwang, I.S.; Lee, C.B.

2002-01-01

Radioactive nuclei, such as 68 Co and 60 Co, deposited on out-of-core surfaces in a pressurized water reactor (PWR) primary coolant system, are major sources of occupational radiation exposure to plant maintenance personnel and act as costly impediment to prompt and effective repairs. Valve hardfacing alloys exposed to primary coolant are considered as one of the main Co sources. To evaluate the Co-free valve, such as NOREM 02 and Deloro 50, the candidates for the alternative to Stellite 6, in a simulated PWR primary condition, SNU corrosion test loop (SCOTL) was constructed. For gate valves hard-faced with made of NOREM 02 and Deloro 50 hot cycling tests were conducted for up to 2,000 on-off cycles with cold leak tests at 1,000 cycle interval. It was observed that the leak rate of NOREM 02 (Fe-base) did not satisfy the nuclear grade valve leak criteria. After 1000 cycles test, while there was no leakage in case of Deloro 50 (Ni-base). Also, Deloro 50 showed no leakage after 2000 cycles. To estimate the activity reduction effect, we modified CRUDSIM-MIT which modeled the effects of coolant chemistry on the crud transport and activity buildup in the primary system of PWR. In the new code, crud evaluation and assessment (CREAT), 60 Co activity buildup prediction includes 1) Co-base valve replacement effect, 2) Co-base valve maintenance effect, and 3) control rod drive mechanism (CRDM) and main coolant pump (MCP) shaft contribution. CREAT predicted that the main contributor of Co activity buildup was the corrosion-induced release of Co from the steam generator (SG) tubing. With new SG's tubed with alloy 690, Korean Next Generation Reactor (APR-1400) is expected to have about 64% lower Co activity on SG surface. The use of all Co-free valves is expected to cut additional 8% of activity which is only marginal. (authors)

Experience with valves for PHWR reactors

International Nuclear Information System (INIS)

Narayan, K.; Mhetre, S.G.

1977-01-01

Material specifications and inspection and testing requirements of the valves meant for use in nuclear reactors are mentioned. In the heavy water systems (both primary and moderator) of a PHWR type reactor, the valves used are gate valves, globe valves, diaphragm valves, butterfly valves, check valves and relief valves. Their locations and functions they perform in the Rajasthan Atomic Power Station Unit-1 are described. Experience with them is given. The major problems encountered with them have been : (1) leakage from the stem seals and body bonnet joint, (2) leakage due to failure of diaphragm and/or washout of the packing and (3) malfunctioning. Measures taken to solve these are discussed. Finally a mention has been made of improved versions of valves, namely, metal diaphragm valve and inverted relief valve. (M.G.B.)

Leaving Moderate Tricuspid Valve Regurgitation Alone at the Time of Pulmonary Valve Replacement: A Worthwhile Approach.

Science.gov (United States)

Kogon, Brian; Mori, Makoto; Alsoufi, Bahaaldin; Kanter, Kirk; Oster, Matt

2015-06-01

Pulmonary valve disruption in patients with tetralogy of Fallot and congenital pulmonary stenosis often results in pulmonary insufficiency, right ventricular dilation, and tricuspid valve regurgitation. Management of functional tricuspid regurgitation at the time of subsequent pulmonary valve replacement remains controversial. Our aims were to (1) analyze tricuspid valve function after pulmonary valve replacement through midterm follow-up and (2) determine the benefits, if any, of concomitant tricuspid annuloplasty. Thirty-five patients with tetralogy of Fallot or congenital pulmonary stenosis were analyzed. All patients had been palliated in childhood by disrupting the pulmonary valve, and all patients had at least moderate tricuspid valve regurgitation at the time of subsequent pulmonary valve replacement. Preoperative and serial postoperative echocardiograms were analyzed. Pulmonary and tricuspid regurgitation, along with right ventricular dilation and dysfunction were scored as 0 (none), 1 (mild), 2 (moderate), and 3 (severe). Right ventricular volume and area were also calculated. Comparisons were made between patients who underwent pulmonary valve replacement alone and those who underwent concomitant tricuspid valve annuloplasty. At 1 month after pulmonary valve replacement, there were significant reductions in pulmonary valve regurgitation (mean 3 vs 0.39, p tricuspid valve regurgitation (mean 2.33 vs 1.3, p tricuspid regurgitation 1 month postoperatively between patients who underwent concomitant tricuspid annuloplasty and those who underwent pulmonary valve replacement alone (mean 1.31 vs 1.29, p = 0.81). However, at latest follow-up (mean 7.0 ± 2.8 years), the degree of tricuspid regurgitation was significantly higher in the concomitant annuloplasty group (mean 1.87 vs 1.12, p = 0.005). In patients with at least moderate tricuspid valve regurgitation, significant improvement in tricuspid valve function and right ventricular size occurs in the first

The Double-Orifice Valve Technique to Treat Tricuspid Valve Incompetence.

Science.gov (United States)

Hetzer, Roland; Javier, Mariano; Delmo Walter, Eva Maria

2016-01-01

A straightforward tricuspid valve (TV) repair technique was used to treat either moderate or severe functional (normal valve with dilated annulus) or for primary/organic (Ebstein's anomaly, leaflet retraction/tethering and chordal malposition/tethering, with annular dilatation) TV incompetence, and its long-term outcome assessed. A double-orifice valve technique was employed in 91 patients (mean age 52.6 ± 23.2 years; median age 56 years; range: 0.6-82 years) with severe tricuspid regurgitation. Among the patients, three had post-transplant iatrogenic chordal rupture, five had infective endocarditis, 11 had mitral valve insufficiency, 23 had Ebstein's anomaly, and 47 had isolated severe TV incompetence. The basic principle was to reduce the distance between the coapting leaflets, wherein the most mobile leaflet could coapt to the opposite leaflet, by creating two orifices, ensuring valve competence. The TV repair was performed through a median sternotomy or right anterior thoracotomy in the fifth intercostal space under cardiopulmonary bypass. The degree and extent of creating a double-valve orifice was determined by considering the minimal body surface area (BSA)-related acceptable TV diameter. Repair was accomplished by passing pledgeted mattress sutures from the middle of the true anterior annulus to a spot on the opposite septal annulus, located approximately two-thirds of the length of the septal annulus to avoid injury to the bundle of His. The annular apposition divides the TV into a larger anterior and a smaller posterior orifices, enabling valve closure, on both sides. In adults, the diameter of the anterior valve orifice should be 23-25 mm, and the posterior orifice 15-18 mm; thus, the total valve orifice area is 5-6 cm2. In children, the total valve orifice should be a standard deviation of 1.7 mm for a BSA of 1.0m2. During a mean follow up of 8.7 ± 1.34 years (median 10 years; range: 1.5-25.9 years) there have been no reoperations for TV insufficiency

Percutaneous aortic valve implantation of the Medtronic CoreValve self-expanding valve prosthesis via left subclavian artery access: the first case report in Greece.

Science.gov (United States)

Karavolias, George K; Georgiadou, Panagiota; Houri, Mazen; Sbarouni, Eftihia; Thomopoulou, Sofia; Tsiapras, Dimitrios; Smirli, Anna; Balanika, Marina; Voudris, Vassilis

2010-01-01

This case report describes a percutaneous aortic valve implantation with the Medtronic CoreValve selfexpanding valve prosthesis in a patient with severe aortic stenosis. The approach was made via the left subclavian artery because of the lack of femoral vessel access. The patient was a 78-year-old female with breathlessness on minimal effort, a recent hospitalisation due to pulmonary oedema, and frequent episodes of pre-syncope; surgical valve replacement had been ruled out. The prosthetic valve was successfully implanted with mild paravalvular aortic regurgitation. At 30 days, the patient's clinical condition had significantly improved, with excellent functioning of the aortic valve prosthesis.

Flow oscillations on the steam control valve in the middle opening condition. Clarification of the effects of valve body and valve seat by steam experiments

International Nuclear Information System (INIS)

Morita, Ryo; Inada, Fumio

2007-01-01

A steam control valve might cause vibrations of piping when the valve opening is in a middle condition. For rationalization of maintenance and management of the plant, the valve should be improved, but it is difficult to understand flow characteristics in detail by experiment because flow around the valve is complex 3D structure and becomes supersonic (M>1). Therefore, it is necessary to clarify the cause of the vibrations and to develop the countermeasures by CFD (Computational Fluid Dynamics) technology. In previous researches, we clarified a mechanism of the pressure fluctuations in the middle opening condition and suggested the new valve shape (named 'Extended Valve') that can suppress the pressure fluctuations by air experiments and CFD calculations. Then, we also conducted steam experiments and CFD calculations to understand the differences between air and the steam, and found that the pressure fluctuations in the middle opening condition also occurred in the steam tests and the differences between the air and steam were not remarkable. In this report, to clarify the effects of valve and valve seat shape in steam flow condition, we conduct the steam experiments with various valve and seat shape. As a result, we find the change of the valve seat can decrease the amplitude of pressure fluctuations, but can not quite suppress the pressure fluctuations in the middle opening condition. Then, we apply the 'Extended Valve' to clarify the valve shape effect, and find that the extended valve suppresses the pressure fluctuations in the middle opening condition completely and decreases the pressure amplitude drastically. (author)

Development of Flight Safety Prediction Methodology for U. S. Naval Safety Center. Revision 1

Science.gov (United States)

1970-02-01

INLET? 133410 AADM3 A 76 Clit.. VALVE-ANJTI SIN 11341$ AARHLE A 79 HYU PILTEN 113410) AABHF A Ito6 TU1i1111 11341s AAAuo A ivi, wbrULAT10OI * CONTROL...SWITCH323AA4 LOARBA A NO HYU XFER PUMP CONTROL RELAY323AA* LBARbB A AFTERBURNER MODE SELECT 3 LBARC L LOARS AAAAAAAAA 3 LBARC KAH PI THROTTLE LEVER 329311...RESERVOIR Z4512A KOCA A 54. BLELD VALVE Zb12$ KDOB A 55 HYU /FUEL RADIATOR Z45128 KDDC A 56 FILTLR 245127 KDOO 357 RESERVOIR CHECK VALVE Z�* KODE Ab8 PUMP

Effects of the blockage ratio of a valve disk on loss coefficient in a butterfly valve

International Nuclear Information System (INIS)

Rho, Hyung Joon; Lee, Jee Keun; Choi, Hee Joo

2008-01-01

The loss coefficient of the butterfly valve which allows partial opening of the valve at closed position and is applicable to the small-sized pipe system with the diameter of 1 inch was measured for the variation of the valve disk blockage ratio. Two different types of the valve disk configuration to adjust the blockage ratio were considered. One was the solid type valve disk of which the diameter was changed into the smaller size rather than the pipe diameter, and the other was the perforate type valve disk on which some holes were perforated. The results from two types of valve disk were compared to identify their characteristics in the loss coefficient distributions. The loss coefficient and the controllable angle of the valve disk were decreased exponentially with the decrease of the blockage ratio. In addition, the perforate valve disk had the effect on the higher loss coefficient rather than the solid type valve disk

Characterization of a bioprosthetic bicuspid venous valve hemodynamics: implications for mechanism of valve dynamics.

Science.gov (United States)

Tien, W-H; Chen, H Y; Berwick, Z C; Krieger, J; Chambers, S; Dabiri, D; Kassab, G S

2014-10-01

Chronic venous insufficiency (CVI) of the lower extremities is a common clinical problem. Although bioprosthetic valves have been proposed to treat severe reflux, clinical success has been limited due to thrombosis and neointima overgrowth of the leaflets that is, in part, related to the hemodynamics of the valve. A bioprosthetic valve that mimics native valve hemodynamics is essential. A computational model of the prosthetic valve based on realistic geometry and mechanical properties was developed to simulate the interaction of valve structure (fluid-structure interaction, FSI) with the surrounding flow. The simulation results were validated by experiments of a bioprosthetic bicuspid venous valve using particle image velocimetry (PIV) with high spatial and temporal resolution in a pulse duplicator (PD). Flow velocity fields surrounding the valve leaflets were calculated from PIV measurements and comparisons to the FSI simulation results were made. Both the spatial and temporal results of the simulations and experiments were in agreement. The FSI prediction of the transition point from equilibrium phase to valve-closing phase had a 7% delay compared to the PD measurements, while the PIV measurements matched the PD exactly. FSI predictions of reversed flow were within 10% compared to PD measurements. Stagnation or stasis regions were observed in both simulations and experiments. The pressure differential across the valve and associated forces on the leaflets from simulations showed the valve mechanism to be pressure driven. The flow velocity simulations were highly consistent with the experimental results. The FSI simulation and force analysis showed that the valve closure mechanism is pressure driven under the test conditions. FSI simulation and PIV measurements demonstrated that the flow behind the leaflet was mostly stagnant and a potential source for thrombosis. The validated FSI simulations should enable future valve design optimizations that are needed for

Cryogenic Cam Butterfly Valve

Science.gov (United States)

McCormack, Kenneth J. (Inventor)

2016-01-01

A cryogenic cam butterfly valve has a body that includes an axially extending fluid conduit formed there through. A disc lug is connected to a back side of a valve disc and has a circular bore that receives and is larger than a cam of a cam shaft. The valve disc is rotatable for a quarter turn within the body about a lug axis that is offset from the shaft axis. Actuating the cam shaft in the closing rotational direction first causes the camming side of the cam of the cam shaft to rotate the disc lug and the valve disc a quarter turn from the open position to the closed position. Further actuating causes the camming side of the cam shaft to translate the valve disc into sealed contact with the valve seat. Opening rotational direction of the cam shaft reverses these motions.

Temperature control for liquid-helium cryostats below 4.2 K

International Nuclear Information System (INIS)

Escorne, M.; Mauger, A.

1983-01-01

We report the operational characteristics of a membrane type of manostat and of a throttle valve system which we have constructed to regulate the pressure P above the liquid-helium bath. The choice of the manostat rather than the other device depends on the nature of the experiments to be performed: in the membrane type of manostat, the temperature is determined with an accuracy limited by the fluctuations ΔT around the mean value T. With throttle valves, the accuracy is limited by the drift of T in time. The performance of both devices prove to be sufficiently good as they stand, since the departure from T in the course of the experiments is lower than 10 -2 K in the whole range 1.4< T<4.2 K, being well inside this limit below 2 K. The need for expensive and complex electronic regulations to improve the temperature control is thus exceptional

Dual source heat pump

Science.gov (United States)

Ecker, Amir L.; Pietsch, Joseph A.

1982-01-01

What is disclosed is a heat pump apparatus for conditioning a fluid characterized by a fluid handler and path for circulating the fluid in heat exchange relationship with a refrigerant fluid; at least two refrigerant heat exchangers, one for effecting heat exchange with the fluid and a second for effecting heat exchange between refrigerant and a heat exchange fluid and the ambient air; a compressor for efficiently compressing the refrigerant; at least one throttling valve for throttling liquid refrigerant; a refrigerant circuit; refrigerant; a source of heat exchange fluid; heat exchange fluid circulating device and heat exchange fluid circuit for circulating the heat exchange fluid in heat exchange relationship with the refrigerant; and valves or switches for selecting the heat exchangers and direction of flow of the refrigerant therethrough for selecting a particular mode of operation. The heat exchange fluid provides energy for defrosting the second heat exchanger when operating in the air source mode and also provides a alternate source of heat.

Small valve area index: its influence on early mortality after mitral valve replacement

NARCIS (Netherlands)

Yazdanbakhsh, A. P.; van den Brink, R. B.; Dekker, Egbert; de Mol, B. A.

2000-01-01

OBJECTIVE: To test the hypothesis that mitral valve prosthesis-patient mismatch increases postoperative mortality. METHODS AND RESULTS: The effect of mitral valve prosthesis-patient mismatch on survival in a cohort of consecutive patients after mitral valve replacement with a mechanical prosthesis

Björk-Shiley convexoconcave valves: susceptibility artifacts at brain MR imaging and mechanical valve fractures.

Science.gov (United States)

van Gorp, Maarten J; van der Graaf, Yolanda; de Mol, Bas A J M; Bakker, Chris J G; Witkamp, Theo D; Ramos, Lino M P; Mali, Willem P T M

2004-03-01

To assess the relationship between heart valve history and susceptibility artifacts at magnetic resonance (MR) imaging of the brain in patients with Björk-Shiley convexoconcave (BSCC) valves. MR images of the brain were obtained in 58 patients with prosthetic heart valves: 20 patients had BSCC valve replacements, and 38 had other types of heart valves. Two experienced neuroradiologists determined the presence or absence of susceptibility artifacts in a consensus reading. Artifacts were defined as characteristic black spots that were visible on T2*-weighted gradient-echo MR images. The statuses of the 20 explanted BSCC valves-specifically, whether they were intact or had an outlet strut fracture (OSF) or a single-leg fracture (SLF)-had been determined earlier. Number of artifacts seen at brain MR imaging was correlated with explanted valve status, and differences were analyzed with nonparametric statistical tests. Significantly more patients with BSCC valves (17 [85%] of 20 patients) than patients with other types of prosthetic valves (18 [47%] of 38 patients) had susceptibility artifacts at MR imaging (P =.005). BSCC valve OSFs were associated with a significantly higher number of artifacts than were intact BSCC valves (P =.01). No significant relationship between SLF and number of artifacts was observed. Susceptibility artifacts at brain MR imaging are not restricted to patients with BSCC valves. These artifacts can be seen on images obtained in patients with various other types of fractured and intact prosthetic heart valves. Copyright RSNA, 2004

Low noise control valve

International Nuclear Information System (INIS)

Christie, R.S.

1975-01-01

Noise is one of the problems associated with the use of any type of control valve in systems involving the flow of fluids. The advent of OSHA standards has prompted control valve manufacturers to design valves with special trim to lower the sound pressure level to meet these standards. However, these levels are in some cases too high, particularly when a valve must be located in or near an area where people are working at tasks requiring a high degree of concentration. Such locations are found around and near research devices and in laboratory-office areas. This paper describes a type of fluid control device presently being used at PPL as a bypass control valve in deionized water systems and designed to reduce sound pressure levels considerably below OSHA standards. Details of the design and construction of this constant pressure drop variable flow control valve are contained in the text and are shown in photographs and drawings. Test data taken are included

Idiopathic mitral valve prolapse with tricuspid, aortic and pulmonary valve involvement: An autopsy case report

Directory of Open Access Journals (Sweden)

Heena M Desai

2015-01-01

Full Text Available Mitral valve prolapse (MVP is usually asymptomatic, but can be associated with complications such as infective endocarditis, mitral regurgitation, thromboembolism and sudden cardiac death. It has been very rarely reported to occur in association with other valvular involvement. A 55-year-old male patient was brought dead and at autopsy the mitral valve orifice was stenotic and the leaflets were enlarged, myxoid and bulging suggestive of MVP and chordae tendinae were thickened, stretched and elongated. Similar changes were seen in the tricuspid valve. The pulmonary and aortic valves also showed myxomatous degeneration of their cusps. Myxomatous degeneration is the most common cause of MVP and it can be associated with involvement of the other valves. Concomitant involvement of the aortic valve has been reported, however it is very rare and simultaneous involvement of the pulmonary valve has not been reported in the literature so far. We report a case of MVP associated with myxomatous degeneration of the tricuspid, pulmonary and aortic valves.

A remotely operated drug delivery system with an electrolytic pump and a thermo-responsive valve

KAUST Repository

Yi, Ying; Zaher, Amir; Yassine, Omar; Kosel, Jü rgen; Foulds, Ian G.

2015-01-01

Implantable drug delivery devices are becoming attractive due to their abilities of targeted and controlled dose release. Currently, two important issues are functional lifetime and non-controlled drug diffusion. In this work, we present a drug delivery device combining an electrolytic pump and a thermo-responsive valve, which are both remotely controlled by an electromagnetic field (40.5 mT and 450 kHz). Our proposed device exhibits a novel operation mechanism for long-term therapeutic treatments using a solid drug in reservoir approach. Our device also prevents undesired drug liquid diffusions. When the electromagnetic field is on, the electrolysis-induced bubble drives the drug liquid towards the Poly (N-Isopropylacrylamide) (PNIPAM) valve that consists of PNIPAM and iron micro-particles. The heat generated by the iron micro-particles causes the PNIPAM to shrink, resulting in an open valve. When the electromagnetic field is turned off, the PNIPAM starts to swell. In the meantime, the bubbles are catalytically recombined into water, reducing the pressure inside the pumping chamber, which leads to the refilling of the fresh liquid from outside the device. A catalytic reformer is included, allowing more liquid refilling during the limited valve's closing time. The amount of body liquid that refills the drug reservoir can further dissolve the solid drug, forming a reproducible drug solution for the next dose. By repeatedly turning on and off the electromagnetic field, the drug dose can be cyclically released, and the exit port of the device is effectively controlled.

Valve for closing a steam line

International Nuclear Information System (INIS)

Meyer, W.; Potrykus, G.

1976-01-01

Instead of several control elements, the quick-closing valve, especially in the main-steam line between steam generator and turbine of a power station has the valve cone itself as the only movable part, acting with its inner surface as a piston within a second cylinder space. The valve shaft is at the same time a piston rod with a stepped piston at the upper end. This piston is loaded in a cylinder at the upspace below the valve cover on one hand by a spring, on the other hand by its own medium. Two non-return valves, one of it in a bore of the valve cone, connect the first-mentioned cylinder space with the steam-loaded inlet resp. outlet side of the valve. For controlling the valve, a magnet valve is sufficient. By automatic control of the valve cone coupled with several pistons several control lines can be omitted. There are also no pressurized control lines outside the valve which could be damaged by exterior influences. (ERA) [de

Malfunction of a Heimlich flutter valve causing tension pneumothorax: case report of a rare complication

Directory of Open Access Journals (Sweden)

Braunstein Volker A

2010-06-01

Full Text Available Abstract Background Thoracic injuries play an important role in major trauma patients due to their high incidence and critical relevance. A serious consequence of thoracic trauma is pneumothorax, a condition that quickly can become life-threatening and requires immediate treatment. Decompression is the state of the art for treating tension pneumothorax. There are many different methods of decompression using different techniques, devices, valves and drainage systems. Referring to our case report we would like to discuss the utilization of these devices. Case presentation We report of a patient suffering from tension pneumothorax despite insertion of a chest drain at the accident scene. The decompression was by tube thoracostomy which was connected to a Heimlich flutter valve. During air transportation the patient suffered from cardiorespiratory arrest with asystole and was admitted to the trauma room undergoing manual chest compressions. The initial chest film showed a persisting tension pneumothorax, despite the chest tube that had been correctly placed and connected properly to the Heimlich valve. We assume that the Heimlich valve leaves did not open up and thus tension pneumothorax was not released. Conclusion We would like to raise awareness to the fact that if a Heimlich flutter valve is applied in the pre-hospital setting it should be used with caution. Failure in this type of valve may lead to recurrent tension pneumothorax.

Ultrasonic leak detection

International Nuclear Information System (INIS)

Murphy, R.V.

1977-01-01

A scanning ultrasonic microphone was used to detect the presence and locate the sources of hydraulic noises in piping systems in a reactor environment. The intensity changes of the noises correspond to changes of flow conditions within the system caused by throttled valves, flow rate changes, and leaks. (author)

Rates of fuel discharge as affected by the design of fuel-injection systems for internal-combustion engines

Science.gov (United States)

Gelalles, A G; Marsh, E T

1933-01-01

Using the method of weighing fuel collected in a receiver during a definite interval of the injection period, rates of discharge were determined, and the effects noted, when various changes were made in a fuel-injection system. The injection system consisted primarily of a by-pass controlled fuel pump and an automatic injection valve. The variables of the system studied were the pump speed, pump-throttle setting, discharge-orifice diameter, injection-valve opening and closing pressures, and injection-tube length and diameter.

Door valve for fuel handling path

International Nuclear Information System (INIS)

Makishima, Katsuhiko.

1969-01-01

A door valve is provided which seals cover gas from a liquid metal cooled reactor without leakage therefrom. A threaded shaft is screwed into a heavy box press which is packed with lead. The shaft is adapted to be rotated by an electric motor or a manually operated wheel which is disposed outside of the door valve. From the box press a valve plate is suspended by four linkage bars, one for each corner. Each linkage bar is provided with two wheels which are respectively mounted at the connections with the box press and the valve plate. The wheels are carried on the horizontal grooves formed in a door valve casing. In operation the shaft rotates and travels to permit the box press and the valve plate to move into the door valve casing while the valve plate does not contact the casing. When the box press reaches the home position, the wheels drop into the recesses which are disposed at the ends of the grooves, the valve plate is carried on the valve opening, and the box press presses the valve plate to increase the tightness. The valve plate does not suffer wear as it does not over other parts. (Yamaguchi, T.)

Impact of bicuspid aortic valve on complications and death in infective endocarditis of native aortic valves.

Science.gov (United States)

Kahveci, Gokhan; Bayrak, Fatih; Pala, Selcuk; Mutlu, Bulent

2009-01-01

We retrospectively investigated the impact of bicuspid aortic valve on the prognosis of patients who had definite infective endocarditis of the native aortic valve.Of 51 patients, a bicuspid aortic valve was present in 22 (43%); the other 29 had tricuspid aortic valves. On average, the patients who had bicuspid valves were younger than those who had tricuspid valves. Patients with a tricuspid valve had larger left atrial diameters and were more likely to have severe mitral regurgitation.Periannular complications, which we detected in 19 patients (37%), were much more common in the patients who had a bicuspid valve (64% vs 17%, P = 0.001). The presence of a bicuspid valve was the only significant independent predictor of periannular complications. The in-hospital mortality rate in the bicuspid group was lower than that in the tricuspid group; however, this figure did not reach statistical significance (9% vs 24%, P = 0.15). In multivariate analysis, left atrial diameter was the only independent predictor associated with an increased risk of death (hazard ratio, 2.19; 95% confidence interval, 1.1-4.5; P = 0.031).In our study, patients with infective endocarditis in a bicuspid aortic valve were younger and had a higher incidence of periannular complications. Although a worse prognosis has been reported previously, we found that infective endocarditis in a native bicuspid aortic valve is not likely to increase the risk of death in comparison with infective endocarditis in native tricuspid aortic valves.

Gate valve performance prediction

International Nuclear Information System (INIS)

Harrison, D.H.; Damerell, P.S.; Wang, J.K.; Kalsi, M.S.; Wolfe, K.J.

1994-01-01

The Electric Power Research Institute is carrying out a program to improve the performance prediction methods for motor-operated valves. As part of this program, an analytical method to predict the stem thrust required to stroke a gate valve has been developed and has been assessed against data from gate valve tests. The method accounts for the loads applied to the disc by fluid flow and for the detailed mechanical interaction of the stem, disc, guides, and seats. To support development of the method, two separate-effects test programs were carried out. One test program determined friction coefficients for contacts between gate valve parts by using material specimens in controlled environments. The other test program investigated the interaction of the stem, disc, guides, and seat using a special fixture with full-sized gate valve parts. The method has been assessed against flow-loop and in-plant test data. These tests include valve sizes from 3 to 18 in. and cover a considerable range of flow, temperature, and differential pressure. Stem thrust predictions for the method bound measured results. In some cases, the bounding predictions are substantially higher than the stem loads required for valve operation, as a result of the bounding nature of the friction coefficients in the method

Mitral Valve Prolapse

Science.gov (United States)

... valve syndrome . What happens during MVP? Watch an animation of mitral valve prolapse When the heart pumps ( ... our brochures Popular Articles 1 Understanding Blood Pressure Readings 2 Sodium and Salt 3 Heart Attack Symptoms ...

Application of ceramics to the sliding seat of valve bridge; Valve bridge yodobu eno ceramics tekiyo

Energy Technology Data Exchange (ETDEWEB)

Matsui, T; Ono, T [Mitsubishi Motors Corp., Tokyo (Japan)

1997-10-01

For use in the valve train, using an OHV (over head valve) configuration. of a 4 valve diesel engine for trucks and buses; we developed a valve bridge, a component of a valve train, with a ceramic head that is made of silicon nitride(Si3N4) in contact with a rocker arm in order to reduce cost and improve wear resistance for further diesel engine emissions regulations. In order to evaluate the effect of this valve bridge, RIG tests and durability tests on actual engines were carried out. 7 figs., 2 tabs.

Transcatheter Mitral Valve-in-Ring Implantation

LENUS (Irish Health Repository)

Tanner, RE

2018-05-01

Failed surgical mitral valve repair using an annuloplasty ring has traditionally been treated with surgical valve replacement or repair1. For patients at high risk for repeat open heart surgery, placement of a trans-catheter aortic valve (i.e., TAVI valve) within the mitral ring (i.e., Mitral-Valve-in-Ring, MViR) has emerged as a novel alternative treatment strategy2-5 . We describe our experience of a failed mitral valve repair that was successfully treated with a TAVI valve delivered via the trans-septal approach, and summarise the data relating to this emerging treatment strategy.

A new one-step procedure for pulmonary valve implantation of the melody valve: Simultaneous prestenting and valve implantation.

Science.gov (United States)

Boudjemline, Younes

2018-01-01

To describe a new modification, the one-step procedure, that allows interventionists to pre-stent and implant a Melody valve simultaneously. Percutaneous pulmonary valve implantation (PPVI) is the standard of care for managing patients with dysfunctional right ventricular outflow tract, and the approach is standardized. Patients undergoing PPVI using the one-step procedure were identified in our database. Procedural data and radiation exposure were compared to those in a matched group of patients who underwent PPVI using the conventional two-step procedure. Between January 2016 and January 2017, PPVI was performed in 27 patients (median age/range, 19.1/10-55 years) using the one-step procedure involving manual crimping of one to three bare metal stents over the Melody valve. The stent and Melody valve were delivered successfully using the Ensemble delivery system. No complications occurred. All patients had excellent hemodynamic results (median/range post-PPVI right ventricular to pulmonary artery gradient, 9/0-20 mmHg). Valve function was excellent. Median procedural and fluoroscopic times were 56 and 10.2 min, respectively, which significantly differed from those of the two-step procedure group. Similarly, the dose area product (DAP), and radiation time were statistically lower in the one-step group than in the two-step group (P step procedure is a safe modification that allows interventionists to prestent and implants the Melody valve simultaneously. It significantly reduces procedural and fluoroscopic times, and radiation exposure. © 2017 Wiley Periodicals, Inc.

Space Vehicle Valve System

Science.gov (United States)

Kelley, Anthony R. (Inventor); Lindner, Jeffrey L. (Inventor)

2014-01-01

The present invention is a space vehicle valve system which controls the internal pressure of a space vehicle and the flow rate of purged gases at a given internal pressure and aperture site. A plurality of quasi-unique variable dimension peaked valve structures cover the purge apertures on a space vehicle. Interchangeable sheet guards configured to cover valve apertures on the peaked valve structure contain a pressure-activated surface on the inner surface. Sheet guards move outwardly from the peaked valve structure when in structural contact with a purge gas stream flowing through the apertures on the space vehicle. Changing the properties of the sheet guards changes the response of the sheet guards at a given internal pressure, providing control of the flow rate at a given aperture site.

Transcatheter valve-in-valve implantation due to severe aortic regurgitation in a degenerated aortic homograft

DEFF Research Database (Denmark)

Olsen, Lene Kjaer; Engstrøm, Thomas; Søndergaard, Lars

2009-01-01

Transcatheter aortic valve implantation (TAVI) in severe aortic stenosis has proven to be a feasible and effective treatment modality for inoperable patients. Until now, neither aortic regurgitation nor degenerated bioprostheses has been an indication for TAVI. However, this article reports...... a successful valve-in-valve implantation of a CoreValve aortic valve prosthesis through the right subclavian artery in a case of severe aortic regurgitation within a degenerated aortic homograft. The case exemplifies the possibilities of expanding the indications for TAVI, as well as other vascular access...

Thermally induced pressure locking of gate valves: A survey of valve bonnet pressurization rates

International Nuclear Information System (INIS)

Ezekoye, L.I.; Moore, W.E.

1996-01-01

Closed, water filled gate valves run the risk of becoming pressurized due to heat input from the environment or from adjacent connected piping. Thermal pressurization of gate valve bonnets may lead to the valves failing to open on demand and can even induce structural failure of valves. This paper presents an analytical prediction of the pressurization rate of a closed pressure vessel subject to uniform heating which may be considered as an upper bound to the pressurization rate that may occur in the field. Then actual valve experiences described in the literature are reviewed to determine the expected pressurization rate in existing hardware designs. A statistical approach is applied to reconcile the differing pressurization rates reported in the literature and determine a rate that can be applied in valve evaluations. The limitations of the reconciled rate are discussed

Colombian experience with transcatheter aortic valve implantation of medtronic CoreValve.

Science.gov (United States)

Dager, Antonio E; Nuis, Rutger-Jan; Caicedo, Bernardo; Fonseca, Jaime A; Arana, Camilo; Cruz, Lidsa; Benitez, Luis M; Nader, Carlos A; Duenas, Eduardo; de Marchena, Eduardo J; O'Neill, William W; de Jaegere, Peter P

2012-01-01

At our institutions, increasing numbers of aortic stenosis patients were not candidates for surgical aortic valve replacement. Accordingly, we initiated the Cali Colombian Transcatheter Aortic Valve Implantation (TAVI) program. From March 2008 through January 2011, 53 consecutive patients (mean age, 79 ± 6 yr; men, 58%) underwent TAVI with the Medtronic CoreValve System, and data were prospectively collected. Our study's endpoints conformed with Valve Academic Research Consortium recommendations. We report our clinical results.Predicted mortality rates were 25% (interquartile range, 17%-34%) according to logistic EuroSCORE and 6% (interquartile range, 3%-8%) according to the Society of Thoracic Surgeons score. The 30-day mortality rate was 9% (3 intraprocedural deaths, 5 total). The combined 30-day safety endpoint was 30% (major vascular sequelae, 23%; life-threatening bleeding, 12%; myocardial infarction, 4%; major stroke, 4%; and acute kidney injury [stage 3], 2%). Eight patients (15%) required post-implantation balloon dilation and 2 (4%) required valve-in-valve implantation, for a technical device success rate of 77%. Mean peak transvalvular gradient decreased from 74 ± 29 to 17 ± 8 mmHg and mean transvalvular gradient from 40 ± 17 to 8 ± 4 mmHg (both P=0.001). Moderate or severe aortic regurgitation decreased from 32% to 18% (P=0.12) and mitral regurgitation from 32% to 13% (P=0.002). The 1-year survival rate was 81%.We found that TAVI with the CoreValve prosthesis was safe and feasible, with sustained long-term results, for treating aortic stenosis in patients at excessive surgical risk; nonetheless, serious adverse events occurred in 30% of the patients.

Traumatic Mitral Valve and Pericardial Injury

Directory of Open Access Journals (Sweden)

Nissar Shaikh

2013-01-01

Full Text Available Cardiac injury after blunt trauma is common but underreported. Common cardiac trauma after the blunt chest injury (BCI is cardiac contusion; it is very rare to have cardiac valve injury. The mitral valve injury during chest trauma occurs when extreme pressure is applied at early systole during the isovolumic contraction between the closure of the mitral valve and the opening of the aortic valve. Traumatic mitral valve injury can involve valve leaflet, chordae tendineae, or papillary muscles. For the diagnosis of mitral valve injury, a high index of suspicion is required, as in polytrauma patients, other obvious severe injuries will divert the attention of the treating physician. Clinical picture of patients with mitral valve injury may vary from none to cardiogenic shock. The echocardiogram is the main diagnostic modality of mitral valve injuries. Patient’s clinical condition will dictate the timing and type of surgery or medical therapy. We report a case of mitral valve and pericardial injury in a polytrauma patient, successfully treated in our intensive care unit.

Mechanisms of mechanical heart valve cavitation: investigation using a tilting disk valve model.

Science.gov (United States)

He, Z; Xi, B; Zhu, K; Hwang, N H

2001-09-01

The induction of mechanical heart valve (MHV) cavitation was investigated using a 27 mm Medtronic Hall (MH27) tilting disk valve. The MH27 valve was mounted in the mitral position of a simulating pulse flow system, and stroboscopic lighting used to visualize cavitation bubbles on the occluder inflow surface at the instant of valve closure. MHV cavitation was monitored using a digital camera with 0.04 mm/pixel resolution sufficient to render the tiny bubbles clearly visible on the computer monitor screen. Cavitation on MH27 valve was classified as five types according to the time, site and shape of the cavitation bubbles. Valve cavitation occurred at the instant of occluder impact with the valve seat at closing. The impact motion was subdivided into three temporal phases: (i) squeezing flow; (ii) elastic collision; and (iii) leaflet rebound. MHV cavitation caused by vortices was found to be initiated by the squeezing jet and/or by the transvalvular leakage jets. By using a tension wave which swept across the occluder surface immediately upon elastic impact, nuclei in the vortex core were expanded to form cavitation bubbles. Analysis of the shape and location of the cavitation bubbles permitted a better understanding of MHV cavitation mechanisms, based on the fluid dynamics of jet vortex and tension wave propagations.

Fairchild Stratos Division's Type II prototype lockhopper valve: METC Prototype Test Valve No. F-1 prototype lockhopper valve-testing and development project. Static test report

Energy Technology Data Exchange (ETDEWEB)

Goff, D. R.; Cutright, R. L.; Griffith, R. A.; Loomis, R. B.; Maxfield, D. A.; Moritz, R. S.

1981-10-01

METC Prototype Test Valve No. F-1 is a hybrid design, based on a segmented ball termed a visor valve, developed and manufactured by Fairchild Stratos Division under contract to the Department of Energy. The valve uses a visor arm that rotates into position and then translates to seal. This valve conditionally completed static testing at METC with clean gas to pressures of 1600 psig and internal valve temperatures to 600/sup 0/F. External leakage was excessive due to leakage through the stuffing box, purge fittings, external bolts, and other assemblies. The stuffing box was repacked several times and redesigned midway through the testing, but external leakage was still excessive. Internal leakage through the seats, except for a few anomalies, was very low throughout the 2409 cycles of testing. As shown by the low internal leakage, the visor valve concept appears to have potential for lock-hopper valve applications. The problems that are present with METC Prototype Test Valve No. F-1 are in the seals, which are equivalent to the shaft and bonnet seals in standard valve designs. The operating conditions at these seals are well within the capabilities of available seal designs and materials. Further engineering and minor modifications should be able to resolve the problems identified during static testing.

Design And Analysis Of A Camless Valve Mechanism For I.C Engines Using Rotary Disc Valves

Directory of Open Access Journals (Sweden)

Vivek Jitendra Panchal

2017-09-01

Full Text Available It is the object of the presented paper to provide an electromechanical rotary valve actuating system for opening and closing valves of an internal combustion engine capable of separately controlling both the inlet and exhaust valve operations of each individual cylinder in a multi-cylinder engine. This indicates that only one valve will be required for each cylinder of the engine. Previously published versions of this concept require a separate valve for intake and exhaust in each cylinder. The system provides an alternative to the camshaft assembly in an attempt to overcome the limitations and inadequacies inevitably posed by a fully mechanical system. The prototype development is approached in a theoretical manner beginning with the conceptualization and design of a rotating disk with a notches and corresponding closure surfaces to open and close the flow path. The actuated disk and notch design is then refined and followed by the design of an inlet and exhaust manifold to correspond to the valve design and the theorizing and design of a sealing gasket. The rotating speed of the valve is determined by a general idling speed and can be varied to provide variable valve timing with the motor. The final assembly eliminates a majority of the moving parts currently used in camshaft systems like the cam camshaft rocker arm push rod and springs and results in a significantly lighter valve actuation system. By eliminating the translatory motion of valves the problem of valves slamming on the valve seats at high velocities is eliminated thus greatly reducing engine wear.

Refrigerant flow through electronic expansion valve: Experiment and neural network modeling

International Nuclear Information System (INIS)

Cao, Xiang; Li, Ze-Yu; Shao, Liang-Liang; Zhang, Chun-Lu

2016-01-01

Highlights: • Experimental data from different sources were used in comparison of EEV models. • Artificial neural network in EEV modeling is superior to literature correlations. • Artificial neural network with 4-4-1 structure and S function is recommended. • Artificial neural network is flexible for EEV mass flow rate and opening prediction. - Abstract: Electronic expansion valve (EEV) plays a crucial role in controlling refrigerant mass flow rate of refrigeration or heat pump systems for energy savings. However, complexities in two-phase throttling process and geometry make accurate modeling of EEV flow characteristics more difficult. This paper developed an artificial neural network (ANN) model using refrigerant inlet and outlet pressures, inlet subcooling, EEV opening as ANN inputs, refrigerant mass flow rate as ANN output. Both linear and nonlinear transfer functions in hidden layer were used and compared to each other. Experimental data from multiple sources including in-house experiments of one EEV with R410A were used for ANN training and test. In addition, literature correlations were compared with ANN as well. Results showed that the ANN model with nonlinear transfer function worked well in all cases and it is much accurate than the literature correlations. In all cases, nonlinear ANN predicted refrigerant mass flow rates within ±0.4% average relative deviation (A.D.) and 2.7% standard deviation (S.D.), meanwhile it predicted the EEV opening at 0.1% A.D. and 2.1% S.D.

Simulant Development for Hanford Tank Farms Double Valve Isolation (DVI) Valves Testing

Energy Technology Data Exchange (ETDEWEB)

Wells, Beric E.

2012-12-21

Leakage testing of a representative sample of the safety-significant isolation valves for Double Valve Isolation (DVI) in an environment that simulates the abrasive characteristics of the Hanford Tank Farms Waste Transfer System during waste feed delivery to the Waste Treatment and Immobilization Plant (WTP) is to be conducted. The testing will consist of periodic leak performed on the DVI valves after prescribed numbers of valve cycles (open and close) in a simulated environment representative of the abrasive properties of the waste and the Waste Transfer System. The valve operations include exposure to cycling conditions that include gravity drain and flush operation following slurry transfer. The simulant test will establish the performance characteristics and verify compliance with the Documented Safety Analysis. Proper simulant development is essential to ensure that the critical process streams characteristics are represented, National Research Council report “Advice on the Department of Energy's Cleanup Technology Roadmap: Gaps and Bridges”

Stent valve implantation in conventional redo aortic valve surgery to prevent patient-prosthesis mismatch.

Science.gov (United States)

Ferrari, Enrico; Franciosi, Giorgio; Clivio, Sara; Faletra, Francesco; Moccetti, Marco; Moccetti, Tiziano; Pedrazzini, Giovanni; Demertzis, Stefanos

2017-03-01

The goal was to show the technical details, feasibility and clinical results of balloon-expandable stent valve implantation in the aortic position during conventional redo open-heart surgery in selected obese patients with a small aortic prosthesis and severe patient-prosthesis mismatch. Two symptomatic overweight patients (body mass index of 31 and 38), each with a small aortic prosthesis (a 4-year-old, 21-mm Hancock II biological valve and a 29-year-old, 23-mm Duromedic mechanical valve), increased transvalvular gradients (59/31 and 74/44 mmHg) and a reduced indexed effective orifice area (0.50 and 0.43 cm 2 /m 2 ) underwent implantation of two 26-mm balloon-expandable Sapien 3 valves during standard on-pump redo valve surgery. Using full re-sternotomy, cardiopulmonary bypass and cardioplegic arrest, the two balloon-expandable stent valves were implanted under direct view using a standard aortotomy, after prosthesis removal and without annulus enlargement. Aortic cross-clamp times were 162 and 126 min; cardiopulmonary bypass times were 178 and 180 min; total surgical times were 360 and 318 min. At discharge, echocardiograms showed transvalvular peak and mean gradients of 13/9 and 23/13 mmHg and indexed effective orifice areas of 0.64 and 1.08 cm 2 /m 2 . The 3-month echocardiographic follow-up showed transvalvular peak and mean gradients of 18/9 and 19/11 mmHg and indexed effective orifice areas of 0.78 cm 2 /m 2 and 0.84 cm 2 /m 2 , with improved symptoms (New York Heart Association class 1). Implantation of a balloon-expandable stent valve during redo aortic valve surgery is feasible in selected cases and prevents patient-prosthesis mismatch in obese patients without need for aortic annulus enlargement. Moreover, in the case of stent valve degeneration, this approach permits additional valve-in-valve procedures with large stent valves and prevents re-redo surgery. © The Author 2016. Published by Oxford University Press on behalf of the

Cyclonic valve test: preliminary results

Energy Technology Data Exchange (ETDEWEB)

Monteiro, Andre Sampaio; Moraes, Carlos Alberto C.; Marins, Luiz Philipe M.; Soares, Fabricio; Oliveira, Dennis; Lima, Fabio Soares de; Airao, Vinicius [Petroleo Brasileiro S.A. (PETROBRAS), Rio de Janeiro, RJ (Brazil); Ton, Tijmen [Twister BV, Rijswijk (Netherlands)

2012-07-01

For many years, the petroleum industry has been developing a valve that input less shear to the flow for a given required pressure drop and this can be done using the cyclonic concept. This paper presents a comparison between the performances of a cyclonic valve (low shear) and a conventional globe valve. The aim of this work is to show the advantages of using a cyclonic low shear valve instead of the commonly used in the primary separation process by PETROBRAS. Tests were performed at PETROBRAS Experimental Center (NUEX) in Aracaju/SE varying some parameters: water cut; pressure loss (from 4 kgf/cm2 to 10 kgf/cm2); flow rates (30 m3/h and 45 m3/h). Results indicates a better performance of the cyclonic valve, if compared with a conventional one, and also that the difference of the performance, is a function of several parameters (emulsion stability, water content free, and oil properties). The cyclonic valve tested can be applied as a choke valve, as a valve between separation stages (for pressure drop), or for controlling the level of vessels. We must emphasize the importance to avoid the high shear imposed by conventional valves, because once the emulsion is created, it becomes more difficult to break it. New tests are being planned to occur in 2012, but PETROBRAS is also analyzing real cases where the applications could increase the primary process efficiency. In the same way, the future installations are also being designed considering the cyclonic valve usage. (author)

Bioprinting a cardiac valve.

Science.gov (United States)

Jana, Soumen; Lerman, Amir

2015-12-01

Heart valve tissue engineering could be a possible solution for the limitations of mechanical and biological prostheses, which are commonly used for heart valve replacement. In tissue engineering, cells are seeded into a 3-dimensional platform, termed the scaffold, to make the engineered tissue construct. However, mimicking the mechanical and spatial heterogeneity of a heart valve structure in a fabricated scaffold with uniform cell distribution is daunting when approached conventionally. Bioprinting is an emerging technique that can produce biological products containing matrix and cells, together or separately with morphological, structural and mechanical diversity. This advance increases the possibility of fabricating the structure of a heart valve in vitro and using it as a functional tissue construct for implantation. This review describes the use of bioprinting technology in heart valve tissue engineering. Copyright © 2015 Elsevier Inc. All rights reserved.

Diseases of the Tricuspid Valve

Science.gov (United States)

... stenosis. Tricuspid Regurgitation Tricuspid regurgitation is also called tricuspid insufficiency or tricuspid incompetence. It means there is a ... require valve surgery. Tags: heart valves , tricuspid incompetence , ... tricuspid regurgitation , tricuspid stenosis , valve disease Related Links ...

Optimal results of aortic valve replacement with small mechanical valves (< 19 mm).

Science.gov (United States)

Kato, Yasuyuki; Hattori, Koji; Motoki, Manabu; Takahashi, Yosuke; Kotani, Shinsuke; Nishimura, Shinsuke; Shibata, Toshihiko

2013-07-01

Controversy exists regarding the optimal operative method or type of prosthesis for patients with a small aortic root. The aim of this retrospective study was to investigate the early and mid-term outcomes of standard aortic valve replacement (AVR) using 16 mm or 18 mm ATS Advanced Performance (AP) or 17 mm St. Jude Medical (SJM) Regent valves for a small aortic root. Between April 2003 and August 2009, 78 patients (age range: 50-86 years; 86% aged > or = 65 years) underwent AVR with 16 mm or 18 mm ATS AP valves (16AP group: n = 21, 18AP group: n = 32), or a 17 mm SJM Regent valve (17Regent group: n = 25). Fifty-six patients (72%) had a body surface area (BSA) of regression was similar among the groups (-30%, -25% and -28% in the 16AP, 17Regent and 18AP groups, respectively; p = 0.844). The early and mid-term results of AVR with 16 mm or 18 mm ATS AP valves, or with a 17 mm SJM Regent valve, were satisfactory. Therefore, standard AVR using these small mechanical prostheses, which avoids the need to enlarge the annulus or to conduct stentless bioprosthesis implantation, might represent an acceptable method, especially in elderly patients with a small aortic root.

Transcatheter mitral valve repair in osteogenesis imperfecta associated mitral valve regurgitation.

Science.gov (United States)

van der Kley, Frank; Delgado, Victoria; Ajmone Marsan, Nina; Schalij, Martin J

2014-08-01

Osteogenesis imperfecta is associated with increased prevalence of significant mitral valve regurgitation. Surgical mitral valve repair and replacement are feasible but are associated with increased risk of bleeding and dehiscence of implanted valves may occur more frequently. The present case report describes the outcomes of transcatheter mitral valve repair in a patient with osteogenesis imperfecta. A 60 year-old patient with osteogenesis imperfecta and associated symptomatic moderate to severe mitral regurgitation underwent transthoracic echocardiography which showed a nondilated left ventricle with preserved systolic function and moderate to severe mitral regurgitation. On transoesophageal echocardiography the regurgitant jet originated between the anterolateral scallops of the anterior and posterior leaflets (A1-P1). Considering the comorbidities associated with osteogenesis imperfecta the patient was accepted for transcatheter mitral valve repair using the Mitraclip device (Abbott vascular, Menlo, CA). Under fluoroscopy and 3D transoesophageal echocardiography guidance, a Mitraclip device was implanted between the anterolateral and central scallops with significant reduction of mitral regurgitation. The postoperative evolution was uneventful. At one month follow-up, transthoracic echocardiography showed a stable position of the Mitraclip device with no mitral regurgitation. Transcatheter mitral valve repair is feasible and safe in patients with osteogenesis imperfecta and associated symptomatic significant mitral regurgitation. Copyright © 2014 Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) and the Cardiac Society of Australia and New Zealand (CSANZ). Published by Elsevier B.V. All rights reserved.

Development of an effective valve packing program

Energy Technology Data Exchange (ETDEWEB)

Hart, K.A.

1996-12-01

Current data now shows that graphite valve packing installed within the guidance of a controlled program produces not only reliable stem sealing but predictable running loads. By utilizing recent technological developments in valve performance monitoring for both MOV`s and AOV`s, valve packing performance can be enhanced while reducing maintenance costs. Once known, values are established for acceptable valve packing loads, the measurement of actual valve running loads via the current MOV/AOV diagnostic techniques can provide indication of future valve stem sealing problems, improper valve packing installation or identify the opportunity for valve packing program improvements. At times the full benefit of these advances in material and predictive technology remain under utilized due to simple past misconceptions associated with valve packing. This paper will explore the basis for these misconceptions, provide general insight into the current understanding of valve packing and demonstrate how with this new understanding and current valve diagnostic equipment the key aspects required to develop an effective, quality valve packing program fit together. The cost and operational benefits provided by this approach can be significant impact by the: elimination of periodic valve repacking, reduction of maintenance costs, benefits of leak-free valve operation, justification for reduced Post Maintenance Test Requirements, reduced radiation exposure, improved plant appearance.

Inverse spin-valve effect in nanoscale Si-based spin-valve devices

Science.gov (United States)

Hiep, Duong Dinh; Tanaka, Masaaki; Hai, Pham Nam

2017-12-01

We investigated the spin-valve effect in nano-scale silicon (Si)-based spin-valve devices using a Fe/MgO/Ge spin injector/detector deposited on Si by molecular beam epitaxy. For a device with a 20 nm Si channel, we observed clear magnetoresistance up to 3% at low temperature when a magnetic field was applied in the film plane along the Si channel transport direction. A large spin-dependent output voltage of 20 mV was observed at a bias voltage of 0.9 V at 15 K, which is among the highest values in lateral spin-valve devices reported so far. Furthermore, we observed that the sign of the spin-valve effect is reversed at low temperatures, suggesting the possibility of a spin-blockade effect of defect states in the MgO/Ge tunneling barrier.

Mechanical versus bioprosthetic aortic valve replacement.

Science.gov (United States)

Head, Stuart J; Çelik, Mevlüt; Kappetein, A Pieter

2017-07-21

Mechanical valves used for aortic valve replacement (AVR) continue to be associated with bleeding risks because of anticoagulation therapy, while bioprosthetic valves are at risk of structural valve deterioration requiring reoperation. This risk/benefit ratio of mechanical and bioprosthetic valves has led American and European guidelines on valvular heart disease to be consistent in recommending the use of mechanical prostheses in patients younger than 60 years of age. Despite these recommendations, the use of bioprosthetic valves has significantly increased over the last decades in all age groups. A systematic review of manuscripts applying propensity-matching or multivariable analysis to compare the usage of mechanical vs. bioprosthetic valves found either similar outcomes between the two types of valves or favourable outcomes with mechanical prostheses, particularly in younger patients. The risk/benefit ratio and choice of valves will be impacted by developments in valve designs, anticoagulation therapy, reducing the required international normalized ratio, and transcatheter and minimally invasive procedures. However, there is currently no evidence to support lowering the age threshold for implanting a bioprosthesis. Physicians in the Heart Team and patients should be cautious in pursuing more bioprosthetic valve use until its benefit is clearly proven in middle-aged patients. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2017. For permissions, please email: journals.permissions@oup.com.

Latest design of gate valves

Energy Technology Data Exchange (ETDEWEB)

Kurzhofer, U.; Stolte, J.; Weyand, M.

1996-12-01

Babcock Sempell, one of the most important valve manufacturers in Europe, has delivered valves for the nuclear power industry since the beginning of the peaceful application of nuclear power in the 1960s. The latest innovation by Babcock Sempell is a gate valve that meets all recent technical requirements of the nuclear power technology. At the moment in the United States, Germany, Sweden, and many other countries, motor-operated gate and globe valves are judged very critically. Besides the absolute control of the so-called {open_quotes}trip failure,{close_quotes} the integrity of all valve parts submitted to operational forces must be maintained. In case of failure of the limit and torque switches, all valve designs have been tested with respect to the quality of guidance of the gate. The guidances (i.e., guides) shall avoid a tilting of the gate during the closing procedure. The gate valve newly designed by Babcock Sempell fulfills all these characteristic criteria. In addition, the valve has cobalt-free seat hardfacing, the suitability of which has been proven by friction tests as well as full-scale blowdown tests at the GAP of Siemens in Karlstein, West Germany. Babcock Sempell was to deliver more than 30 gate valves of this type for 5 Swedish nuclear power stations by autumn 1995. In the presentation, the author will report on the testing performed, qualifications, and sizing criteria which led to the new technical design.

Thermal fatigue behavior of valves

International Nuclear Information System (INIS)

Moinereau, D.; Scliffet, L.; Capion, J.C.; Genette, P.

1991-01-01

This paper reports that valves of pressurized water reactors are exposed to thermal shocks during transient operations. The numerous thermal shock tests performed on valves on the EDF test facilities have shown the sensibility of fillets and geometrical discontinuities to thermal fatigue: cracks can appear in those areas and grow through the valve body. Valves systems designated as level 1 must be designed to withstand fatigue up to the second isolation valve: the relevant rule is specified in the paragraph B 3500 of the French RCCM code. It is a simplified method which doesn't require finite element calculations. Many valve systems have been designed according to this rule and have been operated without accident. However, in one case, important cracks were found in the fillet of a check-valve after numerous thermal shocks. Calculation of the valve's behavior according to the RCCM code to estimate the fatigue damage resulting from thermal shocks led to a low damage factor, which doesn't agree with the experimental results. This was confirmed by new testings and showed the inadequacy of B 3500 rule for thermal transients. On this base a new rule is proposed to estimate fatigue damage resulting from thermal shocks. An experimental program has been realized to validate this rule. Axisymetrical analytical mock-ups with different geometries and one check-valve in austenitic stainless steel 316 L have been submitted to hot thermal shocks of 210 degrees C magnitude

Surge-damping vacuum valve

International Nuclear Information System (INIS)

Bullock, J.C.; Kelley, B.E.

1977-01-01

A valve for damping out flow surges in a vacuum system is described. The surge-damping mechanism consists of a slotted, spring-loaded disk adjacent to the valve's vacuum port (the flow passage to the vacuum roughing pump). Under flow surge conditions, the differential pressure forces the disk into a sealing engagement with the vacuum port, thereby restricting the gas flow path to narrow slots in the disk's periphery. The increased flow damps out the flow surge. When pressure is equalized on both sides of the valve, the spring load moves the disk away from the port to restore full flow conductance through the valve

Depth of valve implantation, conduction disturbances and pacemaker implantation with CoreValve and CoreValve Accutrak system for Transcatheter Aortic Valve Implantation, a multi-center study.

Science.gov (United States)

Lenders, Guy D; Collas, Valérie; Hernandez, José Maria; Legrand, Victor; Danenberg, Haim D; den Heijer, Peter; Rodrigus, Inez E; Paelinck, Bernard P; Vrints, Christiaan J; Bosmans, Johan M

2014-10-20

Transcatheter Aortic Valve Implantation (TAVI) is now considered an indispensable treatment strategy in high operative risk patients with severe, symptomatic aortic stenosis. However, conduction disturbances and the need for Permanent Pacemaker (PPM) implantation after TAVI with the CoreValve prosthesis still remain frequent. We aimed to evaluate the implantation depth, the incidence and predictors of new conduction disturbances, and the need for PPM implantation within the first month after TAVI, using the new Accutrak CoreValve delivery system (ACV), compared to the previous generation CoreValve (non-ACV). In 5 experienced TAVI-centers, a total of 120 consecutive non-ACV and 112 consecutive ACV patients were included (n=232). The mean depth of valve implantation (DVI) was 8.4±4.0 mm in the non-ACV group and 7.1±4.0 mm in the ACV group (p=0.034). The combined incidence of new PPM implantation and new LBBB was 71.2% in the non-ACV group compared to 50.5% in the ACV group (p=0.014). DVI (p=0.002), first degree AV block (p=0.018) and RBBB (p<0.001) were independent predictors of PPM implantation. DVI (p<0.001) and pre-existing first degree AV-block (p=0.021) were identified as significant predictors of new LBBB. DVI is an independent predictor of TAVI-related conduction disturbances and can be reduced by using the newer CoreValve Accutrak delivery system, resulting in a significantly lower incidence of new LBBB and new PPM implantation. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Characteristic analysis of servo valve

International Nuclear Information System (INIS)

Ko, J. H.; Ryu, D. R.; Lee, J. H.; Kim, Y. S.; Na, J. C.; Kim, D. S.

2008-01-01

Electro-pneumatic servo valve is an electro-mechanical device which converts electric signals into a proper pneumatic flow rate or pressure. In order to improve the overall performance of pneumatic servo systems, electro-pneumatic servo valves are required, which have fast dynamic characteristics, no air leakage at a null point, and can be fabricated at a low-cost. The first objective of this research is to design and to fabricate a new electro-pneumatic servo valve which satisfies the above-mentioned requirements. In order to design the mechanism of the servo valve optimally, the flow inside the valve depending upon the position of spool was analyzed variously, and on the basis of such analysis results, the valve mechanism, which was formed by combination of the spool and the sleeve, was designed and manufactured. And a tester for conducting an overall performance test was designed and manufactured, and as a result of conducting the flow rate test, the pressure test and the frequency test on the developed pneumatic servo valve

Small sodium valve design and operating experience

International Nuclear Information System (INIS)

Abramson, R.; Elie, X.; Vercasson, M.; Nedelec, J.

1974-01-01

Conventionally, valves for sodium pipes smaller than 125 mm in diameter are called ''small sodium valves''. However, this limit should rather be considered as the lower limit o ''large sodium valves''. In fact, both the largest sizes of small valves and the smallest of large valves can be found in the range of 125-300 mm in diameter. Thus what is said about small valves also applies, for a few valve types, above the 125 mm limit. Sodium valves are described here in a general manner, with no manufacturing details except when necessary for understanding valve behavior. Operating experience is pointed out wherever possible. Finally, some information is given about ongoing or proposed development plans. (U.S.)

Griswold Tempered Water Flow Regulator Valves Used as Anti-Siphon Valves

International Nuclear Information System (INIS)

MISKA, C.

2000-01-01

FCV-1*22 and 1*23 are Griswold constant flow regulators used as anti-siphon valves in the tempered water system, they fail closed but valve cartridge orifice allows minimum flow to prevent loss of water from the MCO/CASK annulus

Effects of aging and service wear on main steam isolation valves and valve operators

International Nuclear Information System (INIS)

Clark, R.L.

1996-03-01

In recent years main steam isolation valve (MSIV operating problems have resulted in significant operational transients (e.g., spurious reactor trips, steam generator dry out, excessive valve seat leakage), increased cost, and decreased plant availability. A key ingredient to an engineering-oriented reliability improvement effort is a thorough understanding of relevant historical experience. A detailed review of historical failure data available through the Institute of Nuclear Power Operation's Nuclear Plant Reliability Data System has been conducted for several types of MSIVs and valve operators for both boiling-water reactors and pressurized-water reactors. The focus of this review is on MSIV failures modes, actuator failure modes, consequences of failure on plant operations, method of failure detection, and major stressors affecting both valves and valve operators

Experimental substantiation of the design of a prosthetic heart valve for «valve-in-valve» implantation

Directory of Open Access Journals (Sweden)

K. Yu. Klyshnikov

2017-01-01

Full Text Available The aim of the study was to perform a series of in vitro tests of a prototype of the developing heart valve prosthesis to evaluate its functional characteristics. Materials and methods. In this work we have used the frames and full prototypes of the prosthesis, consisting of a stent-like stainless steel support frame with mounted biological leaflets and cover. The authors evaluated the calculated and experimental forces necessary for the displacement of the sutureless implanted prosthesis using the test machine under uniaxial tension. The risk of defects and damages to the supporting framework as a result of implantation was evaluated by scanning electron microscopy. The hydrodynamic characteristics of the prosthesis were investigated under physiological conditions and «valvein-valve» implantation. Evaluation of the ergonomics and applicability of the proposed construction on the cadaver heart model of cattle was carried out. Results. As a result of the forces assessment, it was found that the force required to shear the prosthesis was 3.12 ± 0.37 N, while the calculated value was 1.7 N, which is significantly lower than the obtained value. The comparison of the images obtained with small and large magnifications demonstrated the absence of critical surface defects. Additional analysis under the super-large magnifications also did not reveal problem areas. During the hydrodynamic study, it was shown that the average transplant gradient increased slightly from 2.8–3.4 to 3.2–4.5 mm Hg for the initial prosthesis and the «valve-in-valve» complex, respectively. The decrease of the effective orifice area was 6–9% relative to the initial one. Evaluation of the implantation technique demonstrated the consistency of the approach: the use of the developed holder in combination with the balloon implantation system made it possible to position the prosthesis throughout the procedure. Conclusion. The series of tests demonstrates the consistency

Valve-sparing aortic root replacement†

NARCIS (Netherlands)

Koolbergen, David R.; Manshanden, Johan S. J.; Bouma, Berto J.; Blom, Nico A.; Mulder, Barbara J. M.; de Mol, Bas A. J. M.; Hazekamp, Mark G.

2015-01-01

To evaluate our results of valve-sparing aortic root replacement and associated (multiple) valve repair. From September 2003 to September 2013, 97 patients had valve-sparing aortic root replacement procedures. Patient records and preoperative, postoperative and recent echocardiograms were reviewed.

Mitral valve-sparing procedures and prosthetic heart valve failure: A case report

Science.gov (United States)

Khan, Nasir A; Butany, Jagdish; Leong, Shaun W; Rao, Vivek; Cusimano, Robert J; Ross, Heather J

2009-01-01

Prosthetic heart valve dysfunction due to thrombus or pannus formation can be a life-threatening complication. The present report describes a 47-year-old woman who developed valvular cardiomyopathy after chorda-sparing mitral valve replacement, and subsequently underwent heart transplantation for progressive heart failure. The explanted mitral valve prosthesis showed significant thrombus and pannus leading to reduced leaflet mobility and valvular stenosis. The present report illustrates the role of the subvalvular apparatus and pannus in prosthesis dysfunction. PMID:19279993

Modeling of the energy savings of variable recruitment McKibben muscle bundles

Science.gov (United States)

Meller, Michael A.; Chipka, Jordan B.; Bryant, Matthew J.; Garcia, Ephrahim

2015-03-01

McKibben artificial muscles are often utilized in mobile robotic applications that require compliant and light weight actuation capable of producing large forces. In order to increase the endurance of these mobile robotic platforms, actuation efficiency must be addressed. Since pneumatic systems are rarely more than 30% efficient due to the compressibility of the working fluid, the McKibben muscles are hydraulically powered. Additionally, these McKibben artificial muscles utilize an inelastic bladder to reduce the energy losses associated with elastic energy storage in the usual rubber tube bladders. The largest energy losses in traditional valve-controlled hydraulic systems are found in the valving implementation to match the required loads. This is performed by throttling, which results in large pressure drops over the control valves and significant fluid power being wasted as heat. This paper discusses how these throttling losses are reduced by grouping multiple artificial muscles to form a muscle bundle where, like in skeletal muscle, more elements that make up the muscle bundle are recruited to match the load. This greatly lessens the pressure drops by effectively changing the actuator area, leading to much higher efficiencies over a broader operation envelope. Simulations of several different loading scenarios are discussed that reveal the benefits of such an actuation scheme.

Analysis of aortic root surgery with composite mechanical aortic valve conduit and valve-sparing reconstruction.

Science.gov (United States)

Dias, Ricardo Ribeiro; Mejia, Omar Asdrubal Vilca; Fiorelli, Alfredo Inácio; Pomerantzeff, Pablo Maria Alberto; Dias, Altamiro Ribeiro; Mady, Charles; Stolf, Noedir Antonio Groppo

2010-01-01

Comparative analysis of early and late results of aortic root reconstruction with aortic valve sparing operations and the composite mechanical valve conduit replacement. From November 2002 to September 2009, 164 consecutive patients with mean age 54 ± 15 years, 115 male, underwent the aortic root reconstruction (125 mechanical valve conduit replacements and 39 valve sparing operations). Sixteen percent of patients had Marfan syndrome and 4.3% had bicuspid aortic valve. One hundred and forty-four patients (88%) were followed for a mean period of 41.1 ± 20.8 months. The hospital mortality was 4.9%, 5.6% in operations with valved conduits and 2.6% in the valve sparing procedures (P valve sparing operations, respectively (95% CI = 70% - 95%, P = 0.001), (95% CI = 82% - 95% P = 0.03) and (95% CI = 81% - 95%, P = 0.03). Multivariate analysis showed that creatinine greater than 1.4 mg/dl, Cabrol operation and renal dialysis were predictors of mortality, respectively, with occurrence chance of 6 (95% CI = 1.8 - 19.5, P = 0.003), 12 (95% CI = 3 - 49.7, P = 0.0004) and 16 (95% CI = 3.6 - 71.3, P = 0.0002). The aortic root reconstruction has a low early and late mortality, high survival free of complications and low need for reoperation. During the late follow-up, valve sparing aortic root reconstructions presented fewer incidences of bleeding, thromboembolic events and endocarditis.

Simple Check Valves for Microfluidic Devices

Science.gov (United States)

Willis, Peter A.; Greer, Harold F.; Smith, J. Anthony

2010-01-01

A simple design concept for check valves has been adopted for microfluidic devices that consist mostly of (1) deformable fluorocarbon polymer membranes sandwiched between (2) borosilicate float glass wafers into which channels, valve seats, and holes have been etched. The first microfluidic devices in which these check valves are intended to be used are micro-capillary electrophoresis (microCE) devices undergoing development for use on Mars in detecting compounds indicative of life. In this application, it will be necessary to store some liquid samples in reservoirs in the devices for subsequent laboratory analysis, and check valves are needed to prevent cross-contamination of the samples. The simple check-valve design concept is also applicable to other microfluidic devices and to fluidic devices in general. These check valves are simplified microscopic versions of conventional rubber- flap check valves that are parts of numerous industrial and consumer products. These check valves are fabricated, not as separate components, but as integral parts of microfluidic devices. A check valve according to this concept consists of suitably shaped portions of a deformable membrane and the two glass wafers between which the membrane is sandwiched (see figure). The valve flap is formed by making an approximately semicircular cut in the membrane. The flap is centered over a hole in the lower glass wafer, through which hole the liquid in question is intended to flow upward into a wider hole, channel, or reservoir in the upper glass wafer. The radius of the cut exceeds the radius of the hole by an amount large enough to prevent settling of the flap into the hole. As in a conventional rubber-flap check valve, back pressure in the liquid pushes the flap against the valve seat (in this case, the valve seat is the adjacent surface of the lower glass wafer), thereby forming a seal that prevents backflow.

Aortic Regurgitation in Patients Undergoing Transcatheter Aortic Valve Replacement With the Self-Expanding CoreValve Versus the Balloon-Expandable SAPIEN XT Valve.

Science.gov (United States)

Kiramijyan, Sarkis; Magalhaes, Marco A; Koifman, Edward; Didier, Romain; Escarcega, Ricardo O; Baker, Nevin C; Negi, Smita I; Minha, Sa'ar; Torguson, Rebecca; Jiaxiang, Gai; Asch, Federico M; Wang, Zuyue; Okubagzi, Petros; Gaglia, Michael A; Ben-Dor, Itsik; Satler, Lowell F; Pichard, Augusto D; Waksman, Ron

2016-05-01

The incidence of aortic regurgitation (AR) after transcatheter aortic valve replacement (TAVR) in a self-expanding and a balloon-expandable system is controversial. This study aimed to examine the incidence and severity of post-TAVR AR with the CoreValve (CV) versus the Edwards XT Valve (XT). Baseline, procedural, and postprocedural inhospital outcomes were compared. The primary end point was the incidence of post-TAVR AR of any severity, assessed with a transthoracic echocardiogram, in the CV versus XT groups. A multivariate logistic regression analysis was completed to evaluate for correlates of the primary end point. The secondary end points included the change in severity of AR at 30-day and 1-year follow-up. A total of 223 consecutive patients (53% men, mean age 82 years) who had transfemoral TAVR with either a CV (n = 119) or XT (n = 104) were evaluated. The rates of post-TAVR AR in the groups were similar, and there was no evidence of more-than-moderate AR in either group. There were significant differences in the rates of intraprocedural balloon postdilation with the CV (17.1%) versus XT valve (5.8%; p = 0.009) and in the rates of intraprocedural implantation of a second valve-in-valve prosthesis with the CV (9.9%) versus XT valve (2.2%; p = 0.036). There were no significant differences in inhospital safety outcomes between the 2 groups. In conclusion, the incidence of post-TAVR AR is similar between the CV and the XT valve when performed by experienced operators using optimal intraprocedural strategies, as deemed appropriate, to mitigate the severity of AR. Copyright © 2016 Elsevier Inc. All rights reserved.

Pannus Formation Leads to Valve Malfunction in the Tricuspid Position 19 Years after Triple Valve Replacement.

Science.gov (United States)

Alskaf, Ebraham; McConkey, Hannah; Laskar, Nabila; Kardos, Attila

2016-06-20

The Medtronic ATS Open Pivot mechanical valve has been successfully used in heart valve surgery for more than two decades. We present the case of a patient who, 19 years following a tricuspid valve replacement with an ATS prosthesis as part of a triple valve operation following infective endocarditis, developed severe tricuspid regurgitation due to pannus formation.

Recurrent pannus formation causing prosthetic aortic valve dysfunction: is excision without valve re-replacement applicable?

Science.gov (United States)

Darwazah, Ahmad K

2012-06-29

Prosthetic valve dysfunction at aortic position is commonly caused by pannus formation. The exact etiology is not known. It arises from ventricular aspect of the prosthesis encroaching its leaflets causing stenosis or it may remain localized causing left ventricular outflow tract obstruction without affecting valve function.The difference in location entails different approaches in management. Such a pathology requires surgical excision of the pannus with or without valve re-replacement.A recurrent pannus was observed in a female patient who needed repeated surgical intervention to excise a localized pannus without re-replacement of a well functioning prosthetic valve.Management of our case presents several questions, whether recurrence of pannus is caused by sparing the prosthetic valve, is it simply an exaggeration of an inflammatory healing process in certain individuals or is it ideal to re-replace the valve despite a well preserved function.

Valve-sparing aortic root replacement†.

Science.gov (United States)

Koolbergen, David R; Manshanden, Johan S J; Bouma, Berto J; Blom, Nico A; Mulder, Barbara J M; de Mol, Bas A J M; Hazekamp, Mark G

2015-02-01

To evaluate our results of valve-sparing aortic root replacement and associated (multiple) valve repair. From September 2003 to September 2013, 97 patients had valve-sparing aortic root replacement procedures. Patient records and preoperative, postoperative and recent echocardiograms were reviewed. Median age was 40.3 (range: 13.4-68.6) years and 67 (69.1%) were male. Seven (7.2%) patients were younger than 18 years, the youngest being 13.4 years. Fifty-four (55.7%) had Marfan syndrome, 2 (2.1%) other fibrous tissue diseases, 15 (15.5%) bicuspid aortic valve and 3 (3.1%) had earlier Fallot repair. The reimplantation technique was used in all, with a straight vascular prosthesis in 11 (26-34 mm) and the Valsalva prosthesis in 86 (26-32 mm). Concomitant aortic valve repair was performed in 43 (44.3%), mitral valve repair in 10 (10.3%), tricuspid valve repair in 5 (5.2%) and aortic arch replacement in 3 (3.1%). Mean follow-up was 4.2 ± 2.4 years. Follow-up was complete in all. One 14-year old patient died 1.3 years post-surgery presumably of ventricular arrhythmia. One patient underwent reoperation for aneurysm of the proximal right coronary artery after 4.9 years and 4 patients required aortic valve replacement, 3 of which because of endocarditis after 0.1, 0.8 and 1.3 years and 1 because of cusp prolapse after 3.8 years. No thrombo-embolic complications occurred. Mortality, root reoperation and aortic regurgitation were absent in 88.0 ± 0.5% at 5-year follow-up. Results of valve-sparing root replacement are good, even in association with a high incidence of concomitant valve repair. Valve-sparing aortic root replacement can be performed at a very young age as long as an adult size prosthesis can be implanted. © The Author 2014. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.

Axial computed tomography evaluation of the internal nasal valve correlates with clinical valve narrowing and patient complaint.

Science.gov (United States)

Moche, Jason A; Cohen, Justin C; Pearlman, Steven J

2013-07-01

The objective of this work was to explore the utility of axial computed tomography (CT) imaging to objectively define a narrow internal nasal valve, and compare those findings with clinical examination and patient complaint. Retrospective review from a single facial plastic surgery center. We reviewed 40 consecutive patients evaluated for either sinusitis or nasal airway obstruction for which a CT scan was obtained at a single radiology institution. Thirty-six complete office records were examined for the presence of clinical internal valve narrowing and complaints of nasal obstruction. In total, 72 internal nasal valves were analyzed using axial plane CT and measurements were compared to clinical findings and presence of airway obstruction. Measured valve areas for clinically normal internal nasal valves averaged 0.47 cm(2) vs 0.28 cm(2) for clinically narrow valves, a decrease of 40.4%. In unobstructed nasal airways the valve area averaged 0.51 cm(2) vs 0.38 cm(2) in obstructed airways, a difference of 25.5%. A radiographically measured valve area of <0.30 cm(2) suggests clinical narrowing with a sensitivity of 71.4%, specificity of 88.9%, positive predictive value of 62.5%, and negative predictive value of 92.3%. Using standard axial CT imaging we describe an objective method of radiographically evaluating the nasal valve, demonstrating strong correlation with physical examination and patient complaint. Additionally, radiographic valve areas can be used to screen for clinically narrow nasal valves with good sensitivity and specificity, providing a novel straightforward method for nasal valve assessment. © 2012 ARS-AAOA, LLC.

Small sodium valve design and operating experience

International Nuclear Information System (INIS)

McGough, C.B.

1974-01-01

The United States Liquid Metal Fast Breeder Reactor program (LMFBR) includes an extensive program devoted to the development of small sodium valves. This program is now focused on the development and production of valves for the Fast Flux Test Facility (FFTF) now under construction near Richland, Washington. Other AEC support facilities, such as various test loops located at the Liquid Metal Engineering Center (LMEC), Los Angeles, California, and at the Hanford Engineering Development Laboratory (HEDL), Richland, Washington, also have significant requirements for small sodium valves, and valves similar in design to the FFTF valves are being supplied to these AEC laboratories for use in their critical test installations. A principal motivation for these valve programs, beyond the immediate need to provide high-reliability valves for FFTF and the support facilities, is the necessity to develop small valve technology for the Clinch River Breeder Reactor Plant (CRBRP). FFTF small sodium valve design and development experience will be directly applied to the CRBRP program. Various test programs have been, and are being, conducted to verify the performance and integrity of the FFTF valves, and to uncover any potential problems so that they can be corrected before the valves are placed in service in FFTF. The principal small sodium valve designs being utilized in current U.S. programs, the test and operational experience obtained to date on them, problems uncovered, and future development and testing efforts being planned are reviewed. The standards and requirements to which the valves are being designed and fabricated, the valve designs in current use, valve operators, test and operating experience, and future valve development plans are summarized. (U.S.)

Developments in mechanical heart valve prosthesis

Indian Academy of Sciences (India)

Artificial heart valves are engineered devices used for replacing diseased or damaged natural valves of the heart. Most commonly used for replacement are mechanical heart valves and biological valves. This paper briefly outlines the evolution, designs employed, materials being used,. and important factors that affect the ...

Ball check valve

International Nuclear Information System (INIS)

Bevilacqua, F.

1978-01-01

A pressurized nuclear reactor having an instrument assembly sheathed in a metallic tube which is extended vertically upward into the reactor core by traversing a metallic guide tube which is welded to the wall of the vessel is described. Sensors in each instrument assembly are connected to instruments outside the vessel to manifest the conditions within the core. Each instrument assembly probe is moved into position within a metallic guide channel. The guide channel penetrates the wall of the vessel and forms part of the barrier to the environment within the pressure vessel. Each channel includes a ball check valve which is opened by the instrument assembly probe when the probe passes through the valve. A ball valve element is moved from its seat by the probe to a position lateral of the bore of the channel and is guided to its seat along a sloped path within the valve body when the probe is removed. 5 claims, 3 figures

LOFT pressurizer safety: relief valve reliability

Energy Technology Data Exchange (ETDEWEB)

Brown, E.S.

1978-01-18

The LOFT pressurizer self-actuating safety-relief valves are constructed to the present state-of-the-art and should have reliability equivalent to the valves in use on PWR plants in the U.S. There have been no NRC incident reports on valve failures to lift that would challenge the Technical Specification Safety Limit. Fourteen valves have been reported as lifting a few percentage points outside the +-1% Tech. Spec. surveillance tolerance (9 valves tested over and 5 valves tested under specification). There have been no incident reports on failures to reseat. The LOFT surveillance program for assuring reliability is equivalent to nuclear industry practice.

LOFT pressurizer safety: relief valve reliability

International Nuclear Information System (INIS)

Brown, E.S.

1978-01-01

The LOFT pressurizer self-actuating safety-relief valves are constructed to the present state-of-the-art and should have reliability equivalent to the valves in use on PWR plants in the U.S. There have been no NRC incident reports on valve failures to lift that would challenge the Technical Specification Safety Limit. Fourteen valves have been reported as lifting a few percentage points outside the +-1% Tech. Spec. surveillance tolerance (9 valves tested over and 5 valves tested under specification). There have been no incident reports on failures to reseat. The LOFT surveillance program for assuring reliability is equivalent to nuclear industry practice

Cavitation guide for control valves

Energy Technology Data Exchange (ETDEWEB)

Tullis, J.P. [Tullis Engineering Consultants, Logan, UT (United States)

1993-04-01

This guide teaches the basic fundamentals of cavitation to provide the reader with an understanding of what causes cavitation, when it occurs, and the potential problems cavitation can cause to a valve and piping system. The document provides guidelines for understanding how to reduce the cavitation and/or select control valves for a cavitating system. The guide provides a method for predicting the cavitation intensity of control valves, and how the effect of cavitation on a system will vary with valve type, valve function, valve size, operating pressure, duration of operation and details of the piping installation. The guide defines six cavitation limits identifying cavitation intensities ranging from inception to the maximum intensity possible. The intensity of the cavitation at each limit Is described, including a brief discussion of how each level of cavitation influences the valve and system. Examples are included to demonstrate how to apply the method, including making both size and pressure scale effects corrections. Methods of controlling cavitation are discussed providing information on various techniques which can be used to design a new system or modify an existing one so it can operate at a desired level of cavitation.

Cavitation guide for control valves

International Nuclear Information System (INIS)

Tullis, J.P.

1993-04-01

This guide teaches the basic fundamentals of cavitation to provide the reader with an understanding of what causes cavitation, when it occurs, and the potential problems cavitation can cause to a valve and piping system. The document provides guidelines for understanding how to reduce the cavitation and/or select control valves for a cavitating system. The guide provides a method for predicting the cavitation intensity of control valves, and how the effect of cavitation on a system will vary with valve type, valve function, valve size, operating pressure, duration of operation and details of the piping installation. The guide defines six cavitation limits identifying cavitation intensities ranging from inception to the maximum intensity possible. The intensity of the cavitation at each limit Is described, including a brief discussion of how each level of cavitation influences the valve and system. Examples are included to demonstrate how to apply the method, including making both size and pressure scale effects corrections. Methods of controlling cavitation are discussed providing information on various techniques which can be used to design a new system or modify an existing one so it can operate at a desired level of cavitation

Outcome of pregnancy in women after pulmonary autograft valve replacement for congenital aortic valve disease

NARCIS (Netherlands)

Yap, Sing-Chien; Drenthen, Willem; Pieper, Petronella G.; Moons, Philip; Mulder, Barbara J. M.; Klieverik, Loes M.; Vliegen, Hubert W.; van Dijk, Arie P. J.; Meijboom, Folkert J.; Roos-Hesselink, Jolien W.

Background and aim of the study: The pulmonary autograft has been recommended as the valve of choice for aortic valve replacement (AVR) in young women contemplating pregnancy. However, current information on maternal and perinatal outcome of pregnancy in women with pulmonary autograft valve

Outcome of pregnancy in women after pulmonary autograft valve replacement for congenital aortic valve disease

NARCIS (Netherlands)

Yap, Sing-Chien; Drenthen, Willem; Pieper, Petronella G.; Moons, Philip; Mulder, Barbara J. M.; Klieverik, Loes M.; Vliegen, Hubert W.; van Dijk, Arie P. J.; Meijboom, Folkert J.; Roos-Hesselink, Jolien W.

2007-01-01

Background and aim of the study: The pulmonary autograft has been recommended as the valve of choice for aortic valve replacement (AVR) in young women contemplating pregnancy. However, current information on maternal and perinatal outcome of pregnancy in women with pulmonary autograft valve

Outcome of pregnancy in women after pulmonary autograft valve replacement for congenital aortic valve disease.

NARCIS (Netherlands)

Yap, S.C.; Drenthen, W.; Pieper, P.G.; Moons, P.; Mulder, B.J.M.; Klieverik, L.M.; Vliegen, H.W.; Dijk, A.P.J. van; Meijboom, F.J.; Roos-Hesselink, J.W.

2007-01-01

BACKGROUND AND AIM OF THE STUDY: The pulmonary autograft has been recommended as the valve of choice for aortic valve replacement (AVR) in young women contemplating pregnancy. However, current information on maternal and perinatal outcome of pregnancy in women with pulmonary autograft valve

Recurrent pannus formation causing prosthetic aortic valve dysfunction: Is excision without valve re-replacement applicable?

Directory of Open Access Journals (Sweden)

Darwazah Ahmad K

2012-06-01

Full Text Available Abstract Prosthetic valve dysfunction at aortic position is commonly caused by pannus formation. The exact etiology is not known. It arises from ventricular aspect of the prosthesis encroaching its leaflets causing stenosis or it may remain localized causing left ventricular outflow tract obstruction without affecting valve function. The difference in location entails different approaches in management. Such a pathology requires surgical excision of the pannus with or without valve re-replacement. A recurrent pannus was observed in a female patient who needed repeated surgical intervention to excise a localized pannus without re-replacement of a well functioning prosthetic valve. Management of our case presents several questions, whether recurrence of pannus is caused by sparing the prosthetic valve, is it simply an exaggeration of an inflammatory healing process in certain individuals or is it ideal to re-replace the valve despite a well preserved function.

Butterfly valve of all rubber lining type

International Nuclear Information System (INIS)

Shimada, Shosaku; Nakatsuma, Sumiya; Sasaki, Iwao; Aoki, Naoshi.

1982-01-01

The valves used for the circulating water pipes for condensers in nuclear and thermal power stations have become large with the increase of power output, and their specifications have become strict. The materials for the valves change from cast iron to steel plate construction. To cope with sea water corrosion, rubber lining has been applied to the internal surfaces of valve boxes, and the build-up welding of stainless steel has been made on the edges of valves. However, recently it is desired to develop butterfly valves, of which the whole valve disks are lined with hard rubber. For the purpose of confirming the performance of large bore valves, a 2600 mm bore butterfly valve of all rubber lining type was used, and the opening and closing test of 1100 times was carried out by applying thermal cycle and pressure difference and using artifical sea water. Also the bending test of hard rubber lining was performed with test pieces. Thus, it was confirmed that the butterfly valves of all rubber lining type have the performance exceeding that of the valves with build-up welding. The course of development of the valves of all rubber lining type, the construction and the items of confirmation by tests of these valves, and the tests of the valve and the hard rubber lining described above are reported. (Kako, I.)

A STUDY OF INDICATIONS, COMPLICATIONS OF PROSTHETIC VALVES AND PROGNOSIS AFTER TREATMENT OF STUCK VALVE

Directory of Open Access Journals (Sweden)

Y. V. Subba Reddy

2017-03-01

Full Text Available BACKGROUND Implantation of prosthetic cardiac valves to treat haemodynamically significant valvular diseases has become common; however, it is associated with complications. Thus, this study was intended to evaluate the indications for implantation of prosthetic valve and complications after its implantation and prognosis after treatment of one of its complication, i.e. stuck valve. MATERIALS AND METHODS This was a single-centered study wherein 50 patients who came to the emergency department with stuck valve were assessed. The 2D echocardiography was performed in all patients. Thrombolysis was done and the gradients were reassessed. Further response to treatment and development of complications before and after treatment were observed. RESULTS Of total patients, 60% were females. Mean age group was 30-40 yrs. Most of them were asymptomatic for 6 years and there was lack of compliance in 90% of patients. Most common indication for valve replacement was mitral stenosis (60% followed by mitral regurgitation (20%, aortic regurgitation and aortic stenosis (10% and combined mitral and tricuspid regurgitation (10%. Commonest valve was St. Jude (90%. Pannus was observed in 10% patients and thrombus was observed in 50% patients. Most patients had gradients 45/20 mmHg across mitral valve. In about 90% patients, gradients decreased after thrombolysis (12/5 mmHg. The complications after thrombolysis were hemiparesis (4%, death before thrombolysis (6% and death after thrombolysis (4%. CONCLUSION Considering these results, it can be concluded that prosthetic valves are seldom associated with some complications. Further, thrombolysis can be effective in patients with prosthetic valve thrombosis.

Supra-annular Valve-in-Valve implantation reduces blood stasis on the transcatheter aortic valve leaflets.

Science.gov (United States)

Vahidkhah, Koohyar; Azadani, Ali N

2017-06-14

Leaflet thrombosis following transcatheter aortic valve replacement (TAVR) and Valve-in-Valve (ViV) procedures has been increasingly recognized. This study aimed to investigate the effect of positioning of the transcatheter aortic valve (TAV) in ViV setting on the flow dynamics aspect of post-ViV thrombosis by quantifying the blood stasis in the intra-annular and supra-annular settings. To that end, two idealized computational models, representing ViV intra-annular and supra-annular positioning of a TAV were developed in a patient-specific geometry. Three-dimensional flow fields were then obtained via fluid-solid interaction modeling to study the difference in blood residence time (BRT) on the TAV leaflets in the two settings. At the end of diastole, a strip of high BRT (⩾1.2s) region was observed on the TAV leaflets in the ViV intra-annular positioning at the fixed boundary where the leaflets are attached to the frame. Such a high BRT region was absent on the TAV leaflets in the supra-annular positioning. The maximum value of BRT on the surface of non-, right, and left coronary leaflets of the TAV in the supra-annular positioning were 53%, 11%, and 27% smaller compared to the intra-annular positioning, respectively. It was concluded that the geometric confinement of TAV by the leaflets of the failed bioprosthetic valve in ViV intra-annular positioning increases the BRT on the leaflets and may act as a permissive factor in valvular thrombosis. The absence of such a geometric confinement in the ViV supra-annular positioning leads to smaller BRT and subsequently less likelihood of leaflet thrombosis. Copyright © 2017 Elsevier Ltd. All rights reserved.

Theoretical and experimental results of a mesoscale electric power generation system from pressurized gas flow

International Nuclear Information System (INIS)

Krähenbühl, D; Kolar, J W; Zwyssig, C; Weser, H

2009-01-01

In many process applications where throttling is used to reduce pressure, the potential to obtain net work output is sacrificed to the throttling process. Examples are throttling valves of gas pipelines and conventional throttles in automotive applications or turbo expanders as used in cryogenic plants. With a new pressure reduction system that produces electricity while expanding the gas, the lost potential to obtain work output can be recovered. To achieve a high power density, this energy generation system requires an increased operating speed of the electrical machine and the turbomachinery. This paper presents a miniature compressed-air-to-electric-power system, based on a radial turbine with a rated rotational speed of 490 000 rpm and a rated electric power output of 150 W. A comprehensive description including turbine, diffuser and permanent magnet (PM) generator is given. Finally, measurements of the compressed-air-to-electric-power system with a maximum rotational speed of over 600 000 rpm, a maximum electric output power of 170 W, a maximum torque of 5.2 mN m and a turbine efficiency of 52% are presented

Resurgery for recurrent heart valve diseases

Directory of Open Access Journals (Sweden)

Chong-lei REN

2017-02-01

Full Text Available Objective　To summarize the experience with resurgery for recurrent valvular heart diseases. Methods　From June 2004 to June 2015, 28 patients (15 males and 13 females with ages ranging from 44 to 67 years (55.6±6.5 years with recurrent heart valve disease underwent resurgery. The reasons for resurgery included perivalvular leakage (7 cases, bioprosthetic valve decline (6 cases in mitral valve and 3 in tricuspid valve, mechanical prostheses dysfunction (2cases, infective endocarditis after valve replacement (2 cases, restenosis of repaired native valve (1 case, and severe tricuspid insufficiency after left-side valve surgery (7 cases. Resurgery included mitral valve replacement in 18 patients and tricuspid valve replacement in 10. All the patients underwent third or fourth or even fifth cardiac surgery for valve replacement. Results　There were 2 hospital deaths with a mortality of 7.1% (2/28. The main causes of early-stage deaths were low cardiac output syndrome. The main postoperative complications were respiratory failure in 3, low cardiac output syndrome in 2, reexploration for bleeding in 2 and serious infectious shock in 1. All the patients were found with the great improvement in heart function and the re-implanted prostheses worked well during follow-up. Conclusions　Although resurgery for recurrent heart valve disease poses a continuing challenge to cardiac surgeon, it could be performed with the satisfactory results. The keys to a successful cardiac resurgery include appropriate operational timing, refined surgical technique and reasonable perioperative managements. DOI: 10.11855/j.issn.0577-7402.2017.01.11

Design of the Modular Pneumatic Valve Terminal

Directory of Open Access Journals (Sweden)

Jakub E. TAKOSOGLU

2015-11-01

Full Text Available The paper presents design of the modular pneumatic valve terminal, which was made on the basis of the patent application No A1 402905 „A valve for controlling fluid power drives, specially for pneumatic actuators, and the control system for fluid power drives valves”. The authors describe a method of operation of the system with double-acting valve and 5/2 (five ways and two position valve. Functions of the valve, and an example of application of the valve terminal in the production process were presented. 3D solid models of all the components of the valve were made. The paper presents a complete 3D model of the valve in various configurations. Using CAD-embedded SOLIDWORKS Flow Simulation computational fluid dynamics CFD analysis was also carried out of compressed air flow in the ways of the valve elements

Valve-stem-packing improvement study. Final report

International Nuclear Information System (INIS)

Adey, C.W.; Klein, J.J.

1982-08-01

By employing questionnaires and face-to-face interviews with valve and valve packing manufacturers, as well as nuclear plant personnel, an understanding of valve stem packing leakage problems from each of the three viewpoints was developed. This information, in-house experience, and available technical literature were used to develop specific recommendations for valve manufacturers, valve packing manufacturers, and nuclear plant valve users. It was generally recommended that each these groups make better use of graphite packing. The questionnaires and interviews indicated that increased usage of graphite packing over the last few years has reduced the incidence of valve packing problems. To confirm this, a survey of Licensee Event Reports (LERs) from 1972 to 1980 was undertaken using the keywords Valve and Packing. A statistical analysis of the LER data confirms that the adoption of graphite packing has significantly reduced valve stem leakage

Double-reed exhaust valve engine

Science.gov (United States)

Bennett, Charles L.

2015-06-30

An engine based on a reciprocating piston engine that extracts work from pressurized working fluid. The engine includes a double reed outlet valve for controlling the flow of low-pressure working fluid out of the engine. The double reed provides a stronger force resisting closure of the outlet valve than the force tending to open the outlet valve. The double reed valve enables engine operation at relatively higher torque and lower efficiency at low speed, with lower torque, but higher efficiency at high speed.

Survey of industrial coal conversion equipment capabilities: valves

Energy Technology Data Exchange (ETDEWEB)

Bush, W. A.; Slade, E. C.

1978-06-01

A survey of the industrial capabilities of the valve and valve-actuator industry to supply large, high-pressure stop valves for the future coal conversion industry is presented in this report. Also discussed are development and testing capabilities of valve and valve-actuator manufacturers and anticipated lead times required to manufacture advanced design valves for the most stringent service applications. Results indicate that the valve and valve-actuator industry is capable of manufacturing in quantity equipment of the size and for the pressure and temperature ranges which would be required in the coal conversion industry. Valve manufacturers do not, however, have sufficient product application experience to predict the continuing functional ability of valves used for lock-hopper feeders, slurry feeders, and slag-char letdown service. Developmental and testing efforts to modify existing valve designs or to develop new valve concepts for these applications were estimated to range from 1 to 6 years. A testing facility to simulate actuation of critical valves under service conditions would be beneficial.

Gate valve and motor-operator research findings

International Nuclear Information System (INIS)

Steele, R. Jr.; DeWall, K.G.; Watkins, J.C.; Russell, M.J.; Bramwell, D.

1995-09-01

This report provides an update on the valve research being sponsored by the US Nuclear Regulatory Commission (NRC) and conducted at the Idaho National Engineering Laboratory (INEL). The research addresses the need to provide assurance that motor-operated valves can perform their intended safety function, usually to open or close against specified (design basis) flow and pressure loads. This report describes several important developments: Two methods for estimating or bounding the design basis stem factor (in rising-stem valves), using data from tests less severe than design basis tests; a new correlation for evaluating the opening responses of gate valves and for predicting opening requirements; an extrapolation method that uses the results of a best effort flow test to estimate the design basis closing requirements of a gate valve that exhibits atypical responses (peak force occurs before flow isolation); and the extension of the original INEL closing correlation to include low- flow and low-pressure loads. The report also includes a general approach, presented in step-by-step format, for determining operating margins for rising-stem valves (gate valves and globe valves) as well as quarter-turn valves (ball valves and butterfly valves)

Valve leakage inspection testing and maintenance process

International Nuclear Information System (INIS)

Aikin, J.A.; Reinwald, J.W.; Kittmer, C.A.

1991-01-01

In valve maintenance, packing rings that prevent leakage along the valve stem must periodically be replaced, either during routine maintenance or to correct a leak or valve malfunction. Tools and procedures currently in use for valve packing removal and inspection are generally of limited value due to various access and application problems. A process has been developed by AECL Research that addresses these problems. The process, using incompressible fluid pressure, quickly and efficiently confirms the integrity of the valve backseat, extracts hard-to-remove valve packing sets, and verifies the leak tightness of the repacked valve

Strut fracture of Björk-Shiley convexo-concave valve in Japan--risk of small valve size--.

Science.gov (United States)

Watarida, S; Shiraishi, S; Nishi, T; Imura, M; Yamamoto, Y; Hirokawa, R; Fujita, M

2001-08-01

The Björk-Shiley convexo-concave (BSCC) prosthetic valve was introduced in 1979. Between 1979 and 1986, approximately 86,000 BSCC valves were implanted. By December 31, 1994, 564 complete strut fractures had been reported to the manufacture. We experienced a case of an outlet strut fracture and investigated the risk of BSCC prosthetic valve fractures in Japan. To investigate the risk factor of a strut fracture in Japan, we investigated published cases of strut fractures. Between 1979 and 1986, 2021 BSCC valves were implanted in Japan. By January 31, 2000, 11 complete strut fractures of 60-degree BSCC valves including our case had occurred. The patients were eight males and three females. The average age at valve replacement was 42.4+/-8.1 years, and nine of eleven (81.8%) were patients valve fractured was 47.7+/-6.4 years, and eight of eleven (72.7%) were patients valve were 27 mm (n=5) (45.5%), 29 mm (n=3) (27.2%), and 31 mm (n=3) (27.2%). Four patients died and seven patients survived. Although only 11 BSCC valve struts fractured and statistical analysis could not be performed, our findings suggest that the high risk group for a strut fracture in Japan is young male patients with a mitral valve, >= 27 mm in size with BSCC models manufactured before March 1982. When following-up patients with BSCC models manufactured before March 1982, the possibility of a strut fracture in all BSCC valve sizes should be kept in mind.

Transcatheter pulmonary valve replacement by hybrid approach using a novel polymeric prosthetic heart valve: proof of concept in sheep.

Directory of Open Access Journals (Sweden)

Ben Zhang

Full Text Available Since 2000, transcatheter pulmonary valve replacement has steadily advanced. However, the available prosthetic valves are restricted to bioprosthesis which have defects like poor durability. Polymeric heart valve is thought as a promising alternative to bioprosthesis. In this study, we introduced a novel polymeric transcatheter pulmonary valve and evaluated its feasibility and safety in sheep by a hybrid approach.We designed a novel polymeric trileaflet transcatheter pulmonary valve with a balloon-expandable stent, and the valve leaflets were made of 0.1-mm expanded polytetrafluoroethylene (ePTFE coated with phosphorylcholine. We chose glutaraldehyde-treated bovine pericardium valves as control. Pulmonary valve stents were implanted in situ by a hybrid transapical approach in 10 healthy sheep (8 for polymeric valve and 2 for bovine pericardium valve, weighing an average of 22.5±2.0 kg. Angiography and cardiac catheter examination were performed after implantation to assess immediate valvular functionality. After 4-week follow-up, angiography, echocardiography, computed tomography, and cardiac catheter examination were used to assess early valvular function. One randomly selected sheep with polymeric valve was euthanized and the explanted valved stent was analyzed macroscopically and microscopically.Implantation was successful in 9 sheep. Angiography at implantation showed all 9 prosthetic valves demonstrated orthotopic position and normal functionality. All 9 sheep survived at 4-week follow-up. Four-week follow-up revealed no evidence of valve stent dislocation or deformation and normal valvular and cardiac functionality. The cardiac catheter examination showed the peak-peak transvalvular pressure gradient of the polymeric valves was 11.9±5.0 mmHg, while that of two bovine pericardium valves were 11 and 17 mmHg. Gross morphology demonstrated good opening and closure characteristics. No thrombus or calcification was seen macroscopically

Valve-sparing and valve-replacing techniques for aortic root replacement in patients with Marfan syndrome: Analysis of early outcome.

Science.gov (United States)

Volguina, Irina V; Miller, D Craig; LeMaire, Scott A; Palmero, Laura C; Wang, Xing Li; Connolly, Heidi M; Sundt, Thoralf M; Bavaria, Joseph E; Dietz, Harry C; Milewicz, Dianna M; Coselli, Joseph S

2009-05-01

A prospective, international registry study was initiated to provide contemporary comparative data on short-term clinical outcomes after aortic valve-sparing and aortic valve-replacing root operations in patients with Marfan syndrome. The purpose of this initial report is to describe the study design and to compare early outcomes in the first 151 enrolled patients. We assessed 30-day outcomes in 151 patients who met strict Ghent diagnostic criteria for Marfan syndrome and underwent aortic root replacement with either valve-replacing (n = 46) or valve-sparing techniques (n = 105) at one of 18 participating centers. In the valve replacement group, a mechanical composite valve graft was used in 39 (85%) patients and a bioprosthetic valve in 7 (15%). In the valve-sparing group, David V procedures were performed in 57 (54%) patients, David I in 38 (36%), David IV in 8 (8%), Florida sleeve in 1 (1%), and Yacoub remodeling in 1 (1%). No in-hospital or 30-day deaths occurred. Despite longer crossclamp and cardiopulmonary bypass times in the valve-sparing group, there were no significant between-group differences in postoperative complications. Thirty-day valve-related complications occurred in 2 (4%) patients undergoing valve replacement and in 3 (3%) undergoing valve-sparing procedures (P = .6). The analysis of early outcomes revealed that valve-sparing techniques were the most common approach to root replacement in patients with Marfan syndrome in these centers. The complexity of valve-sparing root replacement did not translate into any demonstrable adverse early outcomes. Subsequent analysis will compare the 3-year durability of these two surgical approaches.

Guidelines for valves in tritium service

International Nuclear Information System (INIS)

Weaver, W.W.

1994-01-01

Some undesirable practices and misapplications that caused valve-related failures are examined, and future courses of action are recommended to avoid repetition of these events. Desirable valve characteristics and practices that should be considered when selecting valves for use in tritium service are also discussed. Supporting logic for the desirability of these features is presented by discussing the mechanisms of valve degradation followed by examples of related events. Desirable valve and system features and operational actions are grouped into two categories: strongly recommended and recommended. 13 refs., 1 fig

An analytical investigation on the valve and centrifugal pump speed control with a constant differential pressure across the valve

International Nuclear Information System (INIS)

Jung, B. R.; Joo, K. I.; Lee, B. J.; Baek, S. J.; Noh, T. S.

2003-01-01

A valve opening and centrifugal pump speed control was investigated analytically in a simple pumping system where the differential pressure across the control valve is maintained constant over the required flow range. The valve control program was derived analytically only as a function of the required flow rate to maintain the constant differential pressure across the valve. The centrifugal pump speed control program was also derived analytically for the required flow rate for the constant differential pressure across the control valve. These derivations theoretically show that the independent control is possible between the valve and pump speed in a system with a constant valve pressure drop. In addition, it was shown that a linear pump speed control is impossible in maintaining the constant valve pressure drop

Application of Hydrodynamic Cavitation for Food and Bioprocessing

Science.gov (United States)

Gogate, Parag R.

Hydrodynamic cavitation can be simply generated by the alterations in the flow field in high speed/high pressure devices and also by passage of the liquid through a constriction such as orifice plate, venturi, or throttling valve. Hydrodynamic cavitation results in the formation of local hot spots, release of highly reactive free radicals, and enhanced mass transfer rates due to turbulence generated as a result of liquid circulation currents. These conditions can be suitably applied for intensification of different bioprocessing applications in an energy-efficient manner as compared to conventionally used ultrasound-based reactors. The current chapter aims at highlighting different aspects related to hydrodynamic cavitation, including the theoretical aspects for optimization of operating parameters, reactor designs, and overview of applications relevant to food and bioprocessing. Some case studies highlighting the comparison of hydrodynamic cavitation and acoustic cavitation reactors will also be discussed.

Butterfly valve torque prediction methodology

International Nuclear Information System (INIS)

Eldiwany, B.H.; Sharma, V.; Kalsi, M.S.; Wolfe, K.

1994-01-01

As part of the Motor-Operated Valve (MOV) Performance Prediction Program, the Electric Power Research Institute has sponsored the development of methodologies for predicting thrust and torque requirements of gate, globe, and butterfly MOVs. This paper presents the methodology that will be used by utilities to calculate the dynamic torque requirements for butterfly valves. The total dynamic torque at any disc position is the sum of the hydrodynamic torque, bearing torque (which is induced by the hydrodynamic force), as well as other small torque components (such as packing torque). The hydrodynamic torque on the valve disc, caused by the fluid flow through the valve, depends on the disc angle, flow velocity, upstream flow disturbances, disc shape, and the disc aspect ratio. The butterfly valve model provides sets of nondimensional flow and torque coefficients that can be used to predict flow rate and hydrodynamic torque throughout the disc stroke and to calculate the required actuation torque and the maximum transmitted torque throughout the opening and closing stroke. The scope of the model includes symmetric and nonsymmetric discs of different shapes and aspects ratios in compressible and incompressible fluid applications under both choked and nonchoked flow conditions. The model features were validated against test data from a comprehensive flowloop and in situ test program. These tests were designed to systematically address the effect of the following parameters on the required torque: valve size, disc shapes and disc aspect ratios, upstream elbow orientation and its proximity, and flow conditions. The applicability of the nondimensional coefficients to valves of different sizes was validated by performing tests on 42-in. valve and a precisely scaled 6-in. model. The butterfly valve model torque predictions were found to bound test data from the flow-loop and in situ testing, as shown in the examples provided in this paper

Aortic valve surgery - open

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... gov/ency/article/007408.htm Aortic valve surgery - open To use the sharing features on this page, ... separates the heart and aorta. The aortic valve opens so blood can flow out. It then closes ...

Problem: Mitral Valve Regurgitation

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... each time the left ventricle contracts. Watch an animation of mitral valve regurgitation A leaking mitral valve ... Not Alone Popular Articles 1 Understanding Blood Pressure Readings 2 Sodium and Salt 3 Heart Attack Symptoms ...

Problem: Heart Valve Regurgitation

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... should be completely closed For example: Watch an animation of mitral valve regurgitation A leaking mitral valve ... Not Alone Popular Articles 1 Understanding Blood Pressure Readings 2 Sodium and Salt 3 Heart Attack Symptoms ...

Experimental investigation of the fluid dynamic efficiency of a high performance multi-valve internal combustion engine during the intake phase: Influence of valve-valve interference phenomena

Directory of Open Access Journals (Sweden)

Algieri Angelo

2013-01-01

Full Text Available The purpose of the present work is the analysis of the fluid dynamic behavior of a high performance internal combustion engine during the intake phase. In particular, a four-valve spark-ignition engine has been characterized at the steady flow rig. Dimensionless discharge coefficients have been used to define the global fluid dynamic efficiency of the intake system, while the Laser Doppler Anemometry (LDA technique has been employed to evaluate the mean flow in the valve curtain area and to characterise the interference phenomena between the two intake valves. The investigation has shown the significant influence of the valve lift on the volumetric efficiency of the intake apparatus. Moreover, the experimental analysis has highlighted that the valve-valve interference phenomena have a relevant impact on the head breathability, on the flow development within the combustion chamber and on the velocity standard deviations.

Are anticoagulant independent mechanical valves within reach-fast prototype fabrication and in vitro testing of innovative bi-leaflet valve models.

Science.gov (United States)

Scotten, Lawrence N; Siegel, Rolland

2015-08-01

Exploration for causes of prosthetic valve thrombogenicity has frequently focused on forward or post-closure flow detail. In prior laboratory studies, we uncovered high amplitude flow velocities of short duration close to valve closure implying potential for substantial shear stress with subsequent initiation of blood coagulation pathways. This may be relevant to widely accepted clinical disparity between mechanical and tissue valves vis-à-vis thrombogenicity. With a series of prototype bi-leaflet mechanical valves, we attempt reduction of closure related velocities with the objective of identifying a prototype valve with thrombogenic potential similar to our tissue valve control. This iterative design approach may find application in preclinical assessment of valves for anticoagulation independence. Tested valves included: prototype mechanical bi-leaflet BVs (n=56), controls (n=2) and patented early prototype mechanicals (n=2) from other investigators. Pulsatile and quasi-steady flow systems were used for testing. Projected dynamic valve area (PDVA) was measured using previously described novel technology. Flow velocity over the open and closing periods was determined by volumetric flow rate/PDVA. For the closed valve interval, use was made of data obtained from quasi-steady back pressure/flow tests. Performance was ranked by a proposed thrombogenicity potential index (TPI) relative to tissue and mechanical control valves. Optimization of the prototype valve designs lead to a 3-D printed model (BV3D). For the mitral/aortic site, BV3D has lower TPI (1.10/1.47) relative to the control mechanical valve (3.44/3.93) and similar to the control tissue valve (ideal TPI ≤1.0). Using unique technology, rapid prototyping and thrombogenicity ranking, optimization of experimental valves for reduced thrombogenic potential was expedited and simplified. Innovative mechanical valve configurations were identified that merit consideration for further development which may bring

Prosthetic Aortic Valve Fixation Study: 48 Replacement Valves Analyzed Using Digital Pressure Mapping.

Science.gov (United States)

Lee, Candice Y; Wong, Joshua K; Ross, Ronald E; Liu, David C; Khabbaz, Kamal R; Martellaro, Angelo J; Gorea, Heather R; Sauer, Jude S; Knight, Peter A

Prostheses attachment is critical in aortic valve replacement surgery, yet reliable prosthetic security remains a challenge. Accurate techniques to analyze prosthetic fixation pressures may enable the use of fewer sutures while reducing the risk of paravalvular leaks (PVL). Customized digital thin film pressure transducers were sutured between aortic annulus models and 21-mm bioprosthetic valves with 15 × 4-mm, 12 × 4-mm, or 9 × 6-mm-wide pledgeted mattress sutures. Simulating open and minimally invasive access, 4 surgeons, blinded to data acquisition, each secured 12 valves using manual knot-tying (hand-tied [HT] or knot-pusher [KP]) or automated titanium fasteners (TFs). Real-time pressure measurements and times were recorded. Two-dimensional (2D) and 3D pressure maps were generated for all valves. Pressures less than 80 mm Hg were considered at risk for PVL. Pressures under each knot (intrasuture) fell less than 80 mm Hg for 12 of 144 manual knots (5/144 HT, 7/144 KP) versus 0 of 288 TF (P prosthetic valve security.

Aortic valve function after bicuspidization of the unicuspid aortic valve.

Science.gov (United States)

Aicher, Diana; Bewarder, Moritz; Kindermann, Michael; Abdul-Khalique, Hashim; Schäfers, Hans-Joachim

2013-05-01

Unicuspid aortic valve (UAV) anatomy leads to dysfunction of the valve in young individuals. We introduced a reconstructive technique of bicuspidizing the UAV. Initially we copied the typical asymmetry of a normal bicuspid aortic valve (BAV) (I), later we created a symmetric BAV (II). This study compared the hemodynamic function of the two designs of a bicuspidized UAV. Aortic valve function was studied at rest and during exercise in 28 patients after repair of UAV (group I, n = 8; group II, n = 20). There were no differences among the groups I and II with respect to gender, age, body size, or weight. All patients were in New York Heart Association class I. Six healthy adults served as control individuals. All patients were studied with transthoracic echocardiography between 4 and 65 months postoperatively. Systolic gradients were assessed by continuous wave Doppler while patients were at rest and exercising on a bicycle ergometer. Aortic regurgitation was grade I or less in all patients. Resting gradients were significantly elevated in group I compared with group II and control individuals (group I, peak 33.8 ± 7.8 mm Hg; mean 19.1 ± 5.4 mm Hg; group II, peak 15.8 ± 5.4, mean 8.2 ± 2.8 mm Hg; control individuals, peak 6.0 ± 1.6, mean 3.2 ± 0.8 mm Hg; p competence. A symmetric repair design leads to improved systolic aortic valve function at rest and during exercise. Copyright © 2013 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

A nuclear radiation actuated valve for a nuclear reactor

International Nuclear Information System (INIS)

Christiansen, D.W.; Schively, D.P.

1983-01-01

The valve has a first part (such as a valve rod with piston) and a second part (such as a valve tube surrounding the valve rod, with the valve tube having side slots surrounding the piston). Both valve parts have known nuclear radiation swelling characteristics which are different. The valve parts are positioned so that the valve's first and second parts create a valve orifice which changes in size due to the different nuclear radiation caused swelling of the valve's first part compared to the valve's second part. The valve may be used in a nuclear reactor's core coolant system. (author)

Cavitation problems in sodium valves

International Nuclear Information System (INIS)

Elie, X.

1976-01-01

Cavitation poses few problems for sodium valves, in spite of the fact that the loops are not pressurized. This is no doubt due to the low flow velocities in the pipes. For auxiliary loop valves we are attempting to standardize performances with respect to cavitation. For economic reasons cavitation thresholds are approached with large diameter valves. (author)

Valve testing for UK PWR safety applications

International Nuclear Information System (INIS)

George, P.T.; Bryant, S.

1989-01-01

Extensive testing and development has been done by the Central Electricity Generating Board (CEGB) to support the design, construction and operation of Sizewell B, the UK's first PWR. A Blowdown Rig for the Assessment of Valve Operability - (BRAVO) has been constructed at the CEGB Marchwood Engineering Laboratory to reproduce PWR Pressurizer fluid conditions for the full scale testing of Pressurizer Relief System (PRS) valves. A full size tandem pair of Pilot Operated Safety Relief Valves (POSRVs) is being tested under the full range of pressurizer fluid conditions. Tests to date have produced important data on the performance of the valve in its Cold Overpressure protection mode of operation and on methods for the in-service testing of the valve. Also, a full size pressurizer safety valve has been tested under full PRS fluid conditions to develop a methodology for the pre-service testing of the Sizewell valves. Further work will be carried out to develop procedures for the in-service testing of the valve. In the Main Steam Safety Valve test program carried out at the Siemens-KWU Test Facilities, a single MSSV from three potential suppliers was tested under full secondary system conditions. The test results have been analyzed and are reflected in the CEGB's arrangements for the pre-service and in-service testing of the Sizewell MSSVs. Valves required to interrupt pipebreak flow must be qualified for this duty by testing or a combination of testing and analysis. To obtain guidance on the performance of such tests gate and globe valves have been subjected to simulated pipebreaks under PWR primary circuit conditions. In the light of problems encountered with gate valve closure under these conditions, further tests are currently being carried out on the BRAVO facility on a gate valve, in preparation for the full scale flow interruption qualification testing of the Sizewell main steam isolation valve

Krox20 defines a subpopulation of cardiac neural crest cells contributing to arterial valves and bicuspid aortic valve.

Science.gov (United States)

Odelin, Gaëlle; Faure, Emilie; Coulpier, Fanny; Di Bonito, Maria; Bajolle, Fanny; Studer, Michèle; Avierinos, Jean-François; Charnay, Patrick; Topilko, Piotr; Zaffran, Stéphane

2018-01-03

Although cardiac neural crest cells are required at early stages of arterial valve development, their contribution during valvular leaflet maturation remains poorly understood. Here, we show in mouse that neural crest cells from pre-otic and post-otic regions make distinct contributions to the arterial valve leaflets. Genetic fate-mapping analysis of Krox20-expressing neural crest cells shows a large contribution to the borders and the interleaflet triangles of the arterial valves. Loss of Krox20 function results in hyperplastic aortic valve and partially penetrant bicuspid aortic valve formation. Similar defects are observed in neural crest Krox20 -deficient embryos. Genetic lineage tracing in Krox20 -/- mutant mice shows that endothelial-derived cells are normal, whereas neural crest-derived cells are abnormally increased in number and misplaced in the valve leaflets. In contrast, genetic ablation of Krox20 -expressing cells is not sufficient to cause an aortic valve defect, suggesting that adjacent cells can compensate this depletion. Our findings demonstrate a crucial role for Krox20 in arterial valve development and reveal that an excess of neural crest cells may be associated with bicuspid aortic valve. © 2018. Published by The Company of Biologists Ltd.

Missed aortic valve endocarditis resulting in complete atrioventricular block and redo mechanical valve replacement.

Science.gov (United States)

Harky, Amer; Garner, Megan; Popa, Miruna; Shipolini, Alex

2017-08-03

Infective endocarditis is a rare disease associated with high morbidity and mortality. As a result, early diagnosis and prompt antibiotic treatment with or without surgical intervention is crucial in the management of such condition.We report a case of missed infective endocarditis of the aortic valve. The patient underwent mechanical aortic valve replacement, with the native valve being sent for histopathological examination. On re-admission 16 months later, he presented with syncope, shortness of breathing and complete heart block. On review of the histopathology of native aortic valve, endocarditis was identified which had not been acted on. The patient underwent redo aortic valve replacement for severe aortic regurgitation.We highlight the importance of following up histopathological results as well as the need for multidisciplinary treatment of endocarditis with a combination of surgical and antibiotic therapy. © BMJ Publishing Group Ltd (unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Improved corrosion resistance of spin-valve film

International Nuclear Information System (INIS)

Tetsukawa, H.; Hommura, H.; Okabe, A.; Soda, Y.

2007-01-01

We investigated the corrosion behavior and magnetoresistance of spin-valve film in order to improve the corrosion resistance of the spin-valve head for a tape recording system. The conventional spin-valve head (sub./Ta/NiFe/CoFe/Cu/CoFe/PtMn/Ta) with no diamond-like carbon (DLC) protective layer showed poor corrosion resistance. This is because the CoFe for ferromagnetic layer and Cu for spacer in the spin-valve film exhibited poor corrosion resistance. The corrosion resistance of the CoFe film and Cu film improved with the addition of Ni and Au, respectively. The spin-valve film (sub./Ta/NiFe/CoNiFe/CuAu/CoNiFe/PtMn/Ta) showed higher pitting potential than the conventional spin-valve film by +0.45 V. This presents a significant improvement over the conventional spin-valve film. We also investigated the effect of the composition of ferromagnetic layer and spacer on the magnetoresistance of the spin-valve film. The magnetoresistance of the spin-valve film by substitution of CoNiFe for CoFe in ferromagnetic layer decreased slightly. The magnetoresistance of the spin-valve film decreased as the addition of Au of the spacer increased. The diffusion at CoNiFe/CuAu interface has not been observed in annealing process. The quantitative relation between corrosion resistance and magnetoresistance of spin-valve film, and its ferromagnetic layer and spacer's compositions have been clarified. The output voltage at 50 Oe of the corrosion-resistant spin-valve head with CoNiFe ferromagnetic layer and CuAu spacer was about 50% of that of the conventional spin-valve head

Improved corrosion resistance of spin-valve film

Energy Technology Data Exchange (ETDEWEB)

Tetsukawa, H. [Sony Corporation, 6-7-35 Kitashinagawa, Shinagawa-ku, Tokyo 141-0001 (Japan)]. E-mail: tetsukaw@arc.sony.co.jp; Hommura, H. [Sony Corporation, 6-7-35 Kitashinagawa, Shinagawa-ku, Tokyo 141-0001 (Japan); Okabe, A. [Sony Corporation, 6-7-35 Kitashinagawa, Shinagawa-ku, Tokyo 141-0001 (Japan); Soda, Y. [Sony Corporation, 6-7-35 Kitashinagawa, Shinagawa-ku, Tokyo 141-0001 (Japan)

2007-06-15

We investigated the corrosion behavior and magnetoresistance of spin-valve film in order to improve the corrosion resistance of the spin-valve head for a tape recording system. The conventional spin-valve head (sub./Ta/NiFe/CoFe/Cu/CoFe/PtMn/Ta) with no diamond-like carbon (DLC) protective layer showed poor corrosion resistance. This is because the CoFe for ferromagnetic layer and Cu for spacer in the spin-valve film exhibited poor corrosion resistance. The corrosion resistance of the CoFe film and Cu film improved with the addition of Ni and Au, respectively. The spin-valve film (sub./Ta/NiFe/CoNiFe/CuAu/CoNiFe/PtMn/Ta) showed higher pitting potential than the conventional spin-valve film by +0.45 V. This presents a significant improvement over the conventional spin-valve film. We also investigated the effect of the composition of ferromagnetic layer and spacer on the magnetoresistance of the spin-valve film. The magnetoresistance of the spin-valve film by substitution of CoNiFe for CoFe in ferromagnetic layer decreased slightly. The magnetoresistance of the spin-valve film decreased as the addition of Au of the spacer increased. The diffusion at CoNiFe/CuAu interface has not been observed in annealing process. The quantitative relation between corrosion resistance and magnetoresistance of spin-valve film, and its ferromagnetic layer and spacer's compositions have been clarified. The output voltage at 50 Oe of the corrosion-resistant spin-valve head with CoNiFe ferromagnetic layer and CuAu spacer was about 50% of that of the conventional spin-valve head.

[Tricuspid valve insufficiency: what should be done?].

Science.gov (United States)

von Segesser, L K; Stauffer, J C; Delabays, A; Chassot, P G

1998-12-01

Tricuspid regurgitation is relatively common. Due to the progress made in echocardiography, its diagnosis is in general made readily and in reliable fashion. Basically one has to distinguish between functional tricuspid valve regurgitation due to volume and/or pressure overload of the right ventricle with intact valve structures versus tricuspid valve regurgitation due to pathologic valve structures. The clear identification of the regurgitation mechanism is of prime importance for the treatment. Functional tricuspid valve regurgitation can often be improved by medical treatment of heart failure, and eventually a tricuspid valve plasty can solve the problem. However, the presence of pathologic tricuspid valve structures makes in general more specific plastic surgical procedures and even prosthetic valve replacements necessary. A typical example for a structural tricuspid valve regurgitation is the case of a traumatic papillary muscle rupture. Due to the sudden onset, this pathology is not well tolerated and requires in general surgical reinsertion of the papillary muscle. In contrast, tricuspid valve regurgitation resulting from chronic pulmonary embolism with pulmonary artery hypertension, can be improved by pulmonary artery thrombendarteriectomy and even completely cured with an additional tricuspid annuloplasty. However, tricuspid regurgitations due to terminal heart failure are not be addressed with surgery directed to tricuspid valve repair or replacement. Heart transplantation, dynamic cardiomyoplasty or mechanical circulatory support should be evaluated instead.

Mitral valve surgery - open

Science.gov (United States)

... Taking warfarin (Coumadin) References Otto CM, Bonow RO. Valvular heart disease. In: Mann DL, Zipes DP, Libby P, Bonow ... A.M. Editorial team. Heart Surgery Read more Heart Valve Diseases Read more Mitral Valve Prolapse Read more A. ...

Check valves aging assessment

International Nuclear Information System (INIS)

Haynes, H.D.

1991-01-01

In support of the NRC Nuclear Plant Aging Research (NPAR) program, the Oak Ridge National Laboratory (ORNL) has carried out an assessment of several check value diagnostic monitoring methods, in particular, those based on measurements of acoustic emission, ultrasonics, and magnetic flux. The evaluations have focussed on the capabilities of each method to provide information useful in determining check valve aging and service wear effects, check valve failures, and undesirable operating modes. This paper describes the benefits and limitations associated with each method and includes recent laboratory and field test data, including data obtained from the vendors who recently participated in a comprehensive series of tests directed by a nuclear industry users group. In addition, as part of the ORNL Advanced Diagnostic Engineering Research and Development Center (ADEC), two novel nonintrusive monitoring methods were developed that provide several unique capabilities. These methods, based on external ac- an dc-magnetic monitoring are also described. None of the examined methods could, by themselves, monitor both the instantaneous position and motion of check valve internals and valve leakage; however, the combination of acoustic emission monitoring with one of the other methods provides the means to determine vital check valve operational information

Corrosion of valve metals

International Nuclear Information System (INIS)

Draley, J.E.

1976-01-01

A general survey related to the corrosion of valve metals or film-forming metals. The way these metals corrode with some general examples is described. Valve metals form relatively perfect oxide films with little breakdown or leakage when anodized

Echocardiographic Assessment of Heart Valve Prostheses

Science.gov (United States)

Sordelli, Chiara; Severino, Sergio; Ascione, Luigi; Coppolino, Pasquale; Caso, Pio

2014-01-01

Patients submitted to valve replacement with mechanical or biological prosthesis, may present symptoms related either to valvular malfunction or ventricular dysfunction from other causes. Because a clinical examination is not sufficient to evaluate a prosthetic valve, several diagnostic methods have been proposed to assess the functional status of a prosthetic valve. This review provides an overview of echocardiographic and Doppler techniques useful in evaluation of prosthetic heart valves. Compared to native valves, echocardiographic evaluation of prosthetic valves is certainly more complex, both for the examination and the interpretation. Echocardiography also allows discriminating between intra- and/or peri-prosthetic regurgitation, present in the majority of mechanical valves. Transthoracic echocardiography (TTE) requires different angles of the probe with unconventional views. Transesophageal echocardiography (TEE) is the method of choice in presence of technical difficulties. Three-dimensional (3D)-TEE seems to be superior to 2D-TEE, especially in the assessment of paravalvular leak regurgitation (PVL) that it provides improved localization and analysis of the PVL size and shape. PMID:28465917

3D Printed Multimaterial Microfluidic Valve.

Directory of Open Access Journals (Sweden)

Steven J Keating

Full Text Available We present a novel 3D printed multimaterial microfluidic proportional valve. The microfluidic valve is a fundamental primitive that enables the development of programmable, automated devices for controlling fluids in a precise manner. We discuss valve characterization results, as well as exploratory design variations in channel width, membrane thickness, and membrane stiffness. Compared to previous single material 3D printed valves that are stiff, these printed valves constrain fluidic deformation spatially, through combinations of stiff and flexible materials, to enable intricate geometries in an actuated, functionally graded device. Research presented marks a shift towards 3D printing multi-property programmable fluidic devices in a single step, in which integrated multimaterial valves can be used to control complex fluidic reactions for a variety of applications, including DNA assembly and analysis, continuous sampling and sensing, and soft robotics.

The radiology of prosthetic heart valves

International Nuclear Information System (INIS)

Steiner, R.M.; Flicker, S.

1985-01-01

The development of prosthetic heart valves in the late 1950s ushered in a new era in the treatment of heart disease. The radiologist has an important role to play preoperatively in the diagnosis of valvular heart disease. Radiology is valuable in identification of the implanted prosthetic valve and recognition of complications associated with valve implantation. Radiologists must be familiar with the imaging techniques best suited to evaluate the function of the valve prosthesis in question. In this chapter the authors discuss the radiographic approach to the evaluation of the status of patients for valve replacement and the imaging problems peculiar to the types of valves in current use. The relative value of plain-film radiography, fluoroscopy, videorecording and cinerecording, and aortography is addressed, as well as the potential value of magnetic resonance imaging and subsecond dynamic computed tomography

Valve system incorporating single failure protection logic

Science.gov (United States)

Ryan, Rodger; Timmerman, Walter J. H.

1980-01-01

A valve system incorporating single failure protective logic. The system consists of a valve combination or composite valve which allows actuation or de-actuation of a device such as a hydraulic cylinder or other mechanism, integral with or separate from the valve assembly, by means of three independent input signals combined in a function commonly known as two-out-of-three logic. Using the input signals as independent and redundant actuation/de-actuation signals, a single signal failure, or failure of the corresponding valve or valve set, will neither prevent the desired action, nor cause the undesired action of the mechanism.

All in the family: matrimonial mitral valve clicks.

Science.gov (United States)

Desser, K B; Bokhari, S I; Benchimol, A; Romney, D

1981-05-01

Mitral valve clicks with or without late systolic murmurs were detected in genetically unrelated marital partners of 5 families. The first family represented 2 successive nonconsanguineous marital unions with 3 generations of mitral valve clicks. The second family included 1 natural and 2 adopted children with clinical and echographic evidence of mitral valve prolapse. The third family was comprised of asymptomatic parents, both with nonejection clicks and mitral valve prolapse, whose daughter presented 3 years previously with syncope, palpitations, and combined mitral and tricuspid valve prolapse. The fourth family had 3 members with auscultatory and ultrasonic manifestations of billowing mitral valve, whereas the fourth member had "silent mitral valve prolapse." The fifth family represented a mother with auscultatory and echographic evidence of mitral valve prolapse; her 14-year-old daughter had both mitral and tricuspid valve prolapse, whereas the son had a bicuspid aortic valve. Both children were products of a prior marriage, and her husband has symptomatic mitral valve prolapse. We conclude that matrimonial mitral valve prolapse probably reflects the purported (6--10%) prevalence of this disorder in the general population. The consequences of such marital union on progeny is currently unclear and warrants future investigation.

Extended State Observer Based Adaptive Back-Stepping Sliding Mode Control of Electronic Throttle in Transportation Cyber-Physical Systems

Directory of Open Access Journals (Sweden)

Yongfu Li

2015-01-01

Full Text Available Considering the high accuracy requirement of information exchange via vehicle-to-vehicle (V2V communications, an extended state observer (ESO is designed to estimate the opening angle change of an electronic throttle (ET, wherein the emphasis is placed on the nonlinear uncertainties of stick-slip friction and spring in the system as well as the existence of external disturbance. In addition, a back-stepping sliding mode controller incorporating an adaptive control law is presented, and the stability and robustness of the system are analyzed using Lyapunov technique. Finally, numerical experiments are conducted using simulation. The results show that, compared with back-stepping control (BSC, the proposed controller achieves superior performance in terms of the steady-state error and rising time.

Echocardiographic evaluation of heart valve prosthetic dysfunction

Directory of Open Access Journals (Sweden)

Yuriy Ivaniv

2018-02-01

Full Text Available Patients with replaced heart valve submitted to echocardiographic examination may have symptoms related either to valvular malfunction or ventricular dysfunction from different causes. Clinical examination is not reliable in a prosthetic valve evaluation and the main information regarding its function could be obtained using different cardiac ultrasound modalities. This review provides a description of echocardiographic and Doppler techniques useful in evaluation of prosthetic heart valves. For the interpretation of echocardiography there is a need in special knowledge of prosthesis types and possible reasons of prosthetic function deterioration. Echocardiography allows to reveal valve thrombosis, pannus formation, vegetation and such complications of infective endocarditis as valve ring abscess or dehiscence. Transthoracic echocardiography requires different section plane angles and unconventional views. Transesophageal echocardiography is more often used than in native valve examination due to better visualization of prosthetic valve structure and function. Three-dimensional echocardiography could provide more detailed visual information especially in the assessment of paravalvular regurgitation or valve obstruction.

High-risk Trans-Catheter Aortic Valve Replacement in a Failed Freestyle Valve with Low Coronary Height: A Case Report.

Science.gov (United States)

Karimi, Ashkan; Pourafshar, Negiin; Dibu, George; Beaver, Thomas M; Bavry, Anthony A

2017-06-01

A 55-year-old male with a history of two prior cardiac surgeries presented with decompensated heart failure due to severe bioprosthetic aortic valve insufficiency. A third operation was viewed prohibitively high risk and valve-in-valve trans-catheter aortic valve replacement was considered. There were however several high-risk features and technically challenging aspects including low coronary ostia height, poor visualization of the aortic sinuses, and difficulty in identification of the coplanar view due to severe aortic insufficiency, and a highly mobile aortic valve mass. After meticulous peri-procedural planning, trans-catheter aortic valve replacement was carried out with a SAPIEN 3 balloon-expandable valve without any complication. Strategies undertaken to navigate the technically challenging aspects of the case are discussed.

Comparison of 3D Echocardiogram-Derived 3D Printed Valve Models to Molded Models for Simulated Repair of Pediatric Atrioventricular Valves.

Science.gov (United States)

Scanlan, Adam B; Nguyen, Alex V; Ilina, Anna; Lasso, Andras; Cripe, Linnea; Jegatheeswaran, Anusha; Silvestro, Elizabeth; McGowan, Francis X; Mascio, Christopher E; Fuller, Stephanie; Spray, Thomas L; Cohen, Meryl S; Fichtinger, Gabor; Jolley, Matthew A

2018-03-01

Mastering the technical skills required to perform pediatric cardiac valve surgery is challenging in part due to limited opportunity for practice. Transformation of 3D echocardiographic (echo) images of congenitally abnormal heart valves to realistic physical models could allow patient-specific simulation of surgical valve repair. We compared materials, processes, and costs for 3D printing and molding of patient-specific models for visualization and surgical simulation of congenitally abnormal heart valves. Pediatric atrioventricular valves (mitral, tricuspid, and common atrioventricular valve) were modeled from transthoracic 3D echo images using semi-automated methods implemented as custom modules in 3D Slicer. Valve models were then both 3D printed in soft materials and molded in silicone using 3D printed "negative" molds. Using pre-defined assessment criteria, valve models were evaluated by congenital cardiac surgeons to determine suitability for simulation. Surgeon assessment indicated that the molded valves had superior material properties for the purposes of simulation compared to directly printed valves (p 3D echo-derived molded valves are a step toward realistic simulation of complex valve repairs but require more time and labor to create than directly printed models. Patient-specific simulation of valve repair in children using such models may be useful for surgical training and simulation of complex congenital cases.

[Pannus Formation Six-years after Aortic and Mitral Valve Replacement with Tissue Valves;Report of a Case].

Science.gov (United States)

Nakamura, Makoto; Muraoka, Arata; Aizawa, Kei; Akutsu, Hirohiko; Kurumisawa, Soki; Misawa, Yoshio

2015-07-01

A 77-year-old man presented with exertional dyspnea. He had undergone aortic and mitral valve replacement with tissue valves 6-years earlier. The patient's hemoglobin level was 9.8 g/dl and serum aspartate aminotransferase (70 mU/ml) and lactate dehydrogenase (1,112 mU/ml) were elevated. Echocardiography revealed stenosis of the prosthetic valve in the aortic position with peak flow velocity of 3.8 m/second and massive mitral regurgitation. The patient underwent repeat valve replacement. Pannus formation around both implanted valves was observed. The aortic valve orifice was narrowed by the pannus, and one cusp of the prosthesis in the mitral position was fixed and caused the regurgitation, but they were free from cusp laceration or calcification. The patient's postoperative course was uneventful, and he continues to do well 14 months after surgery.

Safety valve opening and closing operation monitor

International Nuclear Information System (INIS)

Kodama, Kunio; Takeshima, Ikuo; Takahashi, Kiyokazu.

1981-01-01

Purpose: To enable the detection of the closing of a safety valve when the internal pressure in a BWR type reactor is a value which will close the safety valve, by inputting signals from a pressure detecting device mounted directly at a reactor vessel and a safety valve discharge pressure detecting device to an AND logic circuit. Constitution: A safety valve monitor is formed of a pressure switch mounted at a reactor pressure vessel, a pressure switch mounted at the exhaust pipe of the escape safety valve and a logic circuit and the lide. When the input pressure of the safety valve is raised so that the valve and the pressure switch mounted at the exhaust pipe are operated, an alarm is indicated, and the operation of the pressure switch mounted at a pressure vessel is eliminated. If the safety valve is not reclosed when the vessel pressure is decreased lower than the pressure at which it is to be reclosed after the safety valve is operated, an alarm is generated by the logic circuit since both the pressure switches are operated. (Sekiya, K.)

Determinants and outcomes of acute transcatheter valve-in-valve therapy or embolization: a study of multiple valve implants in the U.S. PARTNER trial (Placement of AoRTic TraNscathetER Valve Trial Edwards SAPIEN Transcatheter Heart Valve).

Science.gov (United States)

Makkar, Raj R; Jilaihawi, Hasan; Chakravarty, Tarun; Fontana, Gregory P; Kapadia, Samir; Babaliaros, Vasilis; Cheng, Wen; Thourani, Vinod H; Bavaria, Joseph; Svensson, Lars; Kodali, Susheel; Shiota, Takahiro; Siegel, Robert; Tuzcu, E Murat; Xu, Ke; Hahn, Rebecca T; Herrmann, Howard C; Reisman, Mark; Whisenant, Brian; Lim, Scott; Beohar, Nirat; Mack, Michael; Teirstein, Paul; Rihal, Charanjit; Douglas, Pamela S; Blackstone, Eugene; Pichard, Augusto; Webb, John G; Leon, Martin B

2013-07-30

This study investigated the determinants and outcomes of acute insertion of a second transcatheter prosthetic valve (TV) within the first (TV-in-TV) or transcatheter valve embolization (TVE) after transcatheter aortic valve replacement (TAVR). TAVR failure can occur with both TV-in-TV and TVE as a consequence of TAVR malpositioning. Only case reports and limited series pertaining to these complications have been reported to date. Patients undergoing TAVR in the PARTNER (Placement of AoRTic TraNscathetER Valve Trial Edwards SAPIEN Transcatheter Heart Valve) randomized trial (cohorts A and B) and accompanying registries were studied. Data were dichotomized for those with and without TV-in-TV or TVE, respectively. From a total of 2,554 consecutive patients, 63 (2.47%) underwent TV-in-TV and 26 (1.01%) TVE. The indication for TV-in-TV was significant aortic regurgitation in most patients, often due not only to malpositioning but also to leaflet dysfunction. Despite similar aortic valve function on follow-up echoes, TV-in-TV was an independent predictor of 1-year cardiovascular mortality (hazard ratio [HR]: 1.86, 95% confidence interval [CI]: 1.03 to 3.38, p = 0.041), with a nonsignificant trend toward greater all-cause mortality (HR: 1.43, 95% CI: 0.88 to 2.33, p = 0.15). Technical and anatomical reasons accounted for most cases of TVE. A multivariable analysis found TVE to be an independent predictor of 1-year mortality (HR: 2.68, 95% CI: 1.34 to 5.36, p = 0.0055) but not cardiovascular mortality (HR: 1.30, 95% CI: 0.48 to 3.52, p = 0.60). Acute TV-in-TV and TVE are serious sequelae of TAVR, often resulting in multiple valve implants. They carry an excess of mortality and are caused by anatomic and technical factors, which may be avoidable with judicious procedural planning. Copyright © 2013 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

Performance of balanced bellows safety relief valves

International Nuclear Information System (INIS)

Lai, Y.S.

1992-01-01

By the nature of its design, the set point and lift of a conventional spring loaded safety relief valve are sensitive to back pressure. One way to reduce the adverse effects of the back pressure on the safety relief valve function is to install a balanced bellows in a safety relief valve. The metallic bellows has a rather wide range of manufacturing tolerance which makes the design of the bellows safety relief valve very complicated. The state-of-the-art balanced bellows safety relief valve can only substantially minimize, but cannot totally eliminate the back pressure effects on its set point and relieving capacity. Set point change is a linear function of the back pressure to the set pressure ratio. Depending on the valve design, the set point correction factor can be either greater or smaller than unity. There exists an allowable back pressure and critical back pressure for each safety relief valve. When total back pressure exceeds the R a , the relieving capacity will be reduced mainly resulting from the valve lift being reduced by the back pressure and the capacity reduction factor should be applied in valve sizing. Once the R c is exceeded, the safety relief valve becomes unstable and loses its over pressure protection capability. The capacity reduction factor is a function of system overpressure, but their relationship is non-linear in nature. (orig.)

Hydraulic engine valve actuation system including independent feedback control

Science.gov (United States)

Marriott, Craig D

2013-06-04

A hydraulic valve actuation assembly may include a housing, a piston, a supply control valve, a closing control valve, and an opening control valve. The housing may define a first fluid chamber, a second fluid chamber, and a third fluid chamber. The piston may be axially secured to an engine valve and located within the first, second and third fluid chambers. The supply control valve may control a hydraulic fluid supply to the piston. The closing control valve may be located between the supply control valve and the second fluid chamber and may control fluid flow from the second fluid chamber to the supply control valve. The opening control valve may be located between the supply control valve and the second fluid chamber and may control fluid flow from the supply control valve to the second fluid chamber.

Implante valve-in-valve transcateter em posição aórtica: uma mudança de seleção? Transcatheter aortic valve-in-valve implantation: a selection change?

Directory of Open Access Journals (Sweden)

Diego Felipe Gaia

2012-09-01

Full Text Available INTRODUÇÃO: A reoperação para substituição de biopróteses aórticas com disfunção é procedimento que envolve considerável risco. Em alguns casos, a mortalidade é elevada e pode contraindicar o procedimento. O implante minimamente invasivo "valve-in-valve" transcateter de valva aórtica parece ser uma alternativa, reduzindo morbimortalidade. O objetivo deste estudo foi avaliar esses implantes utilizando a prótese Braile Inovare. MÉTODOS: A prótese Braile Inovare, transcateter, balão expansível foi utilizada em 14 casos. Euroscore médio foi de 42,9%. Todos os pacientes eram portadores de dupla disfunção de bioprótese aórtica. Os procedimentos foram realizados em ambiente cirúrgico híbrido, sob controle ecocardiográfico e fluoroscópico. Por meio de minitoracotomia esquerda, as próteses foram implantadas através do ápice ventricular, sob estimulação ventricular de alta frequência. Foram realizados controles clínicos e ecocardiográficos seriados. O seguimento variou de 1 a 30 meses. RESULTADOS: A correta liberação protética foi possível em todos os casos. Não ocorreu conversão. Não houve mortalidade operatória. A mortalidade em 30 dias foi de 14,3% (dois casos. A fração de ejeção apresentou aumento significativo após o 7º pós-operatório e o gradiente aórtico apresentou redução significativa. A insuficiência aórtica residual não esteve presente. Não ocorreu complicação vascular periférica ou bloqueio atrioventricular total. CONCLUSÕES: O implante "valve-in-valve" de valva aórtica transcateter em biopróteses com disfunção é um procedimento seguro e com morbimortalidade baixa. Essa possibilidade poderá alterar a indicação de seleção de prótese no procedimento inicial, favorecendo próteses biológicas.OBJECTIVE: Aortic valve replacement for bioprosthesis dysfunction is a procedure involving considerable risk. In some cases, mortality is high and may contraindicate the procedure

[Ahmed valve in glaucoma surgery].

Science.gov (United States)

Bikbov, M M; Khusnitdinov, I I

This is a review on Ahmed valve application in glaucoma surgery. It contains, in particular, data on the Ahmed valve efficiency, results of experimental and histological studies of filtering bleb encapsulation, examines the use of antimetabolites and anti-VEGF agents, and discusses implantation techniques. The current appraisal of antimetabolites delivery systems integrated into the Ahmed valve is presented. Various complications encountered in practice and preventive measures are also covered.

GIANT PROSTHETIC VALVE THROMBUS

Directory of Open Access Journals (Sweden)

Prashanth Kumar

2015-04-01

Full Text Available Mechanical prosthetic valves are predisposed to bleeding, thrombosis & thromboembolic complications. Overall incidence of thromboembolic complications is 1% per year who are on oral anticoagulants, whereas bleeding complications incidence is 0.5% to 6.6% per year. 1, 2 Minimization of Scylla of thromboembolic & Charybdis of bleeding complication needs a balancing act of optimal antithrombotic therapy. We are reporting a case of middle aged male patient with prosthetic mitral valve presenting in heart failure. Patient had discontinued anticoagulants, as he had subdural hematoma in the past. He presented to our institute with a giant prosthetic valve thrombus.

Bicuspid aortic valves: Diagnostic accuracy of standard axial 64-slice chest CT compared to aortic valve image plane ECG-gated cardiac CT

Energy Technology Data Exchange (ETDEWEB)

Murphy, David J., E-mail: david.murphy@st-vincents.ie [Department of Radiology, St Vincent' s University Hospital, Elm Park, Dublin 4 (Ireland); McEvoy, Sinead H., E-mail: s.mcevoy@st-vincents.ie [Department of Radiology, St Vincent' s University Hospital, Elm Park, Dublin 4 (Ireland); Iyengar, Sri, E-mail: sri.iyengar@nhs.net [Department of Radiology, Plymouth Hospitals NHS Trust, Plymouth Devon PL6 8DH (United Kingdom); Feuchtner, Gudrun, E-mail: Gudrun.Feuchtner@i-med.ac.at [Department of Radiology, Innsbruck Medical University, Anichstr. 35, A-6020 Innsbruck (Austria); Cury, Ricardo C., E-mail: r.cury@baptisthealth.net [Department of Radiology, Baptist Cardiac and Vascular Institute, 8900 North Kendall Drive, Miami, FL 33176 (United States); Roobottom, Carl, E-mail: carl.roobottom@nhs.net [Department of Radiology, Plymouth Hospitals NHS Trust, Plymouth Devon PL6 8DH (United Kingdom); Plymouth University Peninsula Schools of Medicine and Dentistry (United Kingdom); Baumueller, Stephan, E-mail: Hatem.Alkadhi@usz.ch [Institute for Diagnostic and Interventional Radiology, University Hospital Zurich, Raemistrasse 100, CH-8091 Zurich (Switzerland); Alkadhi, Hatem, E-mail: stephan.baumueller@usz.ch [Institute for Diagnostic and Interventional Radiology, University Hospital Zurich, Raemistrasse 100, CH-8091 Zurich (Switzerland); Dodd, Jonathan D., E-mail: jonniedodd@gmail.com [Department of Radiology, St Vincent' s University Hospital, Elm Park, Dublin 4 (Ireland)

2014-08-15

Objectives: To assess the diagnostic accuracy of standard axial 64-slice chest CT compared to aortic valve image plane ECG-gated cardiac CT for bicuspid aortic valves. Materials and methods: The standard axial chest CT scans of 20 patients with known bicuspid aortic valves were blindly, randomly analyzed for (i) the appearance of the valve cusps, (ii) the largest aortic sinus area, (iii) the longest aortic cusp length, (iv) the thickest aortic valve cusp and (v) valve calcification. A second blinded reader independently analyzed the appearance of the valve cusps. Forty-two age- and sex-matched patients with known tricuspid aortic valves were used as controls. Retrospectively ECG-gated cardiac CT multiphase reconstructions of the aortic valve were used as the gold-standard. Results: Fourteen (21%) scans were scored as unevaluable (7 bicuspid, 7 tricuspid). Of the remainder, there were 13 evaluable bicuspid valves, ten of which showed an aortic valve line sign, while the remaining three showed a normal Mercedes-Benz appearance owing to fused valve cusps. The 35 evaluable tricuspid aortic valves all showed a normal Mercedes-Benz appearance (P = 0.001). Kappa analysis = 0.62 indicating good interobserver agreement for the aortic valve cusp appearance. Aortic sinus areas, aortic cusp lengths and aortic cusp thicknesses of ≥3.8 cm{sup 2}, 3.2 cm and 1.6 mm respectively on standard axial chest CT best distinguished bicuspid from tricuspid aortic valves (P < 0.0001 for all). Of evaluable scans, the sensitivity, specificity, positive and negative predictive values of standard axial chest CT in diagnosing bicuspid aortic valves was 77% (CI 0.54–1.0), 100%, 100% and 70% respectively. Conclusion: The aortic valve is evaluable in approximately 80% of standard chest 64-slice CT scans. Bicuspid aortic valves may be diagnosed on evaluable scans with good diagnostic accuracy. An aortic valve line sign, enlarged aortic sinuses and elongated, thickened valve cusps are specific CT

Minimally invasive aortic valve replacement

DEFF Research Database (Denmark)

Foghsgaard, Signe; Schmidt, Thomas Andersen; Kjaergard, Henrik K

2009-01-01

In this descriptive prospective study, we evaluate the outcomes of surgery in 98 patients who were scheduled to undergo minimally invasive aortic valve replacement. These patients were compared with a group of 50 patients who underwent scheduled aortic valve replacement through a full sternotomy...... operations were completed as mini-sternotomies, 4 died later of noncardiac causes. The aortic cross-clamp and perfusion times were significantly different across all groups (P replacement...... is an excellent operation in selected patients, but its true advantages over conventional aortic valve replacement (other than a smaller scar) await evaluation by means of randomized clinical trial. The "extended mini-aortic valve replacement" operation, on the other hand, is a risky procedure that should...

MEMS Micro-Valve for Space Applications

Science.gov (United States)

Chakraborty, I.; Tang, W. C.; Bame, D. P.; Tang, T. K.

1998-01-01

We report on the development of a Micro-ElectroMechanical Systems (MEMS) valve that is designed to meet the rigorous performance requirements for a variety of space applications, such as micropropulsion, in-situ chemical analysis of other planets, or micro-fluidics experiments in micro-gravity. These systems often require very small yet reliable silicon valves with extremely low leak rates and long shelf lives. Also, they must survive the perils of space travel, which include unstoppable radiation, monumental shock and vibration forces, as well as extreme variations in temperature. Currently, no commercial MEMS valve meets these requirements. We at JPL are developing a piezoelectric MEMS valve that attempts to address the unique problem of space. We begin with proven configurations that may seem familiar. However, we have implemented some major design innovations that should produce a superior valve. The JPL micro-valve is expected to have an extremely low leak rate, limited susceptibility to particulates, vibration or radiation, as well as a wide operational temperature range.

Radiological visualization of prosthetic heart valves in situ

International Nuclear Information System (INIS)

Hoffmeister, H.M.; Pirschel, J.

1986-01-01

To determine the radiographic appearance of prosthetic heart valves 15 different models were investigated in situ. Fluoroscopy with detail radiographs and standard chest-radiographs were used for identification of the specific type of the prosthesis, for determination of details of the valve apparatus and for evaluation of the motion of the valve disc/ball. - Fluoroscopy and routine radiographs provided sufficient information to identify all prosthetic heart valves with exception of the Xenomedica bioprosthesis. If radiopaque material was used for the valve disc/ball, fluoroscopic assessment of the function of the valve was possible. Thus, in most types of disc or ball valves the opening/closing of the valve can be visualized, whereas in bioprosthesis a radiological determination of the mechanical function is not possible. (orig.) [de

Non intrusive check valve diagnostics at Bruce A

International Nuclear Information System (INIS)

Marsch, S.P.

1997-01-01

Bruce A purchased non intrusive check valve diagnostic equipment in 1995 to ensure operability and availability of critical check valves in the Station. Diagnostics can be used to locate and monitor check valve degradation modes. Bruce A initiated a pilot program targeting check valves with flow through them and ones that completed open or close cycles. Approaches to determine how to confirm operability of passive check valves using non intrusive techniques were explored. A sample population of seventy-three check valves was selected to run the pilot program on prior to complete implementation. The pilot program produced some significant results and some inconclusive results. The program revealed a major finding that check valve performance modeling is required to ensure continuous operability of check valves. (author)

Non intrusive check valve diagnostics at Bruce A

Energy Technology Data Exchange (ETDEWEB)

Marsch, S.P. [Ontario Hydro, Bruce Nuclear Generating Station A, Tiverton, ON (Canada)

1997-07-01

Bruce A purchased non intrusive check valve diagnostic equipment in 1995 to ensure operability and availability of critical check valves in the Station. Diagnostics can be used to locate and monitor check valve degradation modes. Bruce A initiated a pilot program targeting check valves with flow through them and ones that completed open or close cycles. Approaches to determine how to confirm operability of passive check valves using non intrusive techniques were explored. A sample population of seventy-three check valves was selected to run the pilot program on prior to complete implementation. The pilot program produced some significant results and some inconclusive results. The program revealed a major finding that check valve performance modeling is required to ensure continuous operability of check valves. (author)

Danfos: Thermostatic Radiator Valves

DEFF Research Database (Denmark)

Gregersen, Niels; Oliver, James; Hjorth, Poul G.

2000-01-01

This problem deals with modelling the flow through a typical Danfoss thermostatic radiator valve.Danfoss is able to employ Computational Fluid Dynamics (CFD) in calculations of the capacity of valves, but an experienced engineer can often by rules of thumb "guess" the capacity, with a precision...

Recurrent pannus formation causing prosthetic aortic valve dysfunction: Is excision without valve re-replacement applicable?

OpenAIRE

Darwazah Ahmad K

2012-01-01

Abstract Prosthetic valve dysfunction at aortic position is commonly caused by pannus formation. The exact etiology is not known. It arises from ventricular aspect of the prosthesis encroaching its leaflets causing stenosis or it may remain localized causing left ventricular outflow tract obstruction without affecting valve function. The difference in location entails different approaches in management. Such a pathology requires surgical excision of the pannus with or without valve re-replace...

Risk Factors for Late Aortic Valve Dysfunction After the David V Valve-Sparing Root Replacement.

Science.gov (United States)

Esaki, Jiro; Leshnower, Bradley G; Binongo, Jose N; Lasanajak, Yi; McPherson, LaRonica; Guyton, Robert A; Chen, Edward P

2017-11-01

Valve-sparing root replacement (VSRR) is an established therapy for aortic root pathology. However, late aortic valve dysfunction requiring reoperation remains a primary concern of this procedure. This study examines risk factors for late aortic insufficiency (AI) and aortic stenosis (AS) after David V VSRR. A retrospective review from 2005 to 2015 at a US academic center identified 282 patients who underwent VSRR. Cox proportional hazards regression analysis was used to identify risk factors for late AI and AS after VSRR. The mean age was 46.4 years. Sixty-four patients (22.7%) had bicuspid valves, and 41 patients (14.5%) had Marfan syndrome. The incidence of reoperations was 27 (9.6%), and 42 cases (14.9%) presented with acute type A dissection. Operative mortality was 8 (2.8%). Seven-year survival was 90.9%. Seven-year cumulative incidence of reoperation, greater than 2+ AI and greater than moderate AS were 3.1%, 2.2%, and 0.8%, respectively. Multivariable analysis showed aortic root size 55 mm or larger (hazard ratio 3.44, 95% confidence interval: 1.27 to 9.29, p = 0.01) to be a risk factor for late AI whereas bicuspid valve (hazard ratio 16.07, 95% confidence interval: 3.12 to 82.68, p = 0.001) and cusp repair were found to be risk factors (hazard ratio 5.91, 95% confidence interval: 1.17 to 29.86, p = 0.03) for late AS. Valve-sparing root replacement can be performed with low operative risk and good overall long-term survival even in complex clinical settings. Durable valve function can be expected; however, aortic root size 55 cm or more, bicuspid valve anatomy, and cusp repair represent independent risk factors for late aortic valve dysfunction after these procedures. Copyright © 2017 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

Safety valve including a hydraulic brake and hydraulic brake that could be fitted into a valve

International Nuclear Information System (INIS)

Chabat-Courrede, Jean.

1981-01-01

Making of a safety valve that can be fitted to a containment vessel filled with a non compressible fluid, such as the water system of a nuclear power station. It includes a hydraulic brake located between the valve and the elastic means, close to the valve which completely suppresses the high frequency oscillations of the equipment [fr

49 CFR 229.109 - Safety valves.

Science.gov (United States)

2010-10-01

... 49 Transportation 4 2010-10-01 2010-10-01 false Safety valves. 229.109 Section 229.109..., DEPARTMENT OF TRANSPORTATION RAILROAD LOCOMOTIVE SAFETY STANDARDS Safety Requirements Steam Generators § 229.109 Safety valves. Every steam generator shall be equipped with at least two safety valves that have a...

Automatic fire hydrant valve development

International Nuclear Information System (INIS)

Drumheller, K.

1976-01-01

The development of a remotely-controlled valve to operate a fire hydrant is described. Assembled from off-the-shelf components, the prototype illustrates that a valve light enough to be handled by one man is possible. However, it does not have the ruggedness or reliability needed for actual fire-fighting operations. Preliminary testing by City of Tacoma fire department personnel indicates that the valve may indeed contribute significantly to fire-fighting efficiency

Valve and dash-pot assembly

Science.gov (United States)

Chang, Shih-Chih

1986-01-01

A dash-pot valve comprising a cylinder submerged in the fluid of a housing and having a piston attached to a plunger projecting into the path of closing movement of a pivotal valve member. A vortex chamber in said cylinder is provided with tangentially directed inlets to generate vortex flow upon retraction of said plunger and effect increasing resistance against said piston to progressively retard the closing rate of said valve member toward its seat.

Operating experience and design criteria of sodium valves

International Nuclear Information System (INIS)

Markford, D.

1974-01-01

The information presented refers to sodium valve development for KNK and SNR-300 as well as for sodium test facilities on the INTERATOM site at Bensberg. Well in advance of KNK-I a number of sodium test facilities have been operated containing small and medium size valves of different design and manufacturer. The more stringent requirements for long range safe and reliable operation in KNK-I put forth a development program for the main primary and secondary circuit sodium valves. Operational experience gave rise to modification of the stem seal arrangement mainly, so KNK-II (which is the fast core for KNK reactor) will be run with modified sodium valves. Main pipe diameters in SNR-300 are in the range of 600 mm. Valve designs with rising shafts would require excessive space in the primary circuit cavities, therefore efforts have been directed towards introduction of different type valves. Due to the requirements of after-heat-removal a valve type with control capability had to be chosen. A special design of butterfly valves was selected for the primary and secondary circuits of SNR-300. The development and tests performed with this type of valve are described. In the field of small sodium valves, tests with a 50 mm diameter freeze-seal valve are reported, and the current status of bellows-seal-valves to be inserted into SNR-300 is discussed. (U.S.)

Acoustic valve leak detection in nuclear plants

International Nuclear Information System (INIS)

Dimmick, J.G.; Dickey, J.W.

1983-01-01

Internal valve leakage is a hidden energy loss and can cause or prolong a forced outage. Recent advances in acoustic detection of internal valve leakage have reduced piping system maintenance costs, unnecessary downtime, and energy waste. Extremely short payback periods have been reported by plants applying this technology to preventive maintenance, troubleshooting, energy conservation and outage planning. Sensors temporarily attached to the outside of valves and connected to the instruments detect ultrasonic acoustic emissions which are characteristic of internal valve leakage. Since the sensors are attached to the outside of the valves, the time and expense of dismantling the valves or removing them from the systems are eliminated. This paper describes the instrumentation and specific applications to nuclear plant valves, including independent verification of initial findings. Guidelines for potential users, including instrumentation selection, training requirements, application planning, and the choice of in-house versus contract services are discussed

Valve selection handbook engineering fundamentals for selecting the right valve design for every industrial flow application

CERN Document Server

Smith, Peter

2004-01-01

Valves are the components in a fluid flow or pressure system that regulate either the flow or the pressure of the fluid. They are used extensively in the process industries, especially petrochemical. Though there are only four basic types of valves, there is an enormous number of different kinds of valves within each category, each one used for a specific purpose. No other book on the market analyzes the use, construction, and selection of valves in such a comprehensive manner.-Covers new environmentally-conscious equipment and practices, the most important hot-button issue in the p

Experience with control valve cavitation problems and their solutions

International Nuclear Information System (INIS)

Ozol, J.

1988-01-01

Pressure reduction in control valves can induce cavitation, which has three effects on the control valve. Firstly, it modifies or changes the hydraulic performance of the control valve. Since control valves are designed for noncavitating conditions, the result is usually reduced stability of the control valve or, in extreme cavitating conditions known as supercavitation, the valve may limit the flow rate and thus be undersized. Secondly, cavitation can cause material damage to valve parts, trim, or valve body, or erodes downstream piping; consequently, the valve or piping leaks. Thirdly, cavitation causes noise and vibration, which may cause major damage or destruction to equipment such as valve positioners, actuators, pipe supports and sometimes to other downstream valves. The purpose of this paper is twofold: (1) It describes the I.S.A. valve sizing equations and how they relate to cavitation. (2) It describes experiences with these three problems, and discusses corrective actions and practical approaches to their solution. This paper discusses thirteen cavitation experiences

Control valve friction operational experience at Darlington NGD

International Nuclear Information System (INIS)

Speer, B.

1995-01-01

Proper installation of valve packing is an important part of ensuring that control valves operate as intended. Darlington NGD has developed a Valve Packing Program. This program combined with valve diagnostics has enabled the station to ensure that the operability of control valves is maintained after repacking. This paper outlines the process that is used for this. (author)

An application of the valve-leak monitoring system to the valves for the improved Korean standard nuclear power plant (KSNP+)

International Nuclear Information System (INIS)

Byeong-yeol AHN; Dae-sik CHOI; Sang-kook CHUNG

2006-01-01

The loss of steam due to valve leakage leads to the inefficiency of power generation at the nuclear power plants. Under the normal conditions of plant operation, it is difficult to detect valve leaks early enough to prevent consequential damages and losses. The capability of timely detection allows the plant adequate time to prepare repair plans, which would ultimately result in efficient power production. Therefore, timing of detection is one of the most important factors in dealing with valve leakage problems. The VLMS has been developed to meet such an industrial demand. It provides early detection of valve leakage by real-time monitoring through the acoustic sensors installed on the inlet and the outlet of the valve. The KSNP+ utilizes the VLMS to enhance the performance and maintenance of major valves at plants. The VLMS will enable the plant to detect the leakage of valve at an early stage. It can reduce the steam losses and save related valve maintenance cost by performing fast diagnosis of valve leakage. (authors)

Technical evaluation: 300 Area steam line valve accident

International Nuclear Information System (INIS)

1993-08-01

On June 7, 1993, a journeyman power operator (JPO) was severely burned and later died as a result of the failure of a 6-in. valve that occurred when he attempted to open main steam supply (MSS) valve MSS-25 in the U-3 valve pit. The pit is located northwest of Building 331 in the 300 Area of the Hanford Site. Figure 1-1 shows a layout of the 300 Area steam piping system including the U-3 steam valve pit. Figure 1-2 shows a cutaway view of the approximately 10- by 13- by 16-ft-high valve pit with its various steam valves and connecting piping. Valve MSS-25, an 8-in. valve, is located at the bottom of the pit. The failed 6-in. valve was located at the top of the pit where it branched from the upper portion of the 8-in. line at the 8- by 8- by 6-in. tee and was then ''blanked off'' with a blind flange. The purpose of this technical evaluation was to determine the cause of the accident that led to the failure of the 6-in. valve. The probable cause for the 6-in. valve failure was determined by visual, nondestructive, and destructive examination of the failed valve and by metallurgical analysis of the fractured region of the valve. The cause of the accident was ultimately identified by correlating the observed failure mode to the most probable physical phenomenon. Thermal-hydraulic analyses, component stress analyses, and tests were performed to verify that the probable physical phenomenon could be reasonably expected to produce the failure in the valve that was observed

Statins for aortic valve stenosis

Directory of Open Access Journals (Sweden)

Luciana Thiago

Full Text Available ABSTRACT BACKGROUND: Aortic valve stenosis is the most common type of valvular heart disease in the USA and Europe. Aortic valve stenosis is considered similar to atherosclerotic disease. Some studies have evaluated statins for aortic valve stenosis. OBJECTIVES: To evaluate the effectiveness and safety of statins in aortic valve stenosis. METHODS: Search methods: We searched the Cochrane Central Register of Controlled Trials (CENTRAL, MEDLINE, Embase, LILACS - IBECS, Web of Science and CINAHL Plus. These databases were searched from their inception to 24 November 2015. We also searched trials in registers for ongoing trials. We used no language restrictions. Selection criteria: Randomized controlled clinical trials (RCTs comparing statins alone or in association with other systemic drugs to reduce cholesterol levels versus placebo or usual care. Data collection and analysis: Primary outcomes were severity of aortic valve stenosis (evaluated by echocardiographic criteria: mean pressure gradient, valve area and aortic jet velocity, freedom from valve replacement and death from cardiovascular cause. Secondary outcomes were hospitalization for any reason, overall mortality, adverse events and patient quality of life. Two review authors independently selected trials for inclusion, extracted data and assessed the risk of bias. The GRADE methodology was employed to assess the quality of result findings and the GRADE profiler (GRADEPRO was used to import data from Review Manager 5.3 to create a 'Summary of findings' table. MAIN RESULTS: We included four RCTs with 2360 participants comparing statins (1185 participants with placebo (1175 participants. We found low-quality evidence for our primary outcome of severity of aortic valve stenosis, evaluated by mean pressure gradient (mean difference (MD -0.54, 95% confidence interval (CI -1.88 to 0.80; participants = 1935; studies = 2, valve area (MD -0.07, 95% CI -0.28 to 0.14; participants = 127; studies = 2

Statins for aortic valve stenosis.

Science.gov (United States)

Thiago, Luciana; Tsuji, Selma Rumiko; Nyong, Jonathan; Puga, Maria Eduarda Dos Santos; Góis, Aécio Flávio Teixeira de; Macedo, Cristiane Rufino; Valente, Orsine; Atallah, Álvaro Nagib

2016-01-01

Aortic valve stenosis is the most common type of valvular heart disease in the USA and Europe. Aortic valve stenosis is considered similar to atherosclerotic disease. Some studies have evaluated statins for aortic valve stenosis. To evaluate the effectiveness and safety of statins in aortic valve stenosis. Search methods: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, LILACS - IBECS, Web of Science and CINAHL Plus. These databases were searched from their inception to 24 November 2015. We also searched trials in registers for ongoing trials. We used no language restrictions.Selection criteria: Randomized controlled clinical trials (RCTs) comparing statins alone or in association with other systemic drugs to reduce cholesterol levels versus placebo or usual care. Data collection and analysis: Primary outcomes were severity of aortic valve stenosis (evaluated by echocardiographic criteria: mean pressure gradient, valve area and aortic jet velocity), freedom from valve replacement and death from cardiovascular cause. Secondary outcomes were hospitalization for any reason, overall mortality, adverse events and patient quality of life.Two review authors independently selected trials for inclusion, extracted data and assessed the risk of bias. The GRADE methodology was employed to assess the quality of result findings and the GRADE profiler (GRADEPRO) was used to import data from Review Manager 5.3 to create a 'Summary of findings' table. We included four RCTs with 2360 participants comparing statins (1185 participants) with placebo (1175 participants). We found low-quality evidence for our primary outcome of severity of aortic valve stenosis, evaluated by mean pressure gradient (mean difference (MD) -0.54, 95% confidence interval (CI) -1.88 to 0.80; participants = 1935; studies = 2), valve area (MD -0.07, 95% CI -0.28 to 0.14; participants = 127; studies = 2), and aortic jet velocity (MD -0.06, 95% CI -0.26 to 0

Miniature piezo electric vacuum inlet valve

Science.gov (United States)

Keville, Robert F.; Dietrich, Daniel D.

1998-03-24

A miniature piezo electric vacuum inlet valve having a fast pulse rate and is battery operated with variable flow capability. The low power (piezo electric valves which require preloading of the crystal drive mechanism and 120 Vac, thus the valve of the present invention is smaller by a factor of three.

Bentall Operation with Valved Homograft Conduit

Science.gov (United States)

Choudhary, Shiv K.; Talwar, Sachin; Kumar, A. Sampath

2000-01-01

Lesions of the ascending aorta associated with aortic valve disease are usually treated by implanting a prosthetic valved conduit (Bentall procedure). In this report, we present our experience in which a valved homograft conduit was used for the procedure. Six patients underwent a Bentall procedure with the use of a cryopreserved valved homograft conduit. Two of the patients had annuloaortic ectasia, 2 had Marfan syndrome, and 1 had an atherosclerotic aneurysm of the aorta. One patient had severe aortic stenosis due to a bicuspid aortic valve, along with an aneurysm and localized dissection of the ascending aorta. In all of the patients, the aortic annulus was substantially dilated, with accompanying moderate-to-severe aortic regurgitation. A standard procedure was performed with moderate hypothermia, cardiopulmonary bypass, and aortic and bicaval cannulation. The ascending aorta and the aortic valve were replaced with a cryopreserved valved homograft conduit (aortic in 5 patients and pulmonary in 1). The native coronary ostia were anastomosed directly to the homograft. Echocardiography, which was performed intraoperatively, before discharge from the hospital, and at follow-up visits (1 to 36 months), revealed good valve function without dilatation of the homograft conduits. There was 1 late death due to Aspergillus fumigatus endocarditis, 6 months postoperatively. In 1 patient, magnetic resonance imaging performed at 24 months revealed normal caliber of the homograft conduit. We conclude that the Bentall procedure can be performed, safely and with excellent results, using cryopreserved homograft conduits. PMID:11198310

New-Onset Atrial Fibrillation After Surgical Aortic Valve Replacement and Transcatheter Aortic Valve Implantation

DEFF Research Database (Denmark)

Jørgensen, Troels Højsgaard; Thygesen, Julie Bjerre; Thyregod, Hans Gustav

2015-01-01

Surgical aortic valve replacement (SAVR) and, more recently, transcatheter aortic valve implantation (TAVI) have been shown to be the only treatments that can improve the natural cause of severe aortic valve stenosis. However, after SAVR and TAVI, the incidence of new-onset atrial fibrillation...... (NOAF) is 31%-64% and 4%-32%, respectively. NOAF is independently associated with adverse events such as stroke, death, and increased length of hospital stay. Increasing the knowledge of predisposing factors, optimal postprocedural monitoring, and prophylactic antiarrhythmic and antithrombotic therapy...

New-onset atrial fibrillation after surgical aortic valve replacement and transcatheter aortic valve implantation

DEFF Research Database (Denmark)

Jørgensen, Troels Højsgaard; Thygesen, Julie Bjerre; Thyregod, Hans Gustav

2015-01-01

Surgical aortic valve replacement (SAVR) and, more recently, transcatheter aortic valve implantation (TAVI) have been shown to be the only treatments that can improve the natural cause of severe aortic valve stenosis. However, after SAVR and TAVI, the incidence of new-onset atrial fibrillation...... (NOAF) is 31%-64% and 4%-32%, respectively. NOAF is independently associated with adverse events such as stroke, death, and increased length of hospital stay. Increasing the knowledge of predisposing factors, optimal postprocedural monitoring, and prophylactic antiarrhythmic and antithrombotic therapy...

The use of valves in the SAGD process

Energy Technology Data Exchange (ETDEWEB)

Romano, Michael A. [Global Marketing, Oil and Gas, Tyco Valves and Controls (United States)

2011-07-01

Steam-assisted gravity drainage (SAGD) is a developing technology, the aim of which is to increase production of bitumen while minimizing its environmental footprint. Valves must meet the process conditions of the operations, which depend on weel depth: deeper reservoirs of bitumen require higher steam injection pressure. A wide range of valves is used throughout the SAGD process. In the water softening plant, butterfly and process lined valves are used. HP gate valves are used for isolation, globe valves for vents/drains/bypasses, along with ARC valves for steam and booster pump projection with steam traps on injection lines in steam injection. Isolation valves are used throughout the low pressure process including ball, gate and triple-offset valves. Pressure management is carried out on all pressure vessels and lines. Control and choke valves are installed on well pads and production. Instrumentation, actuation and controls are installed throughout. In the ideal situation, suppliers and process engineers would work together in the early stages of a project.

Fate of remnant sinuses of Valsalva in patients with bicuspid and trileaflet valves undergoing aortic valve, ascending aorta, and aortic arch replacement.

Science.gov (United States)

Milewski, Rita Karianna; Habertheuer, Andreas; Bavaria, Joseph E; Siki, Mary; Szeto, Wilson Y; Krause, Eric; Korutla, Varun; Desai, Nimesh D; Vallabhajosyula, Prashanth

2017-08-01

In patients presenting with aortic valvulopathy with concomitant ascending aortic aneurysm, surgical management of the sinus of Valsalva segment remains undefined, especially for moderately dilated aortic roots. In patients with this pathology undergoing aortic valve replacement with supracoronary ascending aorta replacement, we assessed the fate of the remnant preserved sinus of Valsalva segment stratified by aortic valve morphology and pathology. From 2002 to 2015, 428 patients underwent elective aortic valve replacement with supracoronary ascending aorta replacement. Patients were stratified on the basis of valvular morphology (bicuspid aortic valve [n = 254] and tricuspid aortic valve [n = 174]), valvular pathology (bicuspid aortic valve with aortic stenosis [n = 178], bicuspid aortic valve with aortic insufficiency [n = 76], tricuspid aortic valve with aortic stenosis [n = 61], tricuspid aortic valve with aortic insufficiency [n = 113]), and preoperative sinus of Valsalva dimensions (45 mm). Kaplan-Meier analysis revealed no significant difference in freedom from reoperation in tricuspid aortic valve versus bicuspid aortic valve (P = .576). Multivariable Cox regression model performed with sinus of Valsalva dimensions at baseline and follow-up as time-varying covariates did not adversely affect survival. A repeated-measure, mixed-effects model constructed to assess longitudinal sinus of Valsalva trends revealed that the retained sinus of Valsalva dimensions remain stable over long-term follow-up (discharge to ≥10 years), irrespective of valvular morphology/pathology (bicuspid aortic valve with aortic insufficiency, tricuspid aortic valve with aortic insufficiency, tricuspid aortic valve with aortic stenosis) and preoperative sinus of Valsalva groups (45 mm). In patients with nonaneurysmal sinuses of Valsalva undergoing aortic valve replacement with supracoronary ascending aorta replacement, the sinus segment can be preserved irrespective of

Additively Manufactured Main Fuel Valve Housing

Science.gov (United States)

Eddleman, David; Richard, Jim

2015-01-01

Selective Laser Melting (SLM) was utilized to fabricate a liquid hydrogen valve housing typical of those found in rocket engines and main propulsion systems. The SLM process allowed for a valve geometry that would be difficult, if not impossible to fabricate by traditional means. Several valve bodies were built by different SLM suppliers and assembled with valve internals. The assemblies were then tested with liquid nitrogen and operated as desired. One unit was also burst tested and sectioned for materials analysis. The design, test results, and planned testing are presented herein.

Anatomic characteristics of bileaflet mitral valve prolapse--Barlow disease--in patients undergoing mitral valve repair.

Science.gov (United States)

Rostagno, Carlo; Droandi, Ginevra; Rossi, Alessandra; Bevilacqua, Sergio; Romagnoli, Stefano; Montesi, Gian Franco; Stefàno, Pier Luigi

2014-01-01

Barlow disease is a still challenging pathology for the surgeon. Aim of the present study is to report anatomic abnormalities of mitral valve in patients undergoing mitral valve repair. Between January 1st, 2007, and December 31st, 2010, 85 consecutive patients (54 men and 31 women, mean age 59 +/- 14 years--range: 28-85 years) with the features of a Barlow mitral valve disease underwent mitral repair Forty seven percent of patients were in New York Heart Association functional class III or IV. Preoperative transesophageal echocardiography was compared with anatomical findings at the moment of surgery. Transthoracic echocardiography diagnosis of Barlow disease according to the criteria described by Carpentier was confirmed at anatomical inspection. Annular calcifications were found in 28 patients while 7 patients presented single or multiple clefts. A flail posterior mitral leaflet was detected in 32 subjects, while a flail anterior leaflet in 8. Elongation of chordae tendineae was demonstrated in 45 patients and chordal rupture in 31. All patients showed at trans esophageal echocardiography the typical features of Barlow disease. Seventy-seven (90.6%) patients had severe mitral valve regurgitation, in the remaining 9.4% it was moderate to severe. Transesophageal echocardiography failed to identify clefts in 2/7 and chordal rupture in 4/31. bileaflet prolapse > 2 mm, billowing valve with excess tissue and thickened leaflets > or = 3 mm, and severe annular dilatation, are characteristics of Barlow disease, however the identification of the associated and complex abnormalities of mitral valve is necessary to obtain optimal valve repair.

Comparative evaluation of a natural gas expansion plant integrated with an IC engine and an organic Rankine cycle

International Nuclear Information System (INIS)

Kostowski, Wojciech J.; Usón, Sergio

2013-01-01

Highlights: • Comparison of natural gas expansion systems integrated with gas boiler, ICE and ORC. • Expansion systems replace the throttling process in pressure regulating stations. • 5 System performance indicators based on the 1st and 2nd law are defined. • Exergy efficiency was calculated from the fuel-product approach. • ORC system yields highest exergy efficiency 52.6% and performance ratio of 0.771. - Abstract: The aim of the paper is to propose and evaluate an innovative exergy recovery system for natural gas expansion, based on the integration of an internal combustion engine (ICE) and an organic Rankine cycle (ORC), and to compare it with other alternatives. Natural gas expansion plants are a substantial improvement to the conventional gas pressure reduction stations, based on the throttling process, since the available physical exergy of pressurized gas is converted into mechanical energy by means of an expansion machine (turbine or piston expander) instead of being lost in the throttling process. However, due to the hydrate formation problem the gas has to be pre-heated prior to the expansion, which diminishes the system performance. An efficient method for performing this pre-heating is by the proposed system that comprises an ICE and an ORC: Pre-heating of natural gas is carried out partially directly by the co-generation module, via the engine cooling cycle, and partially indirectly, by means of the engine exhaust gases, which supply heat for the ORC, while the ORC condenser is connected with the lowest stage of natural gas pre-heating. Other alternatives are the use of an ICE without ORC, the use of a boiler, and even expansion in a throttling valve. The paper evaluates the performance of the aforementioned four configurations by means of both energy and exergy analysis. Several alternative performance indicators have been defined, calculated and discussed. Sources of irreversibilities have been identified by means of exergy analysis

Method and apparatus for filling cryogenic liquid cylinders

International Nuclear Information System (INIS)

Remes, S.

1984-01-01

A method and apparatus are disclosed for filling a portable cryogenic liquid cylinder from a large stand tank. The invention employs a regulator valve to perform an automatic throttling function whereby the pressure in the liquid cylinder is maintained at a value slightly lower than the upstream pressure in the stand tank. This significantly reduces filling losses due to flashing

Cavitation noise from butterfly valves

International Nuclear Information System (INIS)

Rahmeyer, W.J.

1982-01-01

Cavitation in valves can produce levels of intense noise. It is possible to mathematically express a limit for a design level of cavitation noise in terms of the cavitation parameter sigma. Using the cavitation parameter or limit, it is then possible to calculate the flow conditions at which a design level of cavitation noise will occur. However, the intensity of cavitation increases with the upstream pressure and valve size at a constant sigma. Therefore, it is necessary to derive equations to correct or scale the cavitation limit for the effects of different upstream pressures and valve sizes. The following paper discusses and presents experimental data for the caviation noise limit as well as the cavitation limits of incipient, critical, incipient damage, and choking cavitation for butterfly valves. The main emphasis is on the design limit of caviation noise, and a noise level of 85 decibels was selected as the noise limit. Tables of data and scaling exponents are included for applying the design limits for the effects of upstream pressure and valve size. (orig.)

Plunger with simple retention valve

International Nuclear Information System (INIS)

Fekete, A.V.

1987-01-01

This patent describes a positive displacement retention valve apparatus in which the actual flow equals the theoretical maximum flow through the retention valve. The apparatus includes, in combination, a confined fluid flow conduit, a piston adapted for reciprocal movement within the fluid flow conduit between upstream and downstream limit positions, piston reciprocating means, and pressure responsive check valve means located upstream with respect to the piston in the fluid flow conduit. The pressure responsive check valve means operable to permit fluid flow therethrough in a downstream direction toward the piston, and to preclude fluid flow therethrough in an opposite direction. The piston is composed of parts which are relatively movable with respect to one another. The piston includes a simple retention valve consisting of a plug means, a cylinder having a minimum and a maximum internal cross section flow area therein and being reciprocal within the confined fluid flow conduit, and a seat on the cylinder for the plug means. The piston reciprocating means are operatively connected to the plug means

Is valve choice a significant determinant of paravalular leak post-transcatheter aortic valve implantation? A systematic review and meta-analysis.

Science.gov (United States)

O'Sullivan, Katie E; Gough, Aideen; Segurado, Ricardo; Barry, Mitchel; Sugrue, Declan; Hurley, John

2014-05-01

Paravalvular regurgitation (PVR) following transcatheter aortic valve implantation (TAVI) is associated with poor survival. The two main valve delivery systems used to date differ significantly in both structure and deployment technique. The primary objective of this study was to perform a systematic review and meta-analysis of studies identifying PVR in patients post-TAVI using Medtronic CoreValve (MCV) and Edward Sapien (ES) valves in order to identify whether a significant difference exists between valve types. The secondary objective was to identify additional factors predisposing to PVR to provide an overview of the other associated considerations. A systematic review and meta-analysis of the current literature to identify PVR rate in patients with MCV and ES valves was performed. We also sought to examine other factors predisposing to PVR. A total of 5910 patients were identified from 9 studies. PVR rates for MCV and ES were analysed. MCV was associated with a higher PVR rate of 15.75% [95% confidence interval (CI) 12.48-19.32] compared with ES 3.93% [95% CI 1.05-8.38]. We separately reviewed predisposing factors associated with PVR. A formal comparison of the MCV and ES valve leakage rates by mixed-effects meta-regression with a fixed-effect moderator variable for valve type (MCV or ES) suggested a statistically significant difference in leakage rate between the two valve types (P = 0.0002). Unfavourable anatomical and pathological factors as well as valve choice have an impact on rates of PVR. Additionally, certain anatomical features dictate valve choice. A direct comparison of all the predisposing factors at this time is not possible and will require prospective multivariate analysis. There is, however, a significant difference in the PVR rates between valves based on the published observational data available to date. The ES valve associated with a lower incidence of PVR overall; therefore, we conclude that valve choice is indeed a significant

David valve-sparing aortic root replacement: equivalent mid-term outcome for different valve types with or without connective tissue disorder.

Science.gov (United States)

Kvitting, John-Peder Escobar; Kari, Fabian A; Fischbein, Michael P; Liang, David H; Beraud, Anne-Sophie; Stephens, Elizabeth H; Mitchell, R Scott; Miller, D Craig

2013-01-01

Although implicitly accepted by many that the durability of valve-sparing aortic root replacement in patients with bicuspid aortic valve disease and connective tissue disorders will be inferior, this hypothesis has not been rigorously investigated. From 1993 to 2009, 233 patients (27% bicuspid aortic valve, 40% Marfan syndrome) underwent Tirone David valve-sparing aortic root replacement. Follow-up averaged 4.7 ± 3.3 years (1102 patient-years). Freedom from adverse outcomes was determined using log-rank calculations. Survival at 5 and 10 years was 98.7% ± 0.7% and 93.5% ± 5.1%, respectively. Freedom from reoperation (all causes) on the aortic root was 92.2% ± 3.6% at 10 years; 3 reoperations were aortic valve replacement owing to structural valve deterioration. Freedom from structural valve deterioration at 10 years was 96.1% ± 2.1%. No significant differences were found in survival (P = .805, P = .793, respectively), reoperation (P = .179, P = .973, respectively), structural valve deterioration (P = .639, P = .982, respectively), or any other functional or clinical endpoints when patients were stratified by valve type (tricuspid aortic valve vs bicuspid aortic valve) or associated connective tissue disorder. At the latest echocardiographic follow-up (95% complete), 202 patients (94.8%) had none or trace aortic regurgitation, 10 (4.7%) mild, 0 had moderate to severe, and 1 (0.5%) had severe aortic regurgitation. Freedom from greater than 2+ aortic regurgitation at 10 years was 95.3% ± 2.5%. Six patients sustained acute type B aortic dissection (freedom at 10 years, 90.4% ± 5.0%). Tirone David reimplantation valve-sparing aortic root replacement in carefully selected young patients was associated with excellent clinical and echocardiographic outcome in patients with either a tricuspid aortic valve or bicuspid aortic valve. No demonstrable adverse influence was found for Marfan syndrome or connective tissue disorder on durability, clinical outcome

49 CFR 195.260 - Valves: Location.

Science.gov (United States)

2010-10-01

... 49 Transportation 3 2010-10-01 2010-10-01 false Valves: Location. 195.260 Section 195.260... PIPELINE Construction § 195.260 Valves: Location. A valve must be installed at each of the following locations: (a) On the suction end and the discharge end of a pump station in a manner that permits isolation...

Impact of patient-prosthesis mismatch after transcatheter aortic valve-in-valve implantation in degenerated bioprostheses.

Science.gov (United States)

Seiffert, Moritz; Conradi, Lenard; Baldus, Stephan; Knap, Malgorzata; Schirmer, Johannes; Franzen, Olaf; Koschyk, Dietmar; Meinertz, Thomas; Reichenspurner, Hermann; Treede, Hendrik

2012-03-01

Transcatheter valve-in-valve implantation is evolving as an alternative to reoperative valve replacement in high-risk patients with degenerated bioprostheses. Nevertheless, hemodynamic performance is limited by the previously implanted xenograft. We report our experience with patient-prosthesis mismatch (PPM) after valve-in-valve implantation in the aortic position. Eleven patients (aged 79.3 ± 6.1 years) received transapical implantation of a balloon-expandable pericardial heart valve into a degenerated bioprosthesis (size, 23.9 ± 1.6 mm; range, 21-27 mm) in the aortic position. All patients were considered high risk for surgical valve replacement (logistic European System for Cardiac Operative Risk Evaluation, 31.8% ± 24.1%). Severe PPM was defined as an indexed effective orifice area less than 0.65 cm(2)/m(2), determined by discharge echocardiography. Severe PPM was evident in 5 patients (group 1) and absent in 6 patients (group 2). Mean transvalvular gradients decreased from 29.2 ± 15.4 mm Hg before implantation to 21.2 ± 9.7 mm Hg at discharge (group 1) and from 28.2 ± 9.0 mm Hg before implantation to 15.2 ± 6.5 mm Hg at discharge (group 2). Indexed effective orifice area increased from 0.5 ± 0.1 cm(2)/m(2) to 0.6 ± 0.1 cm(2)/m(2) and from 0.6 ± 0.3 cm(2)/m(2) to 0.8 ± 0.3 cm(2)/m(2). Aortic regurgitation decreased from grade 2.0 ± 1.1 to 0.4 ± 0.5 overall. No differences in New York Heart Association class improvement or survival during follow-up were observed. One patient required reoperation for symptomatic PPM 426 days after implantation. Valve-in-valve implantation can be performed in high-risk surgical patients to avoid reoperation. However, PPM frequently occurs, making adequate patient selection crucial. Small bioprostheses (body surface area less than 1.8 m(2). Larger prostheses seem to carry a lower risk for PPM. Although no delay in clinical improvement was seen at short-term, 1 PPM-related surgical intervention raises concern regarding

Promising results after percutaneous mitral valve repair

DEFF Research Database (Denmark)

Ihlemann, Nikolaj; Franzen, Olaf; Jørgensen, Erik

2011-01-01

Mitral valve regurgitation (MR) is the secondmost frequent valve disease in Europe. Untreated MR causes considerable morbidity and mortality. In the elderly, as many as half of these patients are denied surgery because of an estimated high surgical risk. Percutaneous mitral valve repair with the ...... with the MitraClip system resembles the Alfieristitch where a clip is used to connect the tip of the mitral valve leaflets....

Preliminary assessment of valve IST effectiveness

International Nuclear Information System (INIS)

Grove, E.; DiBiasio, A.; Carbonaro, J.

1994-01-01

A preliminary review of inservice testing effectiveness for Code Class 1,2, and 3 valves at nuclear power plants was performed. These requirements are specified by the American Society of Mechanical Engineers Boiler and Pressure Vessel Code, Section XI, and the Operations and Maintenance Standard. The Institute of Nuclear Power Operations Nuclear Plant Reliability Data System (NPRDS) database was used to provide failure reports for these components for 1988 to 1992. This time period coincides with the issuance of Generic Letter 89-04, which resulted in a more consistent application of the requirements by the licensees. For this time period, 8,593 valve failures were identified. From the review of the NPRDS database, the primary failure causes and failure modes for motor-operated valves (MOV), air-operated valves (AOV), and check valves (CV) were identified. Solenoid-operated valves were not reviewed in this study. Plant testing programs were effective in identifying approximately 60% of the CV failures, 46% of the AOV failures, and 44% of the MOV failures

Histopathological and Immunohistochemical Evaluation of Pannus Tissue in Patients with Prosthetic Valve Dysfunction.

Science.gov (United States)

Karakoyun, Süleyman; Ozan Gürsoy, Mustafa; Yesin, Mahmut; Kalçık, Macit; Astarcıoğlu, Mehmet Ali; Gündüz, Sabahattin; Emrah Oğuz, Ali; Çoban Kökten, Şermin; Nimet Karadayı, Ayşe; Tuncer, Altuğ; Köksal, Cengiz; Gökdeniz, Tayyar; Özkan, Mehmet

2016-01-01

Prosthetic valve dysfunction due to pannus formation is a rare but serious complication. Currently, limited data are available concerning the pathogenesis and immunohistochemical properties of pannus. The study aim was to investigate the morphological, histopathological and immunohistochemical characteristics of pannus formation in patients with prosthetic valve dysfunction. A total of 35 patients (10 males, 25 females; mean age 44 ± 16 years) who had undergone re-do valve surgery due to prosthetic valve obstruction was enrolled in the study. Immunohistochemical studies were aimed at evaluating the expression of alphasmooth muscle actin (α-SMA) and desmin in myofibroblasts and smooth muscle cells; epithelial membrane antigen (EMA) in epithelial cells; and CD34, Factor VIII and vascular endothelial growth factor (VEGF) in endothelial cells. Matrix metalloproteinases (MMPs) -2 and -9, and transforming growth factor-beta (TGF-β) were used to demonstrate cytokine release from macrophages, leukocytes, fibroblasts and myofibroblasts. Pannus appeared as a tough and thick tissue hyperplasia which began from outside the suture ring in the periannular region and extended to the inflow and outflow surfaces of the prosthetic valves. Histopathological analysis showed the pannus tissue to consist of chronic inflammatory cells (lymphocytes, plasma cells, macrophages and foreign body giant cells), spindle cells such as myofibroblasts, capillary blood vessels and endothelial cells laying down the lumens. Calcification was present in the pannus tissue of 19 explanted prostheses. Immunohistochemical studies revealed positive α-SMA expression in all patients, whereas 60.5% of patients were positive for desmin, 50% for EMA, 42.1% for VEGF, 39.5% for TBF-β, 42.1% for MMP-2, 86.8% for CD34, and 97.4% for Factor VIII. MMP-9 was negative in all patients. Pannus tissue appears to be formed as the result of a neointimal response in periannular regions of prosthetic valves that consist

Water hammer caused by closure of turbine safety spherical valves

Science.gov (United States)

Karadžić, U.; Bergant, A.; Vukoslavčević, P.

2010-08-01

This paper investigates water hammer effects caused by closure of spherical valves against the discharge. During the first phase of modernisation of Perućica high-head hydropower plant (HPP), Montenegro, safety spherical valves (inlet turbine valves) have been refurbished on the first two Pelton turbine units. The valve closure is controlled by the valve actuator (hydraulic servomotor). Because the torque acting on the valve body is dependent on flow conditions the valve closing time may vary significantly for different flow velocities (passive valve). For the passive valve the torques acting on the valve body should be considered in the valve model. The valve closing time results from numerical simulation. On the contrary, for the active valve the valve closing time is assumed prior to simulation. The spherical valve boundary condition is incorporated into the method of characteristics (MOC) algorithm. The staggered (diamond) grid in applying the MOC is used in this paper. The passive valve boundary condition is described by the water hammer equations, the valve equation that relates discharge to pressure head drop and the dynamic equation of the valve body motion (torque equation). The active valve boundary condition is described by the first two equations, respectively. Standard quasi-steady friction model is used for estimating friction losses in plant's tunnel and penstocks. Numerical results using both the active and the passive spherical valve models are compared with results of measurements. It has been found that the influence of flow conditions on the spherical valve closing time is minor for the cases considered. Computed and measured results agree reasonably well.

Water hammer caused by closure of turbine safety spherical valves

International Nuclear Information System (INIS)

Karadzic, U; Vukoslavcevic, P; Bergant, A

2010-01-01

This paper investigates water hammer effects caused by closure of spherical valves against the discharge. During the first phase of modernisation of Perucica high-head hydropower plant (HPP), Montenegro, safety spherical valves (inlet turbine valves) have been refurbished on the first two Pelton turbine units. The valve closure is controlled by the valve actuator (hydraulic servomotor). Because the torque acting on the valve body is dependent on flow conditions the valve closing time may vary significantly for different flow velocities (passive valve). For the passive valve the torques acting on the valve body should be considered in the valve model. The valve closing time results from numerical simulation. On the contrary, for the active valve the valve closing time is assumed prior to simulation. The spherical valve boundary condition is incorporated into the method of characteristics (MOC) algorithm. The staggered (diamond) grid in applying the MOC is used in this paper. The passive valve boundary condition is described by the water hammer equations, the valve equation that relates discharge to pressure head drop and the dynamic equation of the valve body motion (torque equation). The active valve boundary condition is described by the first two equations, respectively. Standard quasi-steady friction model is used for estimating friction losses in plant's tunnel and penstocks. Numerical results using both the active and the passive spherical valve models are compared with results of measurements. It has been found that the influence of flow conditions on the spherical valve closing time is minor for the cases considered. Computed and measured results agree reasonably well.

Water hammer caused by closure of turbine safety spherical valves

Energy Technology Data Exchange (ETDEWEB)

Karadzic, U; Vukoslavcevic, P [Faculty of Mechanical Engineering, University of Montenegro Dzordza Vasingtona nn, Podgorica, 81000 (Montenegro); Bergant, A, E-mail: uros.karadzic@ac.m [LitostrojPower d.o.o., Litostrojska 50, Ljubljana, 1000 (Slovenia)

2010-08-15

This paper investigates water hammer effects caused by closure of spherical valves against the discharge. During the first phase of modernisation of Perucica high-head hydropower plant (HPP), Montenegro, safety spherical valves (inlet turbine valves) have been refurbished on the first two Pelton turbine units. The valve closure is controlled by the valve actuator (hydraulic servomotor). Because the torque acting on the valve body is dependent on flow conditions the valve closing time may vary significantly for different flow velocities (passive valve). For the passive valve the torques acting on the valve body should be considered in the valve model. The valve closing time results from numerical simulation. On the contrary, for the active valve the valve closing time is assumed prior to simulation. The spherical valve boundary condition is incorporated into the method of characteristics (MOC) algorithm. The staggered (diamond) grid in applying the MOC is used in this paper. The passive valve boundary condition is described by the water hammer equations, the valve equation that relates discharge to pressure head drop and the dynamic equation of the valve body motion (torque equation). The active valve boundary condition is described by the first two equations, respectively. Standard quasi-steady friction model is used for estimating friction losses in plant's tunnel and penstocks. Numerical results using both the active and the passive spherical valve models are compared with results of measurements. It has been found that the influence of flow conditions on the spherical valve closing time is minor for the cases considered. Computed and measured results agree reasonably well.

How to insure quality valve remanufacture

International Nuclear Information System (INIS)

Scott, C.F.

1991-01-01

The importance of quality valve repair for the power generation industry is an obvious need for both the owner as well as the consumer. Whether valves are repaired in-line, on-site, or at a valve remanufacturing facility, the selection of a vendor is vital to meeting not only stringent quality requirements, but also to meet start-up schedules and budgets. In the past, the rule of thumb was that repair of a valve could cost approximately 50% of the cost of a new valve and still represent a significant savings to the end user. For power generation facilities, the fact that many valves are welded in not only makes repair more economical, but even vital to continuing normal operations. For those items not welded in, long lead times and higher prices for these normally exotic alloys make remanufactured valves even more attractive. However, even as these advantages of remanufacturing are obvious, some repair organizations continue to cut corners to meet profit demands. The result is suspect quality in some valves. This can lead to premature failures, possible reduced generating capacity, unscheduled outages, and even catastrophic results. Therefore, the choice of a repair organization must be made with care. As the author has said, repair is an obvious option, but the procurement should definitely involve more than just price comparisons. Evaluation must place the emphasis on quality and reliability. Several aspects should be thoroughly investigated and documented in the selection process. These include: personnel; equipment/facilities; procedures; and credentials

Aortic or Mitral Valve Replacement With the Biocor and Biocor Supra

Science.gov (United States)

2017-04-26

Aortic Valve Insufficiency; Aortic Valve Regurgitation; Aortic Valve Stenosis; Aortic Valve Incompetence; Mitral Valve Insufficiency; Mitral Valve Regurgitation; Mitral Valve Stenosis; Mitral Valve Incompetence

Compact expertise in valves. Planning software for all areas of water supply and sewage disposal; Armaturenwissen kompakt. Planungssoftware rund um die Wasser- und Abwasserwirtschaft

Energy Technology Data Exchange (ETDEWEB)

Gamper, Silke [VAG-Armaturen GmbH, Mannheim (Germany)

2009-09-15

Engineers, operators and users of water supply systems world-wide use the VAG UseCAD {sup registered} valve software programme for their daily work. The success story of this software began with its first release in the year 1994. Today, Version 6 of this valve planning software programme is available and the number of users increases year by year. The wide range of potential applications makes the universal VAG UseCAD {sup registered} planning program interesting to various groups of users. The software helps them to find the right valve for the intended application, to find suitable nominal diameters for specific flow rates and to plan the equipment to eliminate cavitation. (orig.)

A shut-off valve for flexible tubing

Science.gov (United States)

Reyburn, W. W.

1972-01-01

Design of light weight valve for flexible tubing is described. Valve is hand operated and provides positive sealing in normally closed position. Diagram is provided to show construction of valve. Principles of operation are explained.

Factors influencing left ventricular outflow tract obstruction following a mitral valve-in-valve or valve-in-ring procedure, part 1.

Science.gov (United States)

Bapat, Vinnie; Pirone, Francesco; Kapetanakis, Stam; Rajani, Ronak; Niederer, Steven

2015-10-01

To determine the factors influencing left ventricular outflow tract (LVOT) area reduction after a mitral valve-in-valve (VIV) or a valve-in-ring (VIR) procedure. Transcatheter heart valves (THVs) are increasingly used in performing a VIV or a VIR procedure in high-risk patients. Although less invasive, a potential complication is LVOT obstruction. However, the factors predisposing to LVOT obstruction are ill defined. To understand the effects of the various factors, the study was carried out in three parts: To understand the effect of VIV and VIR on reduction in LVOT area with special attention to different surgical heart valve (SHV) orientations and depth of THV implant. This was carried out in porcine and cadaver hearts. To quantify aorto-mitral-annular (AMA) angle in 20 patients with or without mitral disease and to derive a static computational model to predict LVOT obstruction. To study the effect of SHV design on LVOT obstruction after VIV. This was carried out as a bench test. LVOT area reduction was similar after VIV irrespective of orientation of the mitral SHV implantation as it pinned open the SHV leaflets. Similar effect was seen after VIR. The degree of LVOT obstruction was partly determined by AMAangle and was inversely proportional. SHV design, ring design, and depth of SPAIEN XT implantation also had effect on LVOT obstruction. A possibility of LVOT obstruction should be considered when performing a VIV and VIR procedure. Type of SHV, flexible ring, less obtuse AMA angle, and depth of SAPIEN XT implant can influence the risk. © 2015 Wiley Periodicals, Inc.

A Systematic Review of Infective Endocarditis in Patients With Bovine Jugular Vein Valves Compared With Other Valve Types.

Science.gov (United States)

Sharma, Ashutosh; Cote, Anita T; Hosking, Martin C K; Harris, Kevin C

2017-07-24

The aim of this study was to systematically evaluate the incidence of infective endocarditis (IE) in right ventricle-to-pulmonary artery conduits and valves, comparing bovine jugular vein (BJV) valves with all others. Recent evidence suggests that the incidence of IE is higher in patients with congenital heart disease who have undergone implantation of BJV valves in the pulmonary position compared with other valves. Systematic searches of published research were conducted using electronic databases (MEDLINE, Embase, and CINAHL) and citations cross-referenced current to April 2016. Included studies met the following criteria: patients had undergone right ventricle-to-pulmonary artery conduit or percutaneous pulmonary valve implantation, and investigators reported on the type of conduit or valve implanted, method of intervention (surgery or catheter based), IE incidence, and follow-up time. Fifty studies (Levels of Evidence: 2 to 4) were identified involving 7,063 patients. The median cumulative incidence of IE was higher for BJV compared with other valves (5.4% vs. 1.2%; p endocarditis with BJV valves than other types of right ventricle-to-pulmonary artery conduits. There was no difference in the incidence of endocarditis between catheter-based bovine valves and surgically implanted bovine valves, suggesting that the substrate for future infection is related to the tissue rather than the method of implantation. Copyright © 2017 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

Survival and freedom from aortic valve-related reoperation after valve-sparing aortic root replacement in 1015 patients.

Science.gov (United States)

Kari, Fabian A; Doll, Kai-Nicolas; Hemmer, Wolfgang; Liebrich, Markus; Sievers, Hans-Hinrich; Richardt, Doreen; Reichenspurner, Hermann; Detter, Christian; Siepe, Matthias; Czerny, Martin; Beyersdorf, Friedhelm

2016-04-01

The aim of this study was to characterize mortality and aortic valve replacement after valve-sparing aortic root replacement (V-SARR) in a multicentre cohort. Between 1994 and 2014, 1015 patients had V-SARR with (n = 288, 28%) or without cusp/commissure repair (n = 727, 72%) at the centres of Lübeck (n = 343, 34%), Stuttgart (n = 346, 34%), Hamburg (n = 109, 11%) and Freiburg (n = 217, 21%), Germany. Comparative survival of an age- and gender-matched general population was calculated. Log-rank tests and multiple logistic regression were used to identify risk factors. The mean follow-up was 5.2 ± 3.9 years. Cumulative follow-up comprised 2933 patient-years. Early survival was 98%. NYHA status and aneurysm size were predictive of death during mid-term follow-up (P = 0.025). Freedom from aortic valve replacement was 90% at 8 years, with the type of V-SARR (root remodelling, David II) being a risk factor (P = 0.015). Bicuspid aortic valve (P = 0.26) and initial valve function (P = 0.4) did not impact reoperation. The need of additional valve repair (cusps/commissures) was not linked to reoperation: freedom from aortic valve replacement at 8 years was 84% if cusp repair was performed versus 90% if V-SARR alone was performed (P = 0.218). Marfan syndrome had no impact on survival or on aortic valve replacement. Mid-term survival of patients after V-SARR is comparable with that of a matched general population. The regurgitant bicuspid aortic valve is a favourable substrate for V-SARR. Prophylactic surgery should be performed before symptoms or large aneurysms are present to achieve optimal mid-term outcomes. © The Author 2015. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.

Long-Term Risk for Aortic Complications After Aortic Valve Replacement in Patients With Bicuspid Aortic Valve Versus Marfan Syndrome.

Science.gov (United States)

Itagaki, Shinobu; Chikwe, Joanna P; Chiang, Yuting P; Egorova, Natalia N; Adams, David H

2015-06-09

Bicuspid aortic valves are associated with valve dysfunction, ascending aortic aneurysm and dissection. Management of the ascending aorta at the time of aortic valve replacement (AVR) in these patients is controversial and has been extrapolated from experience with Marfan syndrome, despite the absence of comparative long-term outcome data. This study sought to assess whether the natural history of thoracic aortopathy after AVR in patients with bicuspid aortic valve disease is substantially different from that seen in patients with Marfan syndrome. In this retrospective comparison, outcomes of 13,205 adults (2,079 with bicuspid aortic valves, 73 with Marfan syndrome, and 11,053 control patients with acquired aortic valve disease) who underwent primary AVR without replacement of the ascending aorta in New York State between 1995 and 2010 were compared. The median follow-up time was 6.6 years. The long-term incidence of thoracic aortic dissection was significantly higher in patients with Marfan syndrome (5.5 ± 2.7%) compared with those with bicuspid valves (0.55 ± 0.21%) and control group patients (0.41 ± 0.08%, p Marfan syndrome (10.8 ± 4.4%) compared with those with bicuspid valves (4.8 ± 0.8%) and control group patients (1.4 ± 0.2%) (p Marfan syndrome were significantly more likely to undergo thoracic aortic surgery in late follow-up (10.4 ± 4.3%) compared with those with bicuspid valves (2.5 ± 0.6%) and control group patients (0.50 ± 0.09%) (p Marfan syndrome compared with those with bicuspid aortic valves confirm that operative management of patients with bicuspid aortic valves should not be extrapolated from Marfan syndrome and support discrete treatment algorithms for these different clinical entities. Copyright © 2015 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

Porcine Tricuspid Valve Anatomy and Human Compatibility: Relevance for Preclinical Validation of Novel Valve Interventions.

Science.gov (United States)

Waziri, Farhad; Lyager Nielsen, Sten; Michael Hasenkam, John

2016-09-01

Tricuspid regurgitation may be a precursor for heart failure, reduced functional capacity, and poor survival. A human compatible experimental model is required to understand the pathophysiology of the tricuspid valve disease as a basis for validating novel tricuspid valve interventions before clinical use. The study aim was to evaluate and compare the tricuspid valve anatomy of porcine and human hearts. The anatomy of the tricuspid valve and the surrounding structures that affect the valve during a cardiac cycle were examined in detail in 100 fresh and 19 formalin-fixed porcine hearts obtained from Danish Landrace pigs (body weight 80 kg). All valvular dimensions were compared with human data acquired from literature sources. No difference was seen in the tricuspid annulus circumference between porcine and human hearts (13.0 ± 1.2 cm versus 13.5 ± 1.5 cm; p = NS), or in valve area (5.7 ± 1.6 cm2 versus 5.6 ± 1.0 cm2; p = NS). The majority of chordae types exhibited a larger chordal length and thickness in human hearts compared to porcine hearts. In both species, the anterior papillary muscle (PM) was larger than other PMs in the right ventricle, but muscle length varied greatly (range: 5.2-40.3 mm) and was significantly different in pigs and in humans (12.2 ± 3.2 mm versus 19.2 mm; p human hearts.

Infective endocarditis following percutaneous pulmonary valve replacement

DEFF Research Database (Denmark)

Cheung, Gary; Vejlstrup, Niels; Ihlemann, Nikolaj

2013-01-01

Infective endocarditis (IE) following percutaneous pulmonary valve replacement (PPVR) with the Melody valve is rarely reported. Furthermore, there are challenges in this diagnosis; especially echocardiographic evidence of vegetation within the prosthesis may be difficult.......Infective endocarditis (IE) following percutaneous pulmonary valve replacement (PPVR) with the Melody valve is rarely reported. Furthermore, there are challenges in this diagnosis; especially echocardiographic evidence of vegetation within the prosthesis may be difficult....

Assessment of structural valve deterioration of transcatheter aortic bioprosthetic balloon-expandable valves using the new European consensus definition.

Science.gov (United States)

Eltchaninoff, Hélène; Durand, Eric; Avinée, Guillaume; Tron, Christophe; Litzler, Pierre-Yves; Bauer, Fabrice; Dacher, Jean-Nicolas; Werhlin, Camille; Bouhzam, Najime; Bettinger, Nicolas; Candolfi, Pascal; Cribier, Alain

2018-03-30

Durability of transcatheter aortic bioprosthetic valves remains a major issue. Standardised definitions of deterioration and failure of bioprosthetic valves have recently been proposed. The aim of this study was to assess structural transcatheter valve deterioration (SVD) and bioprosthetic valve failure (BVF) using these new definitions. All TAVI patients implanted up to September 2012 with a minimal theoretical five-year follow-up were included. Systematic clinical and echocardiographic follow-up was performed annually. New standardised definitions were used to assess durability of transcatheter aortic bioprosthetic valves. From 2002 to 2012, 378 patients were included. Mean age and logistic EuroSCORE were 83.3±6.8 years and 22.8±13.1%. Thirty-day mortality was 13.2%. Nine patients had SVD including two severe forms and two patients had definite late BVF. The incidence of SVD and BVF at eight years was 3.2% (95% CI: 1.45-6.11) and 0.58% (95% CI: 0.15-2.75), respectively. Even though limited by the poor survival of the very high-risk/compassionate early population, our data do not demonstrate any alarm concerning transcatheter aortic valve durability. Careful prospective assessment in younger and lower-risk patients and comparison with surgical bioprosthetic valves are required for further assessment of the long-term durability of transcatheter valves.

NRC Information No. 90-21: Potential failure of motor-operated butterfly valves to operate because valve seat friction was underestimated

International Nuclear Information System (INIS)

Rossi, C.E.

1992-01-01

In October 1988, at Catawba Nuclear Station Unit 1, a motor-operated butterfly valve in the service water system failed to open under high differential pressure conditions. The licensee concluded that the valve manufacturer, BIF/General Signal Corporation, had underestimated the degree to which the material used in the valve seat would harden with age (the responsibility for these valves has been transferred to Paul-Munroe Enertech). This underestimation of the age hardening had led the manufacturer to assume valve seat friction forces that were less than the actual friction forces in the installed valve. To overcome the larger-than-anticipated friction forces, the licensee's engineering staff recommended the open torque switch for 56 butterfly valves be reset to the maximum allowable value. The systems in which these valves are located include the component cooling water system, service water system, and various ventilation systems. By July 26, 1989, the torque switch adjustments were completed at Catawba Units 1 and 2. After reviewing the final settings, the licensee's engineering staff determined that the actuators for three butterfly valves in the component cooling water system might not be able to overcome the friction forces resulting from maximum seat hardening. On December 13, 1989, the licensee determined that the failure of these BIF/General Signal motor-operated valves (MOVs) could cause a loss of cooling water to residual heat removal system heat exchangers. To resolve the concern regarding the operability of these BIF/General Signal valves, a torque switch bypass was installed on two of the actuators to allow full motor capability during opening

Dysfunction of an On-X Heart Valve by Pannus.

Science.gov (United States)

Abad, Cipriano; Urso, Stefano; Gomez, Elsa; De la Vega, Maria

2016-09-01

A 68-year-old woman with a history of previous double-valve replacement with On-X mechanical heart valves presented with clinical, echocardiographic and cardiac catheterization signs of obstruction of the On-X tricuspid heart valve prosthesis. The patient was successfully reoperated, but at surgery the valve was seen to be invaded by an abnormal overgrowth of pannus that blocked one of the leaflets. A small amount of non-obstructive fresh thrombus was also observed. The valve was successfully replaced with a biological heart valve prosthesis. The patient was discharged home, and is doing well four months after the operation, when echocardiography demonstrated normal function in the tricuspid valve. The present case represents the first ever report of pannus formation and subsequent dysfunction in an On-X heart valve, and also the first case of tricuspid valve malfunction and obstruction using this type of heart valve substitute.

Transfemoral Aortic Valve Implantation with the New Edwards Sapien 3 Valve for Treatment of Severe Aortic Stenosis-Impact of Valve Size in a Single Center Experience.

Directory of Open Access Journals (Sweden)

Jochen Wöhrle

Full Text Available The third generation Edwards Sapien 3 (Edwards Lifesciences Inc., Irvine, California system was optimized to reduce residual aortic regurgitation and vascular complications.235 patients with severe symptomatic aortic stenosis were prospectively enrolled. Transcatheter aortic valve implantations (TAVI were performed without general anesthesia by transfemoral approach. Patients were followed for 30 days. Patients received 23mm (N = 77, 26mm (N = 91 or 29mm (N = 67 valve based on pre-procedural 256 multislice computer tomography. Mean oversizing did not differ between the 3 valves. There was no residual moderate or severe aortic regurgitation. Rate of mild aortic regurgitation and regurgitation index did not differ between groups. There was no switch to general anesthesia or conversion to surgery. Rate of major vascular complication was 3.0% with no difference between valve and delivery sheath sizes. Within 30 days rates of all cause mortality (2.6% and stroke (2.1% were low.In patients with severe aortic stenosis transfemoral TAVI with the Edwards Sapien 3 valve without general anesthesia was associated with a high rate of device success, no moderate or severe residual aortic regurgitation, low rates of major vascular complication, mortality and stroke within 30 days with no difference between the 3 valve sizes.ClinicalTrials.gov NCT02162069.

The use of transcatheter aortic valve replacement vs surgical aortic valve replacement for the treatment of aortic stenosis

Directory of Open Access Journals (Sweden)

Jensen HA

2015-08-01

Full Text Available Hanna A Jensen, Lillian L Tsai, Vinod H Thourani Division of Cardiothoracic Surgery, Joseph B Whitehead Department of Surgery, Structural Heart and Valve Center, Emory University School of Medicine, Atlanta, GA, USA Abstract: Severe aortic stenosis (AS is associated with considerable morbidity and mortality and is increasing in prevalence as the global population increases. Since AS primarily affects the elderly, many of these patients have comorbidities that make them poor candidates for the gold standard treatment for AS, surgical aortic valve replacement. Transcatheter aortic valve replacement has emerged as a novel technology for the management of AS in higher risk patients over the past decade. Randomized trials have established the safety and efficacy of transcatheter aortic valve replacement, and the medical community has rallied to identify the patients who are most suitable for this transformative treatment. This review focuses on outlining the key procedural differences, describing the unique challenges of both operations, and finally assessing and comparing outcomes both on a general level and in challenging patient subgroups. Keywords: aortic valve replacement, transcatheter aortic valve replacement, surgical aortic valve replacement 

Surgery for rheumatic mitral valve disease in sub-saharan African countries: why valve repair is still the best surgical option.

Science.gov (United States)

Mvondo, Charles Mve; Pugliese, Marta; Giamberti, Alessandro; Chelo, David; Kuate, Liliane Mfeukeu; Boombhi, Jerome; Dailor, Ellen Marie

2016-01-01

Rheumatic valve disease, a consequence of acute rheumatic fever, remains endemic in developing countries in the sub-Saharan region where it is the leading cause of heart failure and cardiovascular death, involving predominantly a young population. The involvement of the mitral valve is pathognomonic and mitral surgery has become the lone therapeutic option for the majority of these patients. However, controversies exist on the choice between valve repair or prosthetic valve replacement. Although the advantages of mitral valve repair over prosthetic valve replacement in degenerative mitral disease are well established, this has not been the case for rheumatic lesions, where the use of prosthetic valves, specifically mechanical devices, even in poorly compliant populations remains very common. These patients deserve more accurate evaluation in the choice of the surgical strategy which strongly impacts the post-operative outcomes. This report discusses the factors supporting mitral repair surgery in rheumatic disease, according to the patients' characteristics and the effectiveness of the current repair techniques compared to prosthetic valve replacement in developing countries.

Magnon Valve Effect between Two Magnetic Insulators

Science.gov (United States)

Wu, H.; Huang, L.; Fang, C.; Yang, B. S.; Wan, C. H.; Yu, G. Q.; Feng, J. F.; Wei, H. X.; Han, X. F.

2018-03-01

The key physics of the spin valve involves spin-polarized conduction electrons propagating between two magnetic layers such that the device conductance is controlled by the relative magnetization orientation of two magnetic layers. Here, we report the effect of a magnon valve which is made of two ferromagnetic insulators (YIG) separated by a nonmagnetic spacer layer (Au). When a thermal gradient is applied perpendicular to the layers, the inverse spin Hall voltage output detected by a Pt bar placed on top of the magnon valve depends on the relative orientation of the magnetization of two YIG layers, indicating the magnon current induced by the spin Seebeck effect at one layer affects the magnon current in the other layer separated by Au. We interpret the magnon valve effect by the angular momentum conversion and propagation between magnons in two YIG layers and conduction electrons in the Au layer. The temperature dependence of the magnon valve ratio shows approximately a power law, supporting the above magnon-electron spin conversion mechanism. This work opens a new class of valve structures beyond the conventional spin valves.

Flowfield Analysis of a Pneumatic Solenoid Valve

Directory of Open Access Journals (Sweden)

Sheam-Chyun Lin

2018-07-01

Full Text Available Pneumatic solenoid valve has been widely used in the vehicle control systems for meeting the rapid-reaction demand triggered by the dynamic conditions encountered during the driving course of vehicle. For ensuring the safety of human being, the reliable and effective solenoid valve is in great demand to shorten the reaction time and thus becomes the topic of this research. This numerical study chooses a commercial 3/2-way solenoid valve as the reference valve for analysing its performance. At first, CFD software Fluent is adopted to simulate the flow field associated with the valve configuration. Then, the comprehensive flow visualization is implemented to identify the locations of adverse flow patterns. Accordingly, it is found that a high-pressure region exists in the zone between the nozzle exit and the top of iron core. Thereafter, the nozzle diameter and the distance between nozzle and spool are identified as the important design parameters for improving the pressure response characteristics of valve. In conclusion, this work establishes a rigorous and systematic CFD scheme to evaluate the performance of pneumatic solenoid valve.

Leakage characterization of a piloted power operated relief valve

International Nuclear Information System (INIS)

Ezekoye, L.I.; Hess, M.D.

1995-01-01

In Westinghouse Pressurized Water Reactors (PWRs), power operated relief valves (PORVs) are used to provide overpressure protection of the Pressurizer. The valves are fail closed globe valves which means that power is required to open the valves and, on loss of power, the valves close. There are two ways to operate the PORVs. The more common way is to directly couple the disc to an actuator via a disc-stem assembly. The type of design is not the object of this paper. The other and less common way of operating a PORV is by piloting the main valve such that the opening or closing of a pilot valve opens and closes the main valve. This is the design of interest. In most plants, the PORVs are installed with a water loop seal while in some plants no water loop seals are used. It is generally accepted that loop seal installation minimizes valve seat leakage. In non-loop seal installation, the valve seat is exposed to steam which increases the potential for seat leakage. This paper describes the results of some tests performed with nitrogen and steam to characterize the leakage potential of a pilot operated PORV. The test results were compared with seat leakage tests of check valves to provide insight on the leakage testing of pilot operated valves and check valves. The paper also compares the test data with leakage estimates using the ASME/ANSI OM Code guidance on valve leakage

Classification of heart valve condition using acoustic measurements

Energy Technology Data Exchange (ETDEWEB)

Clark, G. [Lawrence Livermore National Lab., CA (United States)

1994-11-15

Prosthetic heart valves and the many great strides in valve design have been responsible for extending the life spans of many people with serious heart conditions. Even though the prosthetic valves are extremely reliable, they are eventually susceptible to long-term fatigue and structural failure effects expected from mechanical devices operating over long periods of time. The purpose of our work is to classify the condition of in vivo Bjork-Shiley Convexo-Concave (BSCC) heart valves by processing acoustic measurements of heart valve sounds. The structural failures of interest for Bscc valves is called single leg separation (SLS). SLS can occur if the outlet strut cracks and separates from the main structure of the valve. We measure acoustic opening and closing sounds (waveforms) using high sensitivity contact microphones on the patient`s thorax. For our analysis, we focus our processing and classification efforts on the opening sounds because they yield direct information about outlet strut condition with minimal distortion caused by energy radiated from the valve disc.

Heart Valve Surgery Recovery and Follow Up

Science.gov (United States)

... Guide: Understanding Your Heart Valve Problem | Spanish Symptom Tracker | Spanish Pre-surgery Checklist | Spanish What Is Heart ... Heart Valves • Heart Valve Problems and Causes • Risks, Signs and Symptoms • Accurate Diagnosis • Treatment Options • Recovery and ...

Bjork-Shiley convexoconcave valves: Susceptibility artifacts at brain MR imaging and mechanical valve fractures

NARCIS (Netherlands)

van Gorp, Maarten J.; van der Graaf, Yolanda; de Mol, Bas A. J. M.; Bakker, Chris J. G.; Witkamp, Theo D.; Ramos, Lino M. P.; Mali, Willem P. T. M.

2004-01-01

PURPOSE: To assess the relationship between heart valve history and susceptibility artifacts at magnetic resonance (MR) imaging of the brain in patients with Bjork-Shiley convexoconcave (BSCC) valves. MATERIALS AND METHODS: MR images of the brain were obtained in 58 patients with prosthetic heart

A 29-Year-Old Harken Disk Mitral Valve

Science.gov (United States)

Hsi, David H.; Ryan, Gerald F.; Taft, Janice; Arnone, Thomas J.

2003-01-01

An 81-year-old woman was evaluated for prosthetic mitral valve function. She had received a Harken disk mitral valve 29 years earlier due to severe mitral valve disease. This particular valve prosthesis is known for premature disk edge wear and erosion. The patient's 2-dimensional Doppler echocardiogram showed the distinctive appearance of a disk mitral valve prosthesis. Color Doppler in diastole showed a unique crown appearance, with initial flow acceleration around the disk followed by convergence to laminar flow in the left ventricle. Cineradiographic imaging revealed normal valve function and minimal disk erosion. We believe this to be the longest reported follow-up of a surviving patient with a rare Harken disk valve. We present images with unique echocardiographic and cineangiographic features. (Tex Heart Inst J 2003;30:319–21) PMID:14677746

Characterizing nanoscale topography of the aortic heart valve basement membrane for tissue engineering heart valve scaffold design.

Science.gov (United States)

Brody, Sarah; Anilkumar, Thapasimuthu; Liliensiek, Sara; Last, Julie A; Murphy, Christopher J; Pandit, Abhay

2006-02-01

A fully effective prosthetic heart valve has not yet been developed. A successful tissue-engineered valve prosthetic must contain a scaffold that fully supports valve endothelial cell function. Recently, topographic features of scaffolds have been shown to influence the behavior of a variety of cell types and should be considered in rational scaffold design and fabrication. The basement membrane of the aortic valve endothelium provides important parameters for tissue engineering scaffold design. This study presents a quantitative characterization of the topographic features of the native aortic valve endothelial basement membrane; topographical features were measured, and quantitative data were generated using scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), and light microscopy. Optimal conditions for basement membrane isolation were established. Histological, immunohistochemical, and TEM analyses following decellularization confirmed basement membrane integrity. SEM and AFM photomicrographs of isolated basement membrane were captured and quantitatively analyzed. The basement membrane of the aortic valve has a rich, felt-like, 3-D nanoscale topography, consisting of pores, fibers, and elevations. All features measured were in the sub-100 nm range. No statistical difference was found between the fibrosal and ventricular surfaces of the cusp. These data provide a rational starting point for the design of extracellular scaffolds with nanoscale topographic features that mimic those found in the native aortic heart valve basement membrane.

Control rod driving hydraulic device

International Nuclear Information System (INIS)

Sugano, Hiroshi.

1993-01-01

In a control rod driving hydraulic device for an improved BWR type reactor, a bypass pipeline is disposed being branched from a scram pipeline, and a control orifice and a throttle valve are interposed to the bypass pipeline for restricting pressure. Upon occurrence of scram, about 1/2 of water quantity flowing from an accumulator of a hydraulic control unit to the lower surface of a piston of control rod drives by way of a scram pipeline is controlled by the restricting orifice and the throttle valve, by which the water is discharged to a pump suction pipeline or other pipelines by way of the bypass pipeline. With such procedures, a function capable of simultaneously conducting scram for two control rod drives can be attained by one hydraulic control unit. Further, an excessive peak pressure generated by a water hammer phenomenon in the scram pipeline or the control rod drives upon occurrence of scram can be reduced. Deformation and failure due to the excessive peak pressure can be prevented, as well as vibrations and degradation of performance of relevant portions can be prevented. (N.H.)

Reactor containment purge and vent valve performance experiments

International Nuclear Information System (INIS)

Hunter, J.A.; Steele, R.; Watkins, J.C.

1985-01-01

Three nuclear-designed butterfly valves typical of those used in domestic nuclear power plant containment purge and vent applications were tested. For a comparison of responses, two eight-inch nominal pipe size valves with differing internal design were tested. For extrapolation insights, a 24-inch nominal pipe size valve was also tested. The valve experiments were performed with various piping configurations and valve disc orientations to the flow, to simulate various installation options in field application. As a standard for comparing the effects of the installation options, testing was also performed in a standard ANSI test section. Test cycles were performed at inlet pressures of 5 to 60 psig, while monitoring numerous test parameters, such as the valve disc position, valve shaft torque, mass flow rate, and the pressure and temperature at multiple locations throughout the test section. An experimental data base was developed to assist in the evaluation of the current analytical methods and to determine the influence of inlet pressure, inlet duct geometry, and valve orientation to the flow media on valve torque requirements, along with any resulting limitations to the extrapolation methods. 2 refs., 15 figs

Potential problems will drillstring safety valves

Energy Technology Data Exchange (ETDEWEB)

NONE

1996-06-01

In the paper titled ``New generation drill string safety valves,`` presented at the IADC Well Control Conference for Europe, Aberdeen, May 22--24, 1996, documented limitations of presently available drillstring safety valves commonly used as kelly valves and stabbing valves were presented, and industry efforts to develop solutions to these problems were described. Authors of the paper are B.A. Tarr and R.A. Sukup (Mobil E and P Technology Center, Dallas), Dr. R. Luy (ITE, Clausthal, Germany), G. Rabby (Hi-Kalibre, Edmonton, Alberta) and J. Mertsch (ITAG, Celle, Germany). In 1995, the Task Group developed a draft of a new spec, and a DSSV testing program was initiated as a joint industry project, with the Gas Research Institute (GRI) as the major sponsor. Two manufacturers, Hi-Kalibre and ITAG, agreed to build new valves for the testing program. Hi-Kalibre, Edmonton, Alberta, supplied an already-commercial twin floating ball valve for November 1995 testing. This product is being used by Tesco in its portable top drive system. ITAG of Germany supplied a radically improved DSSV design, which was tested in December, and was to be retested in May following modifications.

A correlation for safety valve blowdown and ring settings

International Nuclear Information System (INIS)

Singh, A.; Shak, D.

1982-01-01

The blowdown of a spring loaded safety valve is defined as the difference between the pressure at which the valve opens and the pressure at which the valve fully closes under certain fluid flow conditions. Generally, the blowdown is expressed in terms of percentage of the opening pressure. An extensive series of tests carried out in the EPRI/PWR Utilities Valve Test Program has shown that the blowdown of safety valves can in general be strongly dependent upon the valve geometry and other parameters such as ring adjustments, spring stiffness, backpressure etc. In the present study, correlations have been developed using the EPRI safety valve test data to predict the expected blowdown as a function of adjustment ring settings for geometrically similar valves under steam discharge conditions. The correlation is validated against two different size Dresser valves

High-risk Trans-Catheter Aortic Valve Replacement in a Failed Freestyle Valve with Low Coronary Height: A Case Report

OpenAIRE

Karimi, Ashkan; Pourafshar, Negiin; Dibu, George; Beaver, Thomas M.; Bavry, Anthony A.

2017-01-01

A 55-year-old male with a history of two prior cardiac surgeries presented with decompensated heart failure due to severe bioprosthetic aortic valve insufficiency. A third operation was viewed prohibitively high risk and valve-in-valve trans-catheter aortic valve replacement was considered. There were however several high-risk features and technically challenging aspects including low coronary ostia height, poor visualization of the aortic sinuses, and difficulty in identification of the copl...

Stent fracture, valve dysfunction, and right ventricular outflow tract reintervention after transcatheter pulmonary valve implantation: patient-related and procedural risk factors in the US Melody Valve Trial.

Science.gov (United States)

McElhinney, Doff B; Cheatham, John P; Jones, Thomas K; Lock, James E; Vincent, Julie A; Zahn, Evan M; Hellenbrand, William E

2011-12-01

Among patients undergoing transcatheter pulmonary valve (TPV) replacement with the Melody valve, risk factors for Melody stent fracture (MSF) and right ventricular outflow tract (RVOT) reintervention have not been well defined. From January 2007 to January 2010, 150 patients (median age, 19 years) underwent TPV implantation in the Melody valve Investigational Device Exemption trial. Existing conduit stents from a prior catheterization were present in 37 patients (25%, fractured in 12); 1 or more new prestents were placed at the TPV implant catheterization in 51 patients. During follow-up (median, 30 months), MSF was diagnosed in 39 patients. Freedom from a diagnosis of MSF was 77±4% at 14 months (after the 1-year evaluation window) and 60±9% at 39 months (3-year window). On multivariable analysis, implant within an existing stent, new prestent, or bioprosthetic valve (combined variable) was associated with longer freedom from MSF (Pbioprosthetic valve was associated with lower risk of MSF and reintervention.

250 kV aim for hvdc valves

Energy Technology Data Exchange (ETDEWEB)

1966-06-01

Development now being carried out by ASEA is aimed at increasing the normal operating voltage for a mercury arc valve to 250 kV dc. The maximum direct voltage per valve group, with one valve in each arm of the bridge, is 125 kV for equipment already in operation in New Zealand, Japan, and Konti Scan. Valves for 130 kV and 133 kV operation are under construction for the Vancouver and the Pacific Intertie 1 links.

Investigation of a rotary valving system with variable valve timing for internal combustion engines

Science.gov (United States)

Cross, Paul C.; Hansen, Craig N.

1994-11-01

The objective of the program was to provide a functional demonstration of the Hansen Rotary Valving System with Variable Valve Timing (HRVS/VVT), capable of throttleless inlet charge control, as an alternative to conventional poppet-valves for use in spark ignited internal combustion engines. The goal of this new technology is to secure benefits in fuel economy, broadened torque band, vibration reduction, and overhaul accessibility. Additionally, use of the variable valve timing capability to vary the effective compression ratio is expected to improve multifuel tolerance and efficiency. Efforts directed at the design of HRVS components proved to be far more extensive than had been anticipated, ultimately requiring that proof-trial design/development work be performed. Although both time and funds were exhausted before optical or ion-probe types of in-cylinder investigation could be undertaken, a great deal of laboratory data was acquired during the course of the design/development work. This laboratory data is the basis for the information presented in this final report.

Bentall Procedure Using Cryopreserved Valved Aortic Homografts

Science.gov (United States)

Christenson, Jan T.; Sierra, Jorge; Trindade, Pedro T.; Didier, Dominique; Kalangos, Afksendiyos

2004-01-01

The Bentall procedure is the standard operation for patients who have lesions of the ascending aorta associated with aortic valve disease. In many cases, however, mechanical prosthetic conduits are not suitable. There are few reports in the English-language medical literature concerning the mid- to long-term outcome of Bentall operations with cryopreserved homografts. Therefore, we reviewed our experience with this procedure and valved homografts. From January 1997 through December 2002, 21 patients underwent a Bentall operation with cryopreserved homografts at our institution. There were 14 males and 7 females; the mean age was 36 ± 21 years (range, 15–74 years). Eleven patients had undergone previous aortic valve surgery. All patients had aortic dilatation or aneurysms involving the ascending aorta. Indications for surgery included aortic valve stenosis or insufficiency, and aortic valve endocarditis (native valve or prosthetic). One patient had Takayasu's arteritis and 3 had Marfan syndrome. There was 1 hospital death (due to sepsis), but no other major postoperative complications. The mean hospital stay was 14 ± 7 days. Follow-up echocardiographic and computed tomographic scans were performed yearly. The mean follow-up was 34 months (6–72 months). Follow-up imaging revealed no calcifications or degenerative processes related to the homograft. Four patients had minimal valve regurgitation. Two patients died during follow-up. The 3-year actuarial survival rate was 85.7%. Our data suggest that the Bentall procedure with a valved homograft conduit is a safe procedure with excellent mid- to long-term results, comparable to results reported with aortic valve replacement with a homograft. PMID:15745290

Transcatheter Mitral Valve Devices - Functional Mechanical Designs.

Science.gov (United States)

Kliger, Chad

2014-03-01

Mitral regurgitation is a complex disorder involving a multitude of components of the mitral apparatus. With the desire for less invasive treatment approaches, transcatheter mitral valve therapies (TMVT) are directed at these components and available at varying stages of development. Therapeutic advancements and the potential to combine technologies may further improve their efficacy and safety. Transcatheter mitral valve replacement, while preserving the mitral apparatus, may emerge as an alternative or even a more suitable treatment option. In addition, early data on transcatheter mitral valve-in-valve and valve-in-ring implantation are encouraging and this approach may be an alternative to reoperation in the high-risk patient. This review details the expanding functional mechanical designs of current active TMVT.

The influence of Marfans and bicuspid valves on outcomes following aortic valve reimplantation.

Science.gov (United States)

Martín, Carlos E; García Montero, Carlos; Serrano, Santiago-Fiz; González, Ana; Mingo, Susana; Moñivas, Vanessa; Centeno, Jorge; Forteza, Alberto

2017-10-01

We analyzed our early and midterm results with aortic valve reimplantation surgery to determine the influence of Marfan syndrome and bicuspid valves on outcomes with this technique. Between March 2004 and December 2015, 267 patients underwent aortic valve reimplantation operations. The mean diameter of the sinuses of Valsalva was 50 ± 3 mm and moderate/severe aortic regurgitation was present in 34.4% of these patients. A bicuspid aortic valve was present in 21% and 40% had Marfan syndrome. Overall 30-day mortality was 0.37% (1/267). Mean follow-up was 59.7 ± 38.7 months. Overall survival at 1, 3, and 5 years was 98 ± 8%, 98 ± 1%, and 94 ± 2%, respectively. Freedom from reoperation and aortic regurgitation >II was 99 ± 5%, 98 ± 8%, 96.7 ± 8%, and 99 ± 6%, 98 ± 1%, 98 ± 1%, respectively at 1, 3, and 5 years follow-up, with no differences between Marfan and bicuspid aortic valve groups. (p = 0.94 and p = 0.96, respectively). No endocarditis or thromboembolic complications were documented, and 93.6% of the patients did not receive any anticoagulation therapy. The reimplantation technique for aortic root aneurysms is associated with excellent clinical and functional outcomes at short and mid-term follow-up. © 2017 Wiley Periodicals, Inc.

Volume-constrained optimization of magnetorheological and electrorheological valves and dampers

Science.gov (United States)

Rosenfeld, Nicholas C.; Wereley, Norman M.

2004-12-01

This paper presents a case study of magnetorheological (MR) and electrorheological (ER) valve design within a constrained cylindrical volume. The primary purpose of this study is to establish general design guidelines for volume-constrained MR valves. Additionally, this study compares the performance of volume-constrained MR valves against similarly constrained ER valves. Starting from basic design guidelines for an MR valve, a method for constructing candidate volume-constrained valve geometries is presented. A magnetic FEM program is then used to evaluate the magnetic properties of the candidate valves. An optimized MR valve is chosen by evaluating non-dimensional parameters describing the candidate valves' damping performance. A derivation of the non-dimensional damping coefficient for valves with both active and passive volumes is presented to allow comparison of valves with differing proportions of active and passive volumes. The performance of the optimized MR valve is then compared to that of a geometrically similar ER valve using both analytical and numerical techniques. An analytical equation relating the damping performances of geometrically similar MR and ER valves in as a function of fluid yield stresses and relative active fluid volume, and numerical calculations are provided to calculate each valve's damping performance and to validate the analytical calculations.

Valve for gas centrifuges

Science.gov (United States)

Hahs, Charles A.; Burbage, Charles H.

1984-01-01

The invention is a pneumatically operated valve assembly for simultaneously (1) closing gas-transfer lines connected to a gas centrifuge or the like and (2) establishing a recycle path between two of the lines so closed. The valve assembly is especially designed to be compact, fast-acting, reliable, and comparatively inexpensive. It provides large reductions in capital costs for gas-centrifuge cascades.

Coanda effect in valves

Directory of Open Access Journals (Sweden)

Uruba Václav

2017-01-01

Full Text Available Coanda effect takes place in flow within valves diffuser for certain conditions. The valve plug in half-closed position forms wall-jet, which could be stable or instable, depending on geometry and other conditions. This phenomenon was subject of experimental study using time-resolved PIV technique. For the acquired data analysis the special spatio-temporal methods have been used.

Oil pipeline valve automation for spill reduction

Energy Technology Data Exchange (ETDEWEB)

Mohitpour, Mo; Trefanenko, Bill [Enbridge Technology Inc, Calgary (Canada); Tolmasquim, Sueli Tiomno; Kossatz, Helmut [TRANSPETRO - PETROBRAS Transporte S.A., Rio de Janeiro, RJ (Brazil)

2003-07-01

Liquid pipeline codes generally stipulate placement of block valves along liquid transmission pipelines such as on each side of major river crossings where environmental hazards could cause or are foreseen to potentially cause serious consequences. Codes, however, do not stipulate any requirement for block valve spacing for low vapour pressure petroleum transportation, nor for remote pipeline valve operations to reduce spills. A review of pipeline codes for valve requirement and spill limitation in high consequence areas is thus presented along with a criteria for an acceptable spill volume that could be caused by pipeline leak/full rupture. A technique for deciding economically and technically effective pipeline block valve automation for remote operation to reduce oil spilled and control of hazards is also provided. In this review, industry practice is highlighted and application of the criteria for maximum permissible oil spill and the technique for deciding valve automation thus developed, as applied to ORSUB pipeline is presented. ORSUB is one of the three initially selected pipelines that have been studied. These pipelines represent about 14% of the total length of petroleum transmission lines operated by PETROBRAS Transporte S.A. (TRANSPETRO) in Brazil. Based on the implementation of valve motorization on these three pipeline, motorization of block valves for remote operation on the remaining pipelines is intended, depending on the success of these implementations, on historical records of failure and appropriate ranking. (author)

Steel-fabricated butterfly valves for condenser circulating water system

International Nuclear Information System (INIS)

Kawase, Hiroshi; Yasuoka, Masahiro; Nanao, Teruaki.

1979-01-01

The steel-fabricated butterfly valves, which are large in general, and gave rubber linings inside to prevent the corrosion due to sea Water, are utilized for the condenser circulating water systems of thermal and nuclear power plants. Cast iron butterfly valves, having been used hitherto, have some technical irrationalities, such as corrosion prevention, the techniques for manufacturing large castings, severe thermal transient operation. On the contrary, the steel plate-fabricated butterfly valves have the following advantages; much superior characteristics in strength, rigidity and shock resistance, the streamline shape of valve plates, the narrow width between two flanges, superior execution of works for rubber lining, the perfect sealed structure, safety to vibration, light weight and easy maintenance. The structural design and the main specifications for the steel plate butterfly valves with the nominal bore from 1350 mm to 3500 mm are presented. Concerning the design criteria, the torque of operating butterfly valves and the strength of valve bodies, valve plates and valve stems are explained. The performance tests utilizing the mock-up valve were carried out for the measurements of stress distribution, the deformation of valve body, the endurance and the operating torque. In the welding standards for steel plate butterfly valves, three kinds of welded parts are classified, and the inspection method for each part is stipulated. The vibration of the valves induced by flow vortexes and cavitation is explained. (Nakai, Y.)

Outlet strut fracture of Björk-Shiley convexo-concave valves: can valve-manufacturing characteristics explain the risk?