Seal Mechanism Research Articles

Commentary on ‘The Best Conditions for Parallel Stenting during EVAR: An In Vitro Study’

1078-5884/$ e see front matter 2012 European So http://dx.doi.org/10.1016/j.ejvs.2012.08.006 The concept of the chimney graft (CG) was first introduced by Greenberg et al1 with the use of renal stents to depress the proximal edge of stent graft fabric that protruded a few millimetres above the renal artery ostium. The CG involves concurrent deployment of a standard aortic endograft and covered stents into the visceral arteries such that the proximal portion of the visceral stent lies parallel to the aortic stent with the distal portion preserving flow to the overstented visceral vessel. Indications for this technique include restoration of flow in aortic branches accidentally or intentionally covered during endovascular aneurysm repair (EVAR) when the aneurysm neck is too short to provide adequate seal, and the SG needs to be placed across the aortic branches. This is particularly true in urgent cases when it is not possible to delay for the manufacture of a branched/fenestrated graft, which otherwise would be indicated, such as symptomatic or ruptured abdominal aortic aneurysms. It is also significantly cheaper than branched/fenestrated endografts. Evidence surrounding the use of CG consists of case reports and small case series only and the long-term durability of the CG remains unclear. Intuitively they have design flaws compared to branched/fenestrated grafts. The contact of the endograft to the vessel wall may be decreased by the visceral grafts; subsequently there is a poorer graft/wall interface and therefore a reduction in the radial sealing force. “Gutters” between the vessel wall, the stents, and the endografts may be difficult to seal and lead to subsequent endoleaks. The mechanism of seal around the CG stents and gutters is likely to be multifactorial.

A double auction model for competitive generators and large consumers considering power transmission cost

The pricing mechanism in a deregulated electricity market is consistently a critical issue to improve market operations. Along with the development of electricity market, large consumers may purchase electric power from generators directly. In this paper, with an effort to introduce McAfee’s second-price sealed auction mechanism into multi-unit electric power transaction between competitive generators and large consumers, an auction model is developed to decide electric power price between competitive generators and large consumers based on the inclusion of the transaction cost and power transmission cost in a wholesale electricity market. After the description of pricing rules in the deregulated power market, auction rules and transaction rules are discussed. In particular, auction rules can increase the probability that generators providing a large number of supply and large consumers with high demand win the auction. On the other hand, transaction rules can optimize the whole transmission cost and transaction cost under market equilibrium, and the whole system is dispatched to maximize social welfare. A numerical example with eight suppliers and eight large consumers is provided to illustrate the essential features of this method.

Sealed bid auctions versus ascending bid auctions: an experimental study

This paper considers two multi-item auction formats (ascending and sealed bid) which both identify the minimum Walrasian equilibrium prices and where truthful preference revelation constitutes an equilibrium. Even though these auction formats share many theoretical properties, there are behavioral aspects that are not easily captured. To explore this issue in more detail, this paper experimentally investigates what role the design of the auction format has for its outcome. The results suggest that the sealed bid mechanism performs weakly better in all of the investigated measures (consistent reporting, efficiency etc.). In addition, we find that the performance of the ascending auction is increasing over time, whereas the sealed bid auction shows no such tendency.

Production-induced fault compartmentalization at Elk Hills field, California

Mature and aging clastic-dominated hydrocarbon fields commonly become increasingly difficult to produce, causing lower economic return than initially forecast. A major cause of this reduced economic viability is compartmentalization, defined as limitation on the ability to produce hydrocarbons resulting from permeability barriers within a field. Three primary causes of compartmentalization are structural variations in permeability, stratigraphic variations in permeability, and permeability reduction resulting from compaction adjacent to producing wellbores. Recognition and delineation of compartmentalization permit formulation of development and depletion plans to maximize recovery and economic value. Here, we examine one of 52 reservoir-scale faults that compartmentalize the eastern shallow oil zone (ESOZ), Elk Hills field, California. Using well-log, stratigraphic, structural, and pressure data, we apply standard fault seal analyses to the selected fault. Results are compared with known pressure conditions across the fault and show the fault capable of supporting pressure differentials two to three times those expected from standard static fault seal measures. Although this observation could be used as a basis for local calibration of standard fault seal measures for a dynamic seal, such an approach assumes that these fault seal mechanisms are in fact the cause of sealing behavior. Alternatively, one of the most significant changes in ESOZ reservoir conditions over the production lifetime of the field is the reduction of fluid pressure from approximately 1500 to approximately 200 psi (from ∼10.27 to ∼1.37 MPa). Decreasing fluid pressure would have driven stress states acting on faults in the reservoir from critical (near or at slip) to stable (nonslipping) conditions. Critically stressed faults and fractures are more transmissive than those that are noncritically stressed. We propose that decreasing fluid pressure can cause faults to become less leaky, causing production-induced reservoir compartmentalization.

Block Mechanism of Microclearance Block Liquid and Lifting Height Calculating

Mechanical seal mechanism was applied to study block mechanism of gaswell microclearance block liquid for the first time, which explained block mechanism of microclearance block liquid. The paper has built a block physical model of microclearance block liquid and has got calculation formulas of the block liquid lifting height. Then the block liquid lifting heights were calculated and analyzed in different microclearance widths and pressures. The sealing effect of the block liquid was discussed. The analyzed results showed that sealing effect of the block liquid was very obvious when microclearance width was lesser than 12μm. The paper not only enriched the study on block mechanism of gaswell microclearance block liquid but also proposed theoretical guidance to solve radically gas migration problem of micro-annulus.

Prototype of Manipulator for Micro Objects Employing AZARASHI (Seal) Mechanism as Mobile Platforms

This paper deals with an application of a small mobile device, “AZARASHI (seal) Mechanism” to a micromanipulation device. Pick-and-place tasks are very important in small-size-part manufacturing, printedcircuit board testing and biotechnological operations. A prototype of themicromanipulation device with four degrees of freedom was built. The device consists of an L-shaped AZARASHI device for thex-,y- and θ- motions, and a one-degree-of-freedom device used for thez-motion as mobile platforms. By an automatic sequence under visual feedback, glass beads were manipulated. A bright point observed with a videomicroscope was used instead of a target marker to position the stage for flexible usage. In order to trap a small glass bead, the air was gently sucked through a glass capillary. The stage was controlled to track the bright point by a binary image. Then the bead was placed by releasing the pressure to atmospheric one. Error factors were discussed through the evaluation of each step. The positioning accuracy of the stage was within 1 pixel. Adhesion of the beads on the capillary mainly decreased the total positioning accuracy.

Parametric Study on a Wavy-Tilt-Dam Mechanical Face Seal in Reactor Coolant Pumps

The reliability of mechanical seals in reactor coolant pumps is essential for the safety of pressurized water nuclear power plants. A wavy-tilt-dam (WTD) mechanical face seal, characterized by a circumferential wave with a radial taper and seal dam on one of the seal faces, has proved to be effective in practice. A theoretical model is developed to study the mechanism of the WTD seal in this article. Then, the structural parameters such as wave amplitude, taper, dam radius, and the number of waves are studied for the WTD seal under different rotation speeds and seal pressures. The results show that the mechanism of the WTD seal is the combination of hydrodynamic and hydrostatic effects, which do not work simultaneously. During the period of start-up and shutdown, when the film thickness and the pressure differential are both small, the seal works as a hydrodynamic seal, whereas it is a nearly hydrostatic seal at the stable working condition. The waves on the seal face will obviously impair the hydrostatic effect before cavitation occurs in the fluid film. The optimal values of the structure are obtained by analyzing the numerical results under certain working conditions. In addition, the performance varies obviously with rotation speed and seal pressure.

Low-Cost Aerosol Exposure System for Guinea Pigs

This project designed and tested an economical apparatus to safely expose guinea pigs to biohazardous aerosol. The goals were to design a system that can be easily decontaminated, fits in a biosafety cabinet, and affordable. It is composed of three main chambers housed in an outer box that fits within a conventionally sized biosafety cabinet. The animal chamber contains a removable housing unit for either four or eight guinea pigs. The aerosol chamber is separate to minimize contamination. The nebulizer chamber is also sealed to reduce risks from leakages. This apparatus is easily decontaminated by immersion in disinfectant. This system has been tested for safety, ergonomics, efficiency of rodent exposure to bacteria, airflow, access points, seal mechanisms, and size. This system is effective, consistent, safe and cost efficient.

Analysis and Experimental Study on Magnetic Fluid Seal Mechanism

The authors put forward a new design of experimental setup in order to study the mechanism of magnetic fluid seal, and used Ansys to simulate the magnetic field distribution in the setup, the results prove its rationality. The experiment to study the way of pressure transmission has been done on the experimental setup. The experimental conclusion shows that pressure transmission is based on the recoverability of the magnetic fluid seal. When pressure exceeds the ability of the seal stage, there is a leak path in the magnetic fluid, and then the gas flows to the next stage, after that, the leak path disappears. Pressure transmits from one seal stage to the next one in this way.

An Auction Theory Based Algorithm for Throughput Maximizing Scheduling in Centralized Cognitive Radio Networks

In this letter we propose an auction theory based algorithm for throughput maximizing scheduling in centralized cognitive radio networks (CRN). In the considered CRN scheme, a centralized base station coordinates the assignment of frequencies and time slots to cognitive users with multiple antennas. Our proposed algorithm uses first-price sealed bid auction mechanism in which frequency and time slot pairs are considered as the auctioned resources and cognitive users are the bidders. The experimental results show that our computationally efficient algorithm yields very close throughput performance to the optimization software CPLEX values.

Optimization design for mechanical seals in reactor coolant pumps based on a fluid–solid strong-interaction model

The study on the mechanism and performance of the mechanical seals in reactor coolant pumps (RCPs) is very important for the safe operations of pressurized water reactor power plants. By exploring the operating mechanism of the first seal of the hydrostatic mechanical seal in RCPs, an analytical fluid–solid strong-interaction model of the seal is proposed in this article. The model holds that the mechanical deformations of the seal assembly are dominated by the deflections of the seal rings, and this idea is demonstrated by the numerical simulation result of a fluid–solid interaction (FSI) model. Using the analytical FSI model, the regularity that the leakage rate of the first seal varies with the differential pressure in a RCP is obtained, and compared with the operational data, which is used to verify the model. Based on the understanding of the reliability of the seal, a dimensionless parameter Λ that acts as an attribute to the reliability is proposed in this article. Using the analytical FSI model and Λ as the optimization algorithm and optimization object, respectively, the optimum designs about the seal faceplateconfigurations are performed. Also, the specific optimization conclusions are given simultaneously.

S112032 流体動圧軸受端部に設けられたテーパーシールに関するメカニズムの解明 : 衝撃を受けたときのテーパーシールにおける流体表面の挙動([S11203]機械要素の設計・製造・応用技術(3))

To clarify the mechanism of the taper seal at the end of the fluid dynamic bearing used in the spindle motor of a hard disk drive, the behavior of the fluid surface in the seal when subjected to a shock is analyzed and solved. As a multi-phase flow, the behavior of the fluid surface in the seal is analyzed and numerically solved by using VOF method in consideration of the response of the rotor, the inertia force and the surface tension acting on the fluid, and the influence of the pressure from the bearing. The influences of the eccentricity of the rotor, the oil barrier film coated on the seal wall, the shock strength and the taper seal shapes on the behavior of the fluid surface are discussed. As a result, it is clarified that decreasing the eccentricity of the rotor, decreasing the mass of the rotor, increasing the stiffness and damping of the bearing, making a suitable seal shape are effective countermeasures against lubricant leakage from the seal.

Sealed Bid Auctions vs. Ascending Bid Auctions: An Experimental Study

This paper considers the sealed bid and ascending auction, which both identifies the minimum Walrasian equilibrium prices and where truthful preference revelation constitutes an equilibrium. Even though these auction formats share many theortical properties, there are behavioral aspects that are not easily captured. To explore this issue in more detail, this paper experimentally investigates what role the design of the auction format has for its outcome. The results suggest that the sealed bid mechanism performs weakly better in all of investigated measures (consistent reporting, efficiency etc.). In addition, we find that the performance of the ascending auction is increasing over time, whereas the sealed bid auction shows no such tendency.

Prediction markets: an experimental approach to forecasting cattle on feed

PurposeThe purpose of this paper is to use prediction markets to forecast an agricultural event: United States Department of Agriculture's number of cattle on feed (COF). Prediction markets are increasingly popular forecast tools due to their flexibility and proven accuracy to forecast a diverse array of events.Design/methodology/approachDuring spring 2008, a market was constructed comprised of student traders in which they bought and sold contracts whose value was contingent on the number of COF to be reported on April 18, 2008. During a nine‐week period, students were presented three types of contracts to forecast the number of COF. To estimate forecasts a uniform price sealed bid auction mechanism was used.FindingsThe results showed that prediction markets forecasted 11.5 million head on feed, which was about 1.6 percent lower than the actual number of COF (11.684 million). The prediction market also fared slightly worse than analysts' predictions, which on average suggested there would be about 11.795 million head (an over‐estimate of about 1 percent).Originality/valueThe contribution of this study was not to provide conclusive evidence on the efficacy of using prediction markets to forecast COF, but rather to present an empirical example that will spark interest among agricultural economists on the promises and pitfalls of a research method that has been relatively underutilized in the agricultural economics literature.

Efficiency- Reinforcement Technology Study for Hydraulic Reciprocating Sealing Based on TRIZ S-Field Analysis

The dynamic seal mechanism of hydrodynamic reciprocating sealing is discussed. TRIZ S-Field model and standard solutions is proposed. The reliability and effectivity S-Field models of hydrodynamic reciprocating sealing are constructed according to typical hydrodynamic reciprocating sealing configuration shapes, such as O-ring sealing, Y-ring sealing and polymer sealing. The leakage and failure problems solutions of hydrodynamic reciprocating sealing as well as their configuration realization are studied based on TRIZ S-Field analysis and standard solutions, which offer powerful theoretic guides for efficiency-reinforcement technology of hydrodynamic reciprocating sealing.

Influence of Slope Angle and Traction Load on Performance of AZARASHI (Seal) Mechanism with One Degree of Freedom

AbstractThis paper deals with the influence of a friction force on a small mobile device, AZARASHI (Seal) mechanism with a 1‐degree of freedom (DOF) in the cases of moving on a slope and drawing a load. This device has a piezoelectric actuator, electromagnet CA that applies a constant friction force and electromagnet CB alternating the friction force by on‐off control. AZARASHI mechanism has the same structure as the inchworm‐like mover. However, AZARASHI mechanism has a smaller number of actuators to be controlled and is driven by a smaller number of steps than the inchworm‐like mover. The motion performance on the slope from 0 to 90 degrees was experimentally investigated using a 1‐DOF device. In addition, the relationship between the displacement on a vertical plane and the friction forces was tested. Under a set of sufficient friction forces, this device was possible to climb even on the vertical plane. The traction load capacity of the 1‐DOF device was also investigated. As a result, the friction forces restricted the traction load capacity. Finally, its traction load capacity was compared with the inchworm‐like mover. The lowest friction force to hold each device restricted their displacement. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Seal indication mechanism for containers

Seal indication mechanism for containers

Computer Aided Modeling and Deign of a New Magnetic Sealing Mechanism in Engineering Applications

This article introduces a new type of magnetic sealing mechanism that reduces the lubrication oil pollution and media gaseous leakage in general reciprocating machinery including air compressors and refrigerators. The feasible function and reliable performance of this new sealing mechanism are introduced and analyzed in this paper. The computer aided design, modeling and analysis are being used to study this new sealing mechanism, and the prototype of this sealing mechanism is being tested. The study indicated the proper function of this sealing mechanism. The major advantages of this sealing mechanism include: improved sealing capacity to prevent the gaseous leakage and oil leakage, simple and compact in structure, lower precision requirement on surfaces of reciprocating pistons and shafts in production and manufacturing, and longer services in sealing life span. Also there is almost no frictional loss during the reciprocating motion of piston or shaft.

Performance of AZARASHI (Seal) Positioning Mechanism with Friction Control by Inertial Force

This paper deals with the mobility of AZARASHI (Seal) Mechanism in vacuum. A device of AZARASHI Mechanism with one degree of freedom moves by using the controlled Friction device and one to generate a constant friction. Electromagnets, springs and clamps with piezoelectric actuators have been used for the controlled Friction device. In this paper, the friction was controlled by the perpendicular inertial force using a piezoelectric actuator applied a modified trapezoidal wave. The inertial force on Friction devices restricted the driving frequency of Extension device. In the case of using stainless steel for the device and aluminum for the base, the device stably moves without adhesion.

Stratigraphic and structural compartmentalization of dryland fluvial reservoirs: Triassic Heron Cluster, Central North Sea

Abstract This paper describes the nature and relative significance of stratigraphic and structural compartmentalization in dryland fluvial reservoirs using data drawn from the Heron Cluster (Heron, Egret and Skua) oil fields in the UK Central North Sea. The Triassic Skagerrak Formation reservoir in these fields was deposited in a variety of dryland terminal fluvial settings, ranging from relatively arid terminal splay and playa to more vegetated, channel-confined systems with associated floodplain and palustrine facies. Laterally extensive floodbasin shales punctuate this terminal fluvial architecture. Static and dynamic data indicate that these fields are compartmentalized: geochemical data indicate significant fluid variations both between wells and vertically within individual wells; material balance calculations suggest production from restricted connected volumes, locally from a subset of the range of oils present; and re-perforation across significant shale boundaries access undepleted reservoir with different fluid compositions. Lateral variations could be ascribed to prominent structuration within these fields, but in general these high net:gross reservoirs do not have a viable fault seal mechanism. Early (syn-halokinetic) grounding of Triassic ‘pods’ between salt swells during salt withdrawal has resulted in zones of intense faulting along the zone of contact of the pod and the underlying basement, and also on the flanks of pods as the margins collapsed under further salt withdrawal. This deformation occurred under relatively shallow burial depths and is largely expressed by disaggregation zones and phyllosilicate fault rocks. Fault property averaging algorithms (e.g. shale gouge ratio), indicate that the sands should communicate across the juxtapositions, implying that the fluids and pressures should equilibrate between reservoir sands. However, the stratigraphic differences across major shales in both fluid geochemistry and pressure caused by draw-down are preserved despite the presence of these faults. The preservation of stratigraphic compartments indicates that for these faults the deformation mechanism was probably dominated by clay smear, in which the shale-prone sequence was smeared down the fault planes without losing its coherence. This style of stratigraphic compartmentalization occurs across several shale-prone intervals that are correlatable across the region. In some cases these mark the boundaries to major changes in fluvial depositional character, provenance and floodplain drainage, suggesting an extrinsic control that led to shale packages defining consistent barriers in all the fields. Other shale barriers do not show major changes in depositional character and, although correlatable, appear to be the product of semi-regional advance and retreat of the fluvial systems, possibly combined with nodal avulsion. In contrast to reservoirs deposited by large exorheic rivers, the terminal nature of these dryland fluvial systems appears to have resulted in the repeated interfingering of fluvial and floodbasin facies over a scale of many tens of kilometres. As a result such terminal fluvial reservoirs are prone to stratigraphic compartmentalization. However, thinner shales are prone to breaching by fluvial erosion and as a result not all correlatable shale events form barriers and only a subset will compartmentalize. Mitigation against this compartmentalization requires a development strategy where well trajectory and perforation maximizes stratigraphic exposure.