Valve Assembly Research Articles

Progress in developing a living human tissue-engineered tri-leaflet heart valve assembled from tissue produced by the self-assembly approach

The aortic heart valve is constantly subjected to pulsatile flow and pressure gradients which, associated with cardiovascular risk factors and abnormal hemodynamics (i.e. altered wall shear stress), can cause stenosis and calcification of the leaflets and result in valve malfunction and impaired circulation. Available options for valve replacement include homograft, allogenic or xenogenic graft as well as the implantation of a mechanical valve. A tissue-engineered heart valve containing living autologous cells would represent an alternative option, particularly for pediatric patients, but still needs to be developed. The present study was designed to demonstrate the feasibility of using a living tissue sheet produced by the self-assembly method, to replace the bovine pericardium currently used for the reconstruction of a stented human heart valve. In this study, human fibroblasts were cultured in the presence of sodium ascorbate to produce tissue sheets. These sheets were superimposed to create a thick construct. Tissue pieces were cut from these constructs and assembled together on a stent, based on techniques used for commercially available replacement valves. Histology and transmission electron microscopy analysis showed that the fibroblasts were embedded in a dense extracellular matrix produced in vitro. The mechanical properties measured were consistent with the fact that the engineered tissue was resistant and could be cut, sutured and assembled on a wire frame typically used in bioprosthetic valve assembly. After a culture period in vitro, the construct was cohesive and did not disrupt or disassemble. The tissue engineered heart valve was stimulated in a pulsatile flow bioreactor and was able to sustain multiple duty cycles. This prototype of a tissue-engineered heart valve containing cells embedded in their own extracellular matrix and sewn on a wire frame has the potential to be strong enough to support physiological stress. The next step will be to test this valve extensively in a bioreactor and at a later date, in a large animal model in order to assess in vivo patency of the graft.

Influence of Operation Conditions on Mean Time Between Failures of Valve Assemblies in Gas Distribution Networks

We have examined the requirements of valve assemblies used in gas distribution networks, reviewed the materials used for making packing surfaces of ball cocks, analyzed the basic causes of failures, conducted experimental studies, and determined the contribution of each wearing process (wearing due to friction of packing surfaces of shutoff unit, fretting, and attack of gas-abrasive stream) that causes failure of packing surfaces of valve assemblies. Based on the studies conducted on determination of wear resistance of materials and the analysis made of the contribution of each factor, we have built a mathematical model to determine the mean time between failures of valve assemblies for various operation conditions.

Simulation Analysis of Boring Finishing Process for a Thermal Power Unit's Valve Body

Control valve is the key element for a thermal power unit. As the core component of the valve assembly, the machining quality of valve bodys mating part is an important factor to restrict the performance of valve, so during the machining process, the demands for dimensional accuracy and surface quality of mating surface are quite high. Firstly, set the cutting tool, cutting parameters and other initial conditions according to enterprises actual requirements of body machining. The Deform 3D which is metal cutting finite element software was used to simulate the boring finishing process of mating surface of the valve body, can effectively analyze the changing rule of cutting force and cutting temperature with time. Then, the single factor analysis method was used to analyze the deformation of boring cutter due to cutting force, temperature and abrasion under the condition of different cutting parameters, which influence the quality and precision of valve bodys machining surface. The analysis results obtained in this paper will provide reference for the choice of cutting parameters in the process of actual valve body finish machining.

Characterization of an aerodynamic lens for transmitting particles greater than 1 micrometer in diameter into the Aerodyne aerosol mass spectrometer

Abstract. We have designed and characterized a new inlet and aerodynamic lens for the Aerodyne aerosol mass spectrometer (AMS) that transmits particles between 80 nm and more than 3 μm in vacuum aerodynamic diameter. The design of the inlet and lens was optimized with computational fluid dynamics (CFD) modeling of particle trajectories. Major changes include a redesigned critical orifice holder and valve assembly, addition of a relaxation chamber behind the critical orifice, and a higher lens operating pressure. The transmission efficiency of the new inlet and lens was characterized experimentally with size-selected particles. Experimental measurements are in good agreement with the calculated transmission efficiency.

Wading Through the Stream of Commerce: When Can Foreign Manufacturers Expect to be Subject to Specific Jurisdiction in United States Courts?

THE QUESTION of whether a court may exercise personal jurisdiction over foreign product manufacturers on the basis of introducing goods into the of has produced much litigation and confusion since that phrase was introduced in World-Wide Volkswagen Corp. v. Woodson. (1) Recently, after two decades of relative silence, the United States Supreme Court attempted to clarify the stream-of-commerce doctrine in J. McIntyre Machinery, Ltd. v. Nicastro (2) and Goodyear Dunlop Tires Operations, S.A. v. Brown. (3) Unfortunately, although Goodyear articulated some helpful limits on general jurisdiction, neither decision clarified the stream-of-commerce theory of specific jurisdiction. As a result, foreign manufacturers continue to face uncertainty about when they can expect to be haled into a particular United States court under that theory. This article discusses the origins of the stream-of-commerce doctrine and its development through the years, including the Supreme Court's most recent decisions on the issue--McIntyre and Goodyear. Despite the confusion left intact after McIntyre and Goodyear, as a practical matter, courts have tended to focus on three broad factors in deciding whether to assert specific jurisdiction over foreign manufacturers. Those factors are: a manufacturer's awareness of or control over downstream distribution, the volume of product that enters the market, and the manufacturer's with the United States overall as compared to the forum where suit is brought. This article discusses a number of representative post-McIntyre cases that consider these factors in their analyses of stream-of-commerce jurisdiction and provides a list of specific facts that may inform a court's analysis of these three factors in a given case. I. The Origins and Development of the Stream-of-Commerce Doctrine A. Origins of, and Confusion Over, the Doctrine In addition to any restrictions that a state's particular long-arm statute may provide, federal constitutional due process requires that the defendant have certain minimum with [the forum state] such that the maintenance of the suit does not offend 'traditional notions of fair play and substantial justice.' (4) Minimum contacts requires the defendant to have purposefully avail[ed] itself of the privilege of conducting activities within the forum State. (5) Purposeful availment may arise when a manufacturer introduces goods into the of commerce, a phrase introduced by the Supreme Court in World-Wide Volkswagen. In that case, the Court said, in dicta, that [t]he forum State does not exceed its powers under the Due Process Clause if it asserts personal jurisdiction over a [foreign] corporation that delivers its products into the stream of commerce with the expectation that they will be purchased by consumers in the forum State. (6) Seizing upon this language, some lower courts asserted that a manufacturer can be subject to jurisdiction simply by introducing goods into the stream of commerce. (7) The Supreme Court again addressed the stream-of-commerce theory in Asahi Metal Industry Co., Ltd. v. Superior Court of California. (8) Asahi was a product liability action arising out of a motorcycle accident. The rider of the motorcycle asserted that he was injured and that his passenger was killed because the motorcycle's rear tire exploded. The rider brought suit in California state court against both the Taiwanese manufacturer of the tire tube and the Japanese manufacturer of the tube's valve assembly. The Taiwanese manufacturer filed a crossclaim seeking indemnification from the Japanese manufacturer. The injured rider eventually settled his own claims, leaving only the crossclaim by the Taiwanese manufacturer against the Japanese manufacturer, and the Japanese manufacturer moved to dismiss on the basis of a lack of personal jurisdiction. Ultimately, the Supreme Court held, in a part of an opinion authored by Justice O'Connor and joined by seven other Justices, that jurisdiction over the Japanese manufacturer would be unreasonable and unfair. …

Disposable miniature check valve design suitable for scalable manufacturing

We present a passive, miniature check valve which can be manufactured using standard techniques ideal for low-cost, disposable systems used in medical devices and other applications. The body of the valve consists of a hollow cylindrical core, closed at one end, with a side port and a cylindrical elastomeric sleeve placed over the core body, covering the side port. The pressure required for initial opening of the valve, referred to as cracking pressure, can be adjusted, and depends predominantly on the valve core outer diameter, the sleeve inner diameter, the sleeve wall thickness, and the sleeve material's modulus of elasticity. These parameters can be controlled to tight tolerances, while the tolerances on other features can be relaxed, which simplifies valve manufacturing and assembly. Valve embodiments produced from different materials, and with varying critical dimensions, exhibited distinct and reproducible cracking pressures in the range of 2–20 PSI. The cracking pressure did not vary significantly as a function of flow rate. No back flow leakage was encountered up to 30 PSI, the pressure limit of the sensor used in this experiment. Most of the valves tested had small internal volumes of 3–4μL. The internal volume can be further reduced by selecting a core of smaller inner diameter. In contrast to lithography-based microvalves that generally must be manufactured in situ within the fluidic device, the herein presented valve can be manufactured independently of, and can be readily integrated into fluidic systems manufactured via a wide selection of fabrication methods.

Control for the Lift of the Inlet Valve - Electromagnetic Drive Assembly with the Effect of Friction

It has been analyzed the assembly of electromagnetic drive - inlet valve operating in camless valvetrain. The valve made of TiAl alloy has mated with its guide made of phosphor bronze. The scheme of electromagnetic valve drive has been shown in the article. The head aim of the motion control for such valve has been to provide small values of the valve velocity near the valve seat position. The aim of present analysis is to study the course of friction force between valve stem and its guide against time during use of control algorithm presented in the article. Curses of generated electrodynamical force against displacement of coil - valve assembly has been computed using FEM method and presented in the article. The courses of valve lift against time for different conditions have been presented in the article.

In vivo dialysis setup with a loop injection valve facilitates retrodialysis studies

IntroductionRetrodialysis, as used in neuropharmacological research, is a technique for in vivo delivery of neuroactive agents with concurrent monitoring of their effects on cellular activity with a separation between certain degree of spatial and temporal resolution. Typically, this is accomplished either by the use of a liquid-switch requiring multiple pumps, or by exchange of flow tubing requiring stopping and restarting dialysis. In the present study, we describe the use of a medium pressure injection valve for retrodialysis that overcomes these problems. MethodsThe valve was configured with a loop to deliver 20μL of solution, and artificial CSF flow from the pump to the probe was established via this device. The application of this setup was evaluated in urethane anesthetized adult male C57BL/6J mice prepared with a CMA 11 probe implanted in the ventral hippocampus. By switching between the load and inject positions, the loop was filled with escitalopram solution (0.3μM) and delivered at a rate of 1μL/min at the probe for retrodialysis. Escitalopram (2mg/kg BW) was administered subcutaneously for microdialysis studies. During these treatments, dialysate fractions were collected for the determination of serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA). ResultsIrrespective of route of escitalopram administration, the pattern of dialysate 5-HT, and 5-HIAA response was comparable to that reported by other investigators. Accordingly, the in-line valve assembly did not compromise retrodialysis or microdialysis sampling. The manipulations to carry out retrodialysis using the valve setup are easy and simple. DiscussionAn in-line injection valve is a promising adaptation for retrodialysis studies and can be incorporated as a standard part of in vivo dialysis instrumentation.

Performance Analysis of an Integrated Micro Cryogenic Cooler and Miniature Compressor for Cooling to 200 K

Joule-Thomson (J-T) based micro cryogenic coolers (MCCs) are attractive because they can provide the cryogenic temperatures needed for small electronic devices while having a low cost and small volumetric footprint. A compressor is a major part of a cryogenic system, but so far J-T based MCCs have not used miniature or microscale compressors. This work demonstrates a J-T based MCC coupled with a miniature compressor for cooling to 200 K, with precooling of 273 K, using a custom hydrocarbon mixture as refrigerant. The compressor is formed by coupling a miniature piston oscillator built for stirling coolers with a micromachined check valve assembly. The MCC is formed by glass fibers within a capillary forming a counter flow heat exchanger, and a silicon and glass chip forming a J-T valve. Minimum temperatures of 166 K have been observed in transient, and stable temperatures of 200 ±1 K have been observed for >1 h. Some insight is given into the unstable performance in terms of intermittent liquid accumulation. The coefficient of performance is analyzed for the system, and it is found that most of the inefficiencies arise at the compressor.

Design of Thyristor Valve Assembly in on-Load Automatic Capacity Regulating Distribution Transformer

The working principle of on-load automatic capacity regulating distribution transformer is elaborated in this study, a layout scheme with anti-parallel thyristor valve assembly as capacity regulating switch is designed. The thyristor valve assembly is selected. The respective character in the system of electromagnetism trigger and online monitoring as well as photoelectricity trigger and online monitoring is described. With the comparison, it takes the system of electromagnetism trigger and online monitoring at last.

Design of High Speed Solenoid Actuator for Hydraulic Servo Valve Operation

Modern electric controlled valves are demanded that its solenoid actuator should be smaller size, lighter weight, lower consumption power, and higher response time. For achieving these purposes, the major design factors of solenoid actuator such as magnetic flux density, coil turn numbers, plunger size, bobbin dimension, and etc. are must be optimized. In this study, for optimal design of high speed solenoid actuator for hydraulic servo valve operation, we draw up governing equations which are composed by combination of electromagnetic theories and empirical knowledge, and deduct the values of major design factors by use of them. For more increase the operating speed, voice coil are used as main armature in manufacturing of prototype actuator. And, we have proven the propriety of the governing equations and speed increasing method by experiments using the hydraulic valve assembly adopted the prototype of solenoid actuator.

Dynamic Performance of a Three-Wheeled Vehicle Steering System, Part 1: Steering System Incorporating Directional Control Valve

During taxing, the aircraft can be treated as a three wheeled vehicle. This work deals with the dynamic behavior of this three-wheeled vehicle during the steering mode. Conventionally the hydraulic power steering systems incorporate either hydraulic or electrohydraulic servo-systems. Nevertheless, Part 1 of this paper deals with the dynamic behavior of a steering system incorporating three directional control valves of poppet type in one housing. A nonlinear mathematical model of the directional control valve assembly was developed and used to simulate the valves dynamic behavior. The validity of the simulation program was evaluated in the steady state by comparing simulation results with results of experimental work conducted on the studied valves. The construction of the mechanical parts is explained and the kinematics of the steering system was analyzed and presented. The transient response of the steering system incorporating the directional control valve assembly was calculated, presented and discussed.

Bond Graph Modeling of a Two-Stage Pressure Relief Valve

This study examined the use of bond graphs for the modeling and simulation of a fluid power system component. A new method is presented for creating the bond graph model, based upon a previously developed mathematical model. A nonlinear dynamic bond graph model for a two-stage pressure relief valve has been developed in this paper. Bond graph submodels were constructed considering each element of the studied valve assembly. The overall bond graph model of the valve was developed by combining these submodels using junction structures. Causality was then assigned in order to obtain a computational model, which could be simulated. The simulation results of the causal bond graph model were compared with those of a mathematical model, which had been also developed in this paper based on the same assumptions. The results were found to correlate very well both in the shape of the curves, magnitude, and response times. The causal bond graph model was verified experimentally in the dynamic mode of operation. As a result of comparison, bond graphs can quickly and accurately model the dynamics in a fluid power control system component. During the simulation study, it was found that nonlinearity occur due to three factors: changes in pressure, which cause nonlinear velocity changes of the flow rate; changes in the throttling area of the valve restriction, which usually changes nonlinearly; and changes in the discharge coefficient of the throttling area of the valve restriction, which does not remain constant.

A Real-Time Thermal Test Platform for Underwater Complex Structures and Heat Transfer Analysis

In order to conduct an effective and reasonable heat transfer analysis, a real-time thermal test platform was established, which consists of two flow loops, the heating system, the data acquisition system, the automatic data processing software and the relative piping system. Based on this platform, a typical T-type deadleg and a gate valve assembly are adopted to investigate their heat transfer characteristics. The experiment data are compared with the numerical calculation with great good agreements. For further application, this real-time thermal test platform could be used for cool down analysis and thermal insulation assessment. Ultimately, promotional values for similar and even much larger scale complex underwater structures could be found in this study.

The new build to print design of the ITER Torus Cryopump

The common design of the cryopumps for pumping the divertor and the cryostat has been completed at ITER following more than 10 years of development including prototyping and a number of design studies. This final design, which will be validated by building a Pre-Production Cryopump, achieves a number of simplifications and is expected to solve issues identified in previous concepts.The paper will present the build to print manufacturing design of the cryopump according to European Standards. The fabrication and qualification methods will be discussed and a summary of the main manufacturing methods will be given. The design of the valve assembly and its integration in the cryopump with the valve shaft double bellows will be described in detail.

Collision Contact Characteristics for Reciprocating Pump Using FEA and Experiments

The previous research on the pump valve is mostly focused on theory and simulation, but how much precision of these results can be obtained is rarely of concern. A new experimental approach for accurately measuring the reciprocating pump valve motion parameters has been presented. An FEA model to describe the pump valve's collision contact statealso been established. Combining the measured valve's velocity and displacement data, the collision contact characteristics in valve assembly during pump operation have been systematically analyzed by ANSYS/LS-DYNA. The von Mises stress in valve disc and its seat changed by the variables such as valve closing speed, mass, diameter, and taper angle in the collision contact process are quantitatively determined, as well as the relationship between valve's collision contact condition and pump service life. Results show that the experiment and simulation approach can truly and accurately reflect the pump valve's collision process, which provides a scientific basis for the further analysis of pump valve movement and damage mechanism and then improves the reciprocating pump design.

Finite Element Analysis of a Mechanical Heart Valve in Assembly

The Bileaflet Mechanical Heart Valve (BMHV) has been the most successful replacement mechanical heart valve, and is currently the most commonly implanted mechanical valve. Although the BMHV is an improvement over previous mechanical heart valves, there are still serious associated complications with its use that must be eliminated. After the completion of the processing and surface modification, heart valve ring and heart valve leaflets constitute a single whole with mechanical method to achieve its function process. In order to ensure that the heart valve is stable and reliable in service, it is particularly important to improve the assembly quality. The theoretical analysis and simulation used of ANSYS Workbench software for the behavior of the heart valve assembly have been done, the experimental results were verified by testing apparatus, which is a helpful tool used to simulate the new structure of the heart valve assembly, and play a certain significance to improve the accuracy of the assembly.

반도체 약액용 자동제어 플라스틱 밸브의 내부 유동해석

Diaphragm type noncontact automatic control valve is a valve for controling acidic PR(Photo Resist) liquid used in the semiconductor process. PR is photosensitive liquid that changes phases depending on light transmittance. PR is very toxic and expensive; the purpose of this paper is to address methods that prevent loss due to leaks. The design of noncontact precise automatic control valve is expected to play an important role in controlling fluid flow, therefore influencing energy conservation and environmental improvement. In this paper, diaphragm type automatic control valve's part design, assembly and simulation are introduced. Also, through the analysis of fluid flow the valve's internal velocity, pressure, and turbulent intensity are interpreted. This paper proposes to contribute to the improvement of the valve's performance.

The design and development of a stented tissue mitral and aortic heart valve replacement for human implantation.

A study was conducted into the development of a mitral and aortic heart valve replacement that caters for patients having suffered valve damage due to stenosis or rheumatic fever. The appeal of the valve is that it is constituted from a solid frame housing pericardial tissue leaflets, and allows the patient freedom from post-operative blood-thinning medication. The valve is designed to appeal to patients in developing areas of the world, as it features a clip-in mechanism to secure the valve assembly into the sewing ring, which is stitched in independently of the frame and leaflets. Re-operative valve replacement would then be made possible when the pericardial leaflets began to calcify. Novel aspects of the design added value to the science of heart valve replacements, through the use of sintered chrome cobalt in the valve components, the insights gained into mechanical testing of pericardium, and the patient benefits offered by the complete design. Further work is planned to fatigue test the assembly, undergo animal trials and make the valve available for commercial use.

Computer Aided Design of Valve Train of Cylinder

Valve train has important impact on engine’s performance and useful life. With the development of engine technology, the failure about valve train get attention gradually. Valve spring of engine is the important components in the valve assembly. In order to ensure valve and cam work reliably in poor condition, the dynamic failure analysis on them have great theoretical and engineering applied significance. So the dynamic performance and reliability of the valve train should also be concerned. The new software is a high-performance language for technical computing. It integrates computation, visualization, and programming in an easy-to-use environment where problems and solutions are expressed in familiar mathematical notation.