Home About us Contact
|
Home About us Contact | ||
|
|
||
Gas Injection (gas + injection)
Selected AbstractsReduced Models of Impurity Seeded Edge PlasmasCONTRIBUTIONS TO PLASMA PHYSICS, Issue 1-3 2008D. Kh. Abstract The reduced descriptions of the distribution of impurities over ionization states, radiation losses and plasma dynamics are reviewed. Two and three most important ion approximation for light impurities and continuous descriptions of heavy impurities are discussed. Reduced descriptions of atomic processes like ionization, photo- and dielectronic recombination rates as well as of radiation abilities are proposed. As it shown, thermal forces, final relaxation times of impurity distributions over ionization states, charge-exchange and opacity effects must be taken into account in reduced models, especially for ITER problems. Linear and nonlinear stages of the radiation-condensation mode as well as some aspects of disruptions and noble gas injection into tokamak plasmas are analyzed with the reduced models. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A Practical Approach to the Design, Monitoring, and Optimization of In Situ MTBE Aerobic BiobarriersGROUND WATER MONITORING & REMEDIATION, Issue 1 2010Paul C. Johnson A paradigm for the design, monitoring, and optimization of in situ methyl tert -butyl ether (MTBE) aerobic biobarriers is presented. In this technology, an oxygen-rich biologically reactive treatment zone (the "biobarrier") is established in situ and downgradient of the source of dissolved MTBE contamination in groundwater, typically gasoline-impacted soils resulting from leaks and spills at service station sites or other fuel storage and distribution facilities. The system is designed so that groundwater containing dissolved MTBE flows to, and through, the biobarrier treatment zone, ideally under natural gradient conditions so that no pumping is necessary. As the groundwater passes through the biobarrier, the MTBE is converted by microorganisms to innocuous by-products. The system also reduces concentrations of other aerobically degradable chemicals dissolved in the groundwater, such as benzene, toluene, xylenes, and tert -butyl alcohol. This design paradigm is based on experience gained while designing, monitoring, and optimizing pilot-scale and full-scale MTBE biobarrier systems. It is largely empirically based, although the design approach does rely on simple engineering calculations. The paradigm emphasizes gas injection,based oxygen delivery schemes, although many of the steps would be common to other methods of delivering oxygen to aquifers. [source] Behaviour of refrigerant mixtures with gas/liquid injectionINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 14 2003Samuel M. Sami Abstract In this paper, the impact of gas/liquid injection on the behaviour of new alternative refrigerant mixtures such as; R-410A, R-507, R-407C, and R-404A are discussed, analysed and presented. The test results were obtained using an air,source heat pump set up with enhanced surface tubing heat exchanger under various gas/liquid injection ratios. Performance tests were conducted according to the ARI/ASHRAE Standards. The performance data demonstrated that as gas/liquid injection increases compressor head pressure and discharge temperature decrease and this has a positive effect in protecting the compressor. The effect of gas/liquid injection on mixture behaviour varies from mixture to another depending upon the mixture composition. Furthermore, hot gas injection appears to have a significant and positive influence on the COP. The performance of refrigerants R-407C and R-404A has been enhanced with 5% gas injection and mix of gas and liquid 5% injection, respectively. The data presented in these figures also show that other hot gas injection ratios and gas/liquid mix degrade the heat exchanger performance. Copyright © 2003 John Wiley & Sons, Ltd. [source] Determination of in-plane permeability of fiber preforms by the gas flow method using pressure measurementsPOLYMER COMPOSITES, Issue 1 2003Sun K. Kim A method is described for measuring the in-plane permeability of orthotropic fibrous preforms using gas flow. The method is based on an optimization process between computed and measured pressures at various locations in the mold during steady state gas flow through the enclosed preform. The computed pressure is obtained by the control volume finite element method (CVFEM). This method was demonstrated by using a specially designed mold with multiple ports for gas injection and pressure measurement and it was shown that it can be implemented easily and yields consistent and reliable results. [source] Gas assisted injection molding of a handle: Three-dimensional simulation and experimental verificationPOLYMER ENGINEERING & SCIENCE, Issue 8 2005A. Polynkin Methods implemented in a three-dimensional finite element code for the simulation of gas assisted injection molding are described, and predictions compared with the results of molding trials. The emphasis is on prediction of primary gas penetration and plastic wall thickness, including the effects of cooling during a delay before gas injection. For the latter, time dependent heat transfer coefficients at the cavity surface are used, determined in a separate analysis of transient heat conduction through the plastic and the mold tool to the circulating coolant. This shows how the initial value of 25,000 W/m2K falls by about an order of magnitude during the first few seconds of cooling, and also how values vary from cycle to cycle as steady periodic conditions are approached. For a tubular handle molded in polystyrene, with melt flow modeled by a Cross WLF model, comparisons of simulations with sectioned parts show excellent prediction of wall thickness and its variation circumferentially and in bends. The increase in wall thickness due to cooling during a gas delay is accurately modeled, as is the occurrence of a blow out. POLYM. ENG. SCI. 45:1049,1058, 2005. © 2005 Society of Plastics Engineers [source] 1233: How to choose the best surgical procedure?ACTA OPHTHALMOLOGICA, Issue 2010CJ POURNARAS Purpose Dealing to the localization and sealing retinal breaks, the surgical success rate for the cure of rhegmatogenous retinal detachment greatly changed with the introduction of scleral buckling (SB), intraocular gas injection, and pars plana vitrectomy (PPV). Methods In localized cases, pneumatic retinopexy and scleral buckling surgery (SB) remains the most popular surgical methods. Complicated cases with PVR grade B or C, giant tears, or macular holes are most commonly treated with primary pars plana vitrectomy. A large group of rhegmatogenous RDs with medium severity that comprise about 30% of all primary rhegmatogenous RDs in the Scleral Buckling versus Primary Vitrectomy in Rhegmatogenous Retinal Detachment recruitment study, were treated by SB and PPV. Advances in vitrectomy instrumentation and wideangle imaging systems have increased the popularity of PPV. Results The decision by the surgeon to use scleral buckling rather than PPV depends on a number of factors, including the lens status, size and location of breaks, patient compliance, and individual experience. Initial PPV may be successful for phakic patients. However, the SPR study shows a benefit of SB in phakic eyes with respect to BCVA improvement. Although no difference in BCVA was demonstrated in the pseudophakic trial, PPV was recommend for pseudophakic RD based on a better anatomical outcome. Conclusion There was a significant trend towards more frequently employing primary PPV (with or without SB) for the management of primary RRD. A significant improvement in the primary success rates for RD, were shown for all retinal surgical modalities applied for the treatment of rhegmatogenous retinal detachment. [source] 2145: Descemet´s membrane detachment 16 years after PK and 10 months after phacoACTA OPHTHALMOLOGICA, Issue 2010JO FERNANDEZ MENDY Purpose The purpose of this paper is to present an unusual case of DMD and analyze this complication Methods A 57-year-old woman, who had bilateral keratoconus, underwent three penetrating keratoplasties (PK) on her RE in 1981, 1993 and 1995 resulting in ptisis bulbi. In her LE she underwent two PK (1981, 1994) follow by arcuate incisions (1995) and an uneventful phacoemulsification in 2007. 10 months after cataract surgery, she begun with blurred vision, the BCVA was 20/400 and was seen by 3 ophthalmologists who made the diagnosis of endothelial failure and suggested a new PK or a DSAEK. We performed an Optical Coherence Tomography, diagnosing a complete Descemet´s membrane detachment (DMD). An intracameral gas injection of C3F8 at 16% was performed in the operating room, and the patient was instructed to maintain a supine position. After 24 hours VA improved to 20/80 and after 72 hours 20/30 UCVA. A small bubble was present in the anterior chamber for more than 3 weeks. One month later she achieved 20/20 with Contact Lens. During the first year after reattachment it was necessary to change the CL due to an increasing with the rule astigmatism from 3D to 5D. Results Two years after gas injection BSVA is 20/25 because she is no longer using CL, Descemet´s membrane still remains well attached, even thought we realized that there was a trend to steepen the vertical meridian due to the widening of a nasal arcuate incision, that we think was the origin of the DMD. Conclusion DMD is a rare complication of Phacoemulsification, seen immediately after the surgery. So far there has not reported any complete DMD after phaco after PK. We think that it is mandatory to perform a corneal OCT in all cases of PK and stromal edema; it could probably be a DMD. [source] Face down posturing for macular hole surgery.ACTA OPHTHALMOLOGICA, Issue 2009Is it really required? Purpose Background: In macular hole surgery pars plana vitrectomy and intravitreal gas injection with or without inner limiting membrane peel, is considered the mainstay of treatment. The requirement for face down posturing is generally regarded as part of the traditional postoperative routine. Several mechanisms have been postulated to explain the action of the gas bubble including exertion of a large floatation force on the macula and prevention of the macular hole exposure to vitreous fluid. Recently the need to face down has been chalenged since this regime compromises patients' postoperative quality of life and it makes macular hole surgery almost impossible for individuals with mental or physical limitations. Methods Review of personal data and systermatic literature review of studies investigating macular hole surgery with shortened or eliminated face down posturing. Results There is considerable body of evidence suggesting successful anatomical and functional outcome in patients with shorter duration of posturing or no posturing at all following macular hole surgery. The pros and cons of each technique will be presented in detail. Conclusion Prone posturing following macular hole surgery provides no functional or anatomic benefit but it is associated with slower progression of cataract. Combined phacovitrectomy without face down positioning may be considered for phakic patients undergoing macular hole surgery. [source] PaCE: a technique to avoid subretinal fluid drainage in retinal detachment surgeryACTA OPHTHALMOLOGICA, Issue 1 2006Manzar Saeed Abstract. Purpose:,Subretinal fluid (SRF) drainage and thus the potential complications of this procedure during scleral buckling can be avoided by inducing SRF absorption preoperatively. The technique described in this series is named PaCE (Pneumatic Cryo Explant). Methods:,A total of 22 eyes of 22 patients with primary bullous rhegmatogenous retinal detachment (RRD) were included in this prospective non-comparative case trial. All satisfied specific inclusion criteria similar to those used in previous pneumatic retinopexy (PR) studies. Under direct visualization, 0.3 ml C3F8 100% was injected into the vitreous cavity through the pars plana. Postoperative posturing was encouraged. Retinopexy with either cryotherapy or laser was performed, combined with scleral buckling (SB) when the SRF was absorbed. Avoidance of SRF drainage and persistent reattachment of the retina at the end of the 12-month follow-up was considered a successful outcome. A change in vision by one line (logMAR) was considered significant. Results:,Resolution of SRF before retinopexy and the SB procedure was achieved in 20 of 22 eyes (90.9%) and hence SRF drainage was not required. Visual improvement was achieved in 95% of cases. One eye (4.5%) lost vision due to a total RD after gas injection (further surgery was not carried out). Conclusion:,PaCE should be considered in any suitable case of primary RRD where SRF drainage is deemed necessary. The potential complications associated with this procedure are relatively less serious and it does not compromise the viability of subsequent procedures. [source] | |||||||||||||