Virtual Valve Research Articles

Shell fluctuating asymmetry in the sea-dwelling benthic bivalve Mytilus galloprovincialis (Lamarck, 1819) as morphological markers to detect environmental chemical contamination.

Investigations on asymmetries showed that deviations from perfect bilateral symmetry are interpreted as environmental changes inducing developmental instability. Since morphological abnormalities increase with pollution, deformations may be considered indicators of the organism exposition to pollution. Therefore, the onset of asymmetry in otherwise normally symmetrical traits has been used as a measure of some stresses as well. In this context, we studied how marine pollution affects the valve morphological alterations in the mussel Mytilus galloprovincialis. We used 180 specimens (30 per site) from the aquaculture area of Goro (River Po delta, northern Adriatic Sea), translocated, and released within 50 × 50 × 50 cm cages in five sites: two disturbed and one undisturbed near Naples (eastern Tyrrhenian Sea), and one disturbed and one undisturbed near Siracusa (western Ionian Sea). Disturbed sites were stressed by heavy industrialization and heavy tankers traffic of crude and refined oil, and were defined basing on sediment contamination. In particular, by the cone-beam computed tomography we obtained 3D virtual valve surfaces to be analyzed by the geometric morphometric techniques. Specifically, we focused the levels of the shell shape fluctuating asymmetry in relation to the degrees of marine pollution in different sites of the Tyrrhenian Sea. The Mahalanobis distances (interpreted as proxy of the individual shape asymmetry deviation from the mean asymmetry) significantly regressed with the sediment contamination gradient. Indeed, although the left-right differences were normally distributed in each studied site, the individual asymmetry scores (IAS) significantly varied amongst the investigated sites. IAS showed higher values in disturbed areas than those of undisturbed ones in both Tyrrhenian and Ionian Sea. Our results are consistent with past studies on molluscans and other taxa, demonstrating some detrimental effects of chemicals on organisms, although the investigated morphological marker did not discriminate the real disturbance source. Our findings indicate that the mussels act as a prognostic tool for sea pollution levels driving detrimental effects on benthic community.

On-chip Virtual Vortex Gear

We observed an interesting phenomenon of coupled vortices in a microfluidic channel with different driving pressure. We call this phenomenon “Virtual Vortex Gear”, as the vortices transmitting like a set of gear. The channel has an elbow and a circular chamber outside the bend point. In addition to the phenomenon, we can also control the flow into the chamber by adjusting the driving pressure and we name this feature “Virtual Valve”. Microbeads were used as tracers in the experiments. The relation between the vortices and driving pressure is discussed. With simulation on COMSOL, we evaluate Virtual Valve and determine the proper size and shape for the design.

Fatigue model of a disc valve system used in shock absorbers

The aim of the paper is to formulate and validate a fatigue damage model applicable to disc spring valve systems used in automotive and railway hydraulic shock absorbers. The valve consists of a stack of thin disc springs of varying diameters which are designed to provide a controlled annular flow through a valve system. A disc spring stack is subjected to fatigue damage therefore it has to be accurately designed and validated to provide the required fatigue damage performance and minimise failure risk of shock absorber. The fatigue model developed in this work facilitates a virtual valve system pre-selection process to reduce the required testing capacity, i.e., the number of long-term and expensive fatigue tests performed on servo-hydraulic testing machines. The model accuracy was evaluated using the experimental high-cycle fatigue tests which were conducted on the high-frequency servo-hydraulic load frame machine.

Pseudo 1-D Micro/Nanofluidic Device for Exact Electrokinetic Responses.

Conventionally, a 1-D micro/nanofluidic device, whose nanochannel bridged two microchannels, was widely chosen in the fundamental electrokinetic studies; however, the configuration had intrinsic limitations of the time-consuming and labor intensive tasks of filling and flushing the microchannel due to the high fluidic resistance of the nanochannel bridge. In this work, a pseudo 1-D micro/nanofluidic device incorporating air valves at each microchannel was proposed for mitigating these limitations. High Laplace pressure formed at liquid/air interface inside the microchannels played as a virtual valve only when the electrokinetic operations were conducted. The identical electrokinetic behaviors of the propagation of ion concentration polarization layer and current-voltage responses were obtained in comparison with the conventional 1-D micro/nanofluidic device by both experiments and numerical simulations. Therefore, the suggested pseudo 1-D micro/nanofluidic device owned not only experimental conveniences but also exact electrokinetic responses.

Using 3D virtual surfaces to investigate molluscan shell shape

Noninvasive methods in shell shape variation may help to understand evolution, ecology, stress and role of molluscan in aquatic ecosystems. Imaging analysis is a suitable diagnostic tool in morphological studies to (1) evaluate the health status of investigated animals, and (2) monitor sea coastal habitats. We introduce the feasibility of the cone-beam computed tomography as an optimal technique for 3D surface scanning to obtain virtual valve surfaces of Mytilus galloprovincialis , and analyze them exploiting the geometric morphometric facilities. Statistical output revealed morphological difference between mussels coming from different extensive rearing systems highlighting how the entire valve surface contributed to discriminate between groups when we compared 2- and 3D analyses. Many factors drive the morphological differences observed in the valve shape variation between the two sites, such as geographical genetic differentiation, natural environmental effects and culture conditions. The simplicity of the proposed methodology avoids damage and handling of individuals, makes this approach useful for morphological data collection, and helps to detect detrimental agents for sea ecosystems by using molluscans.

Reliability-Aware Synthesis With Dynamic Device Mapping and Fluid Routing for Flow-Based Microfluidic Biochips

In flow-based biochips, peristaltic pumps consisting of valves are essential to generate circulation flow in a mixer. When a peristaltic pump is activated, the related valves for peristalsis are required to be actuated for many times. However, the roles of valves in traditional chips are fixed, and therefore the valves for peristalsis can wear out much faster than the valves for guiding fluid transportation. This could lead to a reduced lifetime of the chip, because the whole chip function can be affected when just a few or even only a single valve wears out. In this paper, we propose a valve-centered architecture with virtual valves, based on which we introduce a valve-role-changing concept to balance the valve actuations. By switching a valve into different roles, microfluidic components such as mixers, storages, and flow channels can be formed dynamically during the assay process, which enables us to balance the utilization of valves, and synthesize designs that support various kinds of operations. Compared with our preliminary work, we further decrease the largest number of valve actuation as well as the number of valves by the revised dynamic device mapping and fluid path routing. For dynamic device mapping, we introduce a virtual-boundary concept to generate devices at better places while connections between devices are still guaranteed. For fluid path routing, we accurately model valve actuation resulting from our valve-actuation-aware routing, and revise the results by rip-up and reroute. In addition to performance, we improve the reliability of our method by assuring fluid paths from devices to chip boundaries. Experiments show that the new method can be eight times better than the traditional method, and outperforms our preliminary work for large cases even with fewer valves.

Abstract 18319: Virtual Mitral Valve Repair for Improved Pre-surgical Planning: Quantitative Evaluation of Neochordoplasty versus Leaflet Resection

Background: Neochordoplasty and/or leaflet resection are reliable and reproducible mitral valve (MV) repair techniques for the treatment of chordal rupture with severe mitral regurgitation (MR). We developed a novel computational evaluation strategy to determine the biomechanical and physiologic characteristics of MV dynamics prior to and following potential MV repair techniques to optimize surgical planning for neochordoplasty or leaflet resection. Methods: Virtual MV models from patients with P2 chordal rupture and severe MR were created using 3D echocardiographic data (N=5). Virtual neochordoplasty was designed by adding six neochordae between the papillary muscles and the P2 scallop. Virtual resection was performed by removing a pre-defined quadrangular shaped leaflet portion in the P2 scallop and merging the excised leaflet edges. Computational simulations of MV function (pre- and post-repair) were performed using dynamic finite element methods. Coaptation lengths and leaflet stress distributions were evaluated. Results: The MVs with P2 chordal rupture demonstrated severe P2 prolapse, leaflet malcoaptation, and large stress concentrations. Both repair techniques markedly reduced posterior leaflet prolapse and restored sufficient leaflet coaptation. Virtual neochordoplasty showed larger coaptation lengths (A2-P2) compared to virtual resection. Excessive stress concentrations in the P2 scallop disappeared and peak stress values decreased by up to 85% following both repair techniques. Conclusion: We have quantitatively evaluated patient-specific MV function before and after potential MV repair using a novel virtual MV repair protocol. Both virtual neochordoplasty and leaflet resection techniques decreased posterior leaflet prolapse, lessened stress concentration, and restored leaflet coaptation. This virtual simulation strategy has the potential for improved pre-surgical planning to optimize post-repair MV function.

Composition modulated InAsSb superlattice induced by non-incorporating Bismuth

We report a new method for synthesizing a composition superlattice with molecular beam epitaxy. A repeated structure of InAs(1−x)Sb(x)/InAs(1−y)Sb(y) was induced by periodic cycling of a non-incorporating Bi-flux, while keeping the In-, As- and Sb-fluxes constant. The Bi acts as a virtual chemical valve. High-resolution X-ray diffraction demonstrated a modulation ratio of x/y=1:1.3. Composition broadening could not be detected within the experimental resolution. The Bi, despite not incorporating, also does not remain on the growing surface after the incoming Bi-flux is terminated.

Abstract 12891: Mitral Valve Analysis Adding a Virtual Semi-Transparent Annulus Plane for Improved Visualization of Prolapsing Segments

Introduction: Three-dimensional echocardiography has improved the preoperative evaluation of mitral valve disease. Though, better tools to quantify the amount of prolapsing tissue is warranted. A novel 3D holographic display (Setred AS, Oslo, Norway) offer a 3-dimensional echocardiographic presentation without the need for stereo glasses. We have developed a semi-transparent annulus plane presentation that may better quantitate the prolapsing tissue. Hypothesis: We assessed the hypothesis that it is feasible to create a semi-automatic, semi-transparent annulus plane visualized on the holographic display, demonstrating the prolapsed segment that crosses the virtual mitral valve plane. Methods: Eight patients with degenerative mitral valve disease were analysed. Three-dimensional transthoracic echocardiography was obtained from an apical view and data was converted to the holographic display for further analysis. Findings were compared with visual inspection during surgery. A semi-automated tool was used to detect the annulus; placement of annulus points was done by clicking out points at small rotation intervals around a rotation center point while rotating around the long axis. After a full rotation, the plane was triangulated using a delaunay triangulation process and the annulus plane was visualized as a semi transparent blue surface. The dataset could then be shown from surgeons view in order to see where the valve crosses the visualized valve plane. Results: A total of 48 segments were analysed. We were able to obtain an annulus plane in all and by adding the annulus mitral valve plane, the prolapsing segments could be reproduced in all cases. Figure 1 shows representative recordings (surgeons view) demonstrating a P2 prolapse in the upper panel and a large A2 prolapse in the lower panel. Conclusion: In conclusion, the presentation of a semi-transparent annulus plane was feasible and the findings correlated well with that observed during surgery.

Three-Dimensional Ultrasound-Derived Physical Mitral Valve Modeling

Advances in mitral valve repair and adoption have been partly attributed to improvements in echocardiographic imaging technology. To educate and guide repair surgery further, we have developed a methodology for fast production of physical models of the valve using novel three-dimensional (3D) echocardiographic imaging software in combination with stereolithographic printing. Quantitative virtual mitral valve shape models were developed from 3D transesophageal echocardiographic images using software based on semiautomated image segmentation and continuous medial representation algorithms. These quantitative virtual shape models were then used as input to a commercially available stereolithographic printer to generate a physical model of the each valve at end systole and end diastole. Physical models of normal and diseased valves (ischemic mitral regurgitation and myxomatous degeneration) were constructed. There was good correspondence between the virtual shape models and physical models. It was feasible to create a physical model of mitral valve geometry under normal, ischemic, and myxomatous valve conditions using 3D printing of 3D echocardiographic data. Printed valves have the potential to guide surgical therapy for mitral valve disease.

Measurement of Mitral Leaflet and Annular Geometry and Stress After Repair of Posterior Leaflet Prolapse: Virtual Repair Using a Patient-Specific Finite Element Simulation

Recurrent mitral regurgitation after mitral valve (MV) repair for degenerative disease occurs at a rate of 2.6% per year and reoperation rate progressively reaches 20% at 19.5 years. We believe that MV repair durability is related to initial postoperative leaflet and annular geometry with subsequent leaflet remodeling due to stress. We tested the hypothesis that MV leaflet and annular stress is increased after MV repair. Magnetic resonance imaging was performed before and intraoperative three-dimensional (3D) transesophageal echocardiography was performed before and after repair of posterior leaflet prolapse in a single patient. The repair consisted of triangular resection and annuloplasty band placement. Images of the heart were manually co-registered. The left ventricle and MV were contoured, surfaced, and a 3D finite element (FE) model was created. Elements of the posterior leaflet region were removed to model leaflet resection and virtual sutures were used to repair the leaflet defect and attach the annuloplasty ring. The principal findings of the current study are the following: (1) FE simulation of MV repair is able to accurately predict changes in MV geometry including changes in annular dimensions and leaflet coaptation; (2) average posterior leaflet stress is increased; and (3) average anterior leaflet and annular stress are reduced after triangular resection and mitral annuloplasty. We successfully conducted virtual mitral valve prolapse repair using FE modeling methods. Future studies will examine the effects of leaflet resection type as well as annuloplasty ring size and shape.

Computed Tomographic Imaging of Transcatheter Aortic Valve Replacement for Prediction and Prevention of Procedural Complications

Senile calcific aortic stenosis (AS) is the most common acquired valvular heart disease with an increasing prevalence attributable to an aging population. Survival is poor in patients with severe or critical AS, chiefly after the onset of symptomology that primarily includes angina, dyspnea, or syncope. On the onset of symptoms, mortality occurs at very high rates during the ensuing 2 to 3 years.1 Until recently, surgical aortic valve replacement represented the sole therapy that definitive reduced mortality and morbidity in patients with severe symptomatic AS, with medical therapy generally ineffective of these patients. Given the advanced age commonly associated with severe AS, a high proportion of these patients are denied surgical intervention because of multiple comorbidities and excessively high surgical risk.2 Recently, transcatheter aortic valve replacement (TAVR) has emerged as a novel disruptive technology that serves an alternative therapy to surgical AVR and has been shown to be an effective therapy in nonoperable and high-risk patients with severe symptomatic AS.3,4 TAVR was first described in humans by Cribier et al in 20025 by a transvenous approach delivered in an antegrade fashion. This technique requires a transseptal puncture and passage of the aortic stent valve across the mitral valve to the aortic position. Subsequently, array of alternative transvascular approaches have arisen, including transfemoral, transaortic, trans-subclavian, and aortic methods. Of these, the retrograde transarterial approach through the femoral artery, developed by Webb et al,6 has been the commonly used approach, with >60 000 such procedures performed worldwide to date. To date, the global experience with TAVR as documented in both single and multicenter registries as well as through multicenter trials have shown good clinical outcomes with improvement in hemodynamic and clinical status, establishing TAVR to be a feasible alternative therapy to traditional surgical aortic valve …

대유량 솔레노이드 밸브 개발에 관한 연구

Port size 80mm or above large-flow type solenoid valves are extensively used in dust collector and power plants. These multi-stage solenoid valve have few problem. first, multi-solenoid valves are almost depend on imports and there are weak in the brine environment and the low energy efficiency. Because these problem, increased the necessity of research on the development of large flow and high pressure type solenoid valves. In this study, describe the design method of multi-stage solenoid test bench and confirm the influence valve performance on several parameter such as diaphragm orifice diameter. At first, each part has modeled by AMESim simulation tool and combining them. This AMESim virtual multi-stage solenoid valve found influence valve performance on the valve parameter. Finally developed the multi-stage solenoid valve and verified that performance on experimental result.

Use of a virtual wall valve in polydimethylsiloxane microfluidic devices for bioanalytical applications.

A simple method for micromanipulation of liquids and∕or small groups of cells is presented in this study. Microfabricated sieving structures composed of PDMS (polydimethylsiloxane) were used to segregate aqueous solutions. This microfluidic valving scheme was an application of Cassie-Baxter wetting and was termed "virtual walls" as a nonsolid barrier exists at an air∕water interface. The manipulation of the virtual-air-wall valve was accomplished by controlling the strength of surface-tension and hydrostatic-pressure forces. Virtual walls with a range of feature sizes were designed and characterized by monitoring air and water displacement in response to hydrostatic pressure. Thresholds for the virtual-air-wall valves to be turned on or off were quantified. The walls could also be formed or dissipated by the focused microbeam of a pulsed laser. As an illustration of the virtual wall utility, a series of microfluidic applications were demonstrated. First, the capability of virtual walls to temporarily segregate liquids was integrated into a device utilized to establish a chemical gradient. In a second application, the arraying of nonadherent cells within individual aqueous cavities created by the virtual walls was demonstrated. Individual cells were also released from the cavities on demand using a focused microbeam. The virtual walls were simple and easy-to-fabricate without the requirement for surface treatment or precision alignment, and should find usage in bioanalytical applications.

Use of a virtual wall valve in polydimethylsiloxane microfluidic devices for bioanalytical applications

Use of a virtual wall valve in polydimethylsiloxane microfluidic devices for bioanalytical applications

Virtual Assembly of Ball Valve Based on Computer Supported Cooperative Design

This paper introduces how to use the AutoCAD, Pro/E,VRML, Javascript, Dreamweaver and other computer-related software to complete the virtual ball valve assembly based on Computer Supported Cooperative Design. This paper also describes some ways to resolve contradictions and problems when related software worked together.

Pulmonary regurgitation: The effects of varying pulmonary artery compliance, and of increased resistance proximal or distal to the compliance

Background Pulmonary regurgitation is common after repair of tetralogy of Fallot, predisposing to right ventricular dilatation and potentially fatal arrhythmias. Magnetic resonance studies of such patients led us to hypothesize that the amount of regurgitation, in the absence of an effective valve, depends on pulmonary arterial compliance and on the location of resistance relative to the compliance. Methods and results Using a pre-existing mathematical model representing the cardiovascular system, removal of the virtual pulmonary valve gave a triphasic pulmonary artery flow curve similar in shape to those recorded in patients with free regurgitation, with a regurgitant fraction of 30%. There was no reversal of flow at pulmonary capillary level, the regurgitant volume originating entirely from the compliance of the virtual pulmonary arteries and arterioles. Doubling their compliance increased regurgitation to 35%, whereas halving it decreased regurgitation to 23%. Doubling the total pulmonary vascular resistance by increasing arteriolar resistance increased regurgitation to 46%, whereas doubling it by simulating pulmonary annular stenosis proximal to the compliance limited regurgitation to 10%, but at the cost of a 32 mmHg peak systolic pressure drop. Conclusions The model supported our hypotheses, indicating the relevance to pulmonary regurgitation of previously overlooked variables. The virtual pulmonary regurgitation was exacerbated by pulmonary artery compliance and by elevated resistance distal to it, but was limited by more proximal resistance. These relationships merit careful clinical investigation as they would have implications for the initial management, subsequent investigation and decisions on re-intervention in patients with pulmonary regurgitation.

Supersonic Virtual Valve Design for Numerical Simulation of a Large-Bore Natural Gas Engine

In many applications of supersonic injection devices, three-dimensional computation that can model a complex supersonic jet has become critical. However, in spite of its increasing necessity, it is computationally costly to capture the details of supersonic structures in intricate three-dimensional geometries with moving boundaries. In large-bore stationary natural gas fueled engine research, one of the most promising mixing enhancement technologies currently used for natural gas engines is high-pressure fuel injection. Consequently, this creates considerable interest in three-dimensional computational simulations that can examine the entire injection and mixing process in engines using high-pressure injection and can determine the impact of injector design on engine performance. However, the cost of three-dimensional engine simulations—including a moving piston and the kinetics of combustion and pollutant production—quickly becomes considerable in terms of simulation time requirements. One limiting factor is the modeling of the small length scales of the poppet valve flow. Such length scales can be three orders of magnitude smaller than cylinder length scales. The objective of this paper is to describe the development of a methodology for the design of a simple geometry supersonic virtual valve that can be substituted in three-dimensional numerical models for the complex shrouded poppet valve injection system actually installed in the engine to be simulated. Downstream flow characteristics of the jets from an actual valve and various virtual valves are compared. Relevant mixing parameters, such as local equivalent ratio and turbulence kinetic energy, are evaluated in full-scale moving piston simulations that include the effect of the jet-piston interaction. A comparison of the results has indicated that it is possible to design a simple converging-diverging fuel nozzle that will produce the same jet and, subsequently, the same large-scale and turbulent-scale mixing patterns in the engine cylinder as a real poppet valve.

A virtual valve for smooth contamination-free flow switching

We present a channel geometry that allows for clean switching between different inlets of a microchip without any contamination of the inlets or the downstream flow. We drive this virtual valve with a pneumatic pressure setup that minimizes disturbance of the downstream flow during the switching procedure by simultaneous variation of the pressures applied to the different inlets. We assess the efficiency of the setup by spectroscopic measurement of downstream dye concentrations, and demonstrate its practical utility by sequentially constructing multiple layers of alginate hydrogel. The method is potentially useful for a whole series of further applications, such as changing perfusion liquids for cell culture and cell analysis, metering, chemical-reaction initiation and multi-sample chromatography, to name a few.

Virtual-Design-Model-Based Pressure-Tracking Control of High-Dynamic Pneumatic Valves Using a Sliding Mode Controller Combined with a Proportional-Integral-Derivative Scheme

This paper deals with the issue of pneumatic pressure-tracking control based on a virtual design model of high-dynamic valves. As a fundamental step prior to controller design, a virtual valve model is developed by defining the required parameters through analysing geometrical and material data. For validation of the virtual model, the open-loop performances of subsystems are compared with experimental results. A sliding-mode controller combining a proportional-integral-derivative scheme is developed for compensation of inherent non-linearities and thus a significant reduction in tracking error is achieved for pressure-tracking control applications.