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Injection Pressure (injection + pressure)
Selected AbstractsPressures generated in vitro during Stabident intraosseous injectionsINTERNATIONAL ENDODONTIC JOURNAL, Issue 5 2005J. M. Whitworth Abstract Aim, To test the hypothesis that the Stabident intraosseous injection is a potentially high-pressure technique, which carries serious risks of anaesthetic cartridge failure. Methodology, A standard Astra dental syringe was modified to measure the internal pressure of local anaesthetic cartridges during injection. Intra-cartridge pressures were measured at 1 s intervals during slow (approximately 15 s) and rapid (<10 s) injections of 2% Xylocaine with 1 : 80 000 adrenaline (0.25 cartridge volumes) into air (no tissue resistance), or into freshly prepared Stabident perforation sites in the anterior mandible of freshly culled young and old sheep (against tissue resistance). Each injection was repeated 10 times over 3 days. Absolute maximum pressures generated by each category of injection, mean pressures at 1 s intervals in each series of injections, and standard deviations were calculated. Curves of mean maximum intra-cartridge pressure development with time were plotted for slow and rapid injections, and one-way anova (P < 0.05) conducted to determine significant differences between categories of injection. Results, Pressures created when injecting into air were less than those needed to inject into tissue (P < 0.001). Fast injection produced greater intra-cartridge pressures than slow delivery (P < 0.05). Injection pressures rose more quickly and to higher levels in small, young sheep mandibles than in larger, old sheep mandibles. The absolute maximum intra-cartridge pressure developed during the study was 3.31 MPa which is less than that needed to fracture glass cartridges. Conclusions, Stabident intraosseous injection conducted in accordance with the manufacturer's instructions does not present a serious risk of dangerous pressure build-up in local anaesthetic cartridges. [source] The creation of an asymmetric hydraulic fracture as a result of driving stress gradientsGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2009T. Fischer SUMMARY Hydraulic fracture stimulation is frequently performed in hydrocarbon reservoirs and geothermal systems to increase the permeability of the rock formation. These hydraulic fractures are often mapped by hypocentres of induced microearthquakes. In some cases microseismicity exhibits asymmetry relative to the injection well, which can be interpreted by unequal conditions for fracture growth at opposite sides of the well or by observation effects. Here we investigate the role of the lateral change of the minimum compressive stress. We use a simple model to describe the relation among the lateral stress gradient, the mean viscous pressure gradients in the fracture wings, the fracture geometry, and the net pressure in the fracture. Our model predicts a faster fracture growth in the direction of decreasing stress and a limited growth in the opposite direction. We derive a simple relationship to estimate the lateral stress gradient from the injection pressure and the shape of the seismic hypocentre cloud. The model is tested by microseismic data obtained during stimulation of a Canyon Sands gas field in West Texas. Using a maximum likelihood method we fit the parameters of the asymmetric fracture model to the space,time pattern of hypocentres. The estimated stress gradients per metre are in the range from 0.008 to 0.010 times the bottom-hole injection overpressure (8,10 kPa m,1 assuming the net pressure of 1 MPa). Such large horizontal gradients in the order of the hydrostatic gradient could be caused by the inhomogeneous extraction of gas resulting in a lateral change of the effective normal stress acting normal to the fracture wall. [source] The role of friction and secondary flaws on deflection and re-initiation of hydraulic fractures at orthogonal pre-existing fracturesGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2006Xi Zhang SUMMARY In this study, we explore the nature of plane-strain hydraulic fracture growth in the presence of pre-existing fractures such as joints without or with secondary flaws. The 2-D plane-strain fracture studied can be taken as a cross-section through the short dimensions of an elongated 3-D fracture or as an approximate representation of the leading edge of a 3-D fracture where the edge curvature is negligible. The fluid-driven fracture intersects a pre-existing fracture to which it is initially perpendicular and is assumed not to immediately cross, but is rather deflected into the pre-existing fracture. The intersection results in branching of the fracture and associated fluid flow into the pre-existing fracture. Further growth results in opening and frictional sliding along the pre-existing fracture. Fracture propagation in an impermeable homogeneous elastic medium and fluid invasion into a pre-existing fracture are both driven by an incompressible, Newtonian fluid injected at a constant rate. The frictional stress on the surfaces of pre-existing fractures is assumed to obey the Coulomb law. The governing equations for quasi-static fluid-driven fracture growth are given and a scaling is introduced to help identify important parameters. The displacement discontinuity method and the finite difference method are employed to deal with this coupling mechanism of rock fracture and fluid flow. In order to account for fluid lag, a method for separately tracking the crack tip and the fluid front is included in the numerical model. Numerical results are obtained for internal pressure, frictional contact stresses, opening and shear displacements, and fluid lag size, as well as for fracture re-initiation from secondary flaws. After fracture intersection, the hydraulic fracture growth mode changes from tensile to shearing. This contributes to increased injection pressure and to a reduction in fracture width. In the presence of pre-existing fractures, the fluid-driven cracks can be arrested or retarded in growth rate as a result of diversion of fluid flow into and frictional sliding along the pre-existing fractures. Frictional behaviour significantly affects the ability of the fluid to enter or penetrate the pre-existing fracture only for those situations where the fluid front is within a certain distance from the intersecting point. Importantly, fluid penetration requires higher injection pressure for frictionally weak pre-existing fractures. Fracture re-initiation from secondary flaws can reduce the injection pressure, but re-initiation is suppressed by large sliding on pre-existing fractures that are frictionally weak. [source] Influence of high rates of supplemental cooled EGR on NOx and PM emissions of an automotive HSDI diesel engine using an LP EGR loopINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 15 2008A. Maiboom Abstract Previous experimental studies on diesel engine have demonstrated the potential of exhaust gas recirculation (EGR) as an in-cylinder NOx control method. Although an increase in EGR at constant boost pressure (substitution EGR) is accompanied with an increase in particulate matter (PM) emissions in the conventional diesel high-temperature combustion (HTC), the recirculation of exhaust gases supplementary to air inlet gas (supplemental EGR) by increasing the boost pressure has been suggested as a way to reduce NOx emissions while limiting the negative impact of EGR on PM emissions. In the present work, a low-pressure (LP) EGR loop is implemented on a standard 2.0 l automotive high-speed direct injection (HSDI) turbocharged diesel engine to study the influence of high rates of supplemental cooled EGR on NOx and PM emissions. Contrary to initial high-pressure (HP) EGR loop, the gas flow through the turbine is unchanged while varying the EGR rate. Thus, by closing the variable geometry turbine (VGT) vanes, higher boost pressure can be reached, allowing the use of high rates of supplemental EGR. Furthermore, recirculated exhaust gases are cooled under 50°C and water vapour is condensed and taken off from the recirculated gases. An increase in the boost pressure at a given inlet temperature and dilution ratio (DR) results in most cases an increase in NOx emissions and a decrease in PM emissions. The result of NOx,PM trade-off, while varying the EGR rate at fixed inlet temperature and boost pressure depends on the operating point: it deteriorates at low load conditions, but improves at higher loads. Further improvement can be obtained by increasing the injection pressure. A decrease by approximately 50% of NOx emissions while maintaining PM emission level, and brake specific fuel consumption can be obtained with supplemental cooled EGR owing to an LP EGR loop, compared with the initial engine configuration (HP moderately cooled EGR). Copyright © 2008 John Wiley & Sons, Ltd. [source] Systematic optimization for the evaluation of the microinjection molding parameters of light guide plate with TOPSIS-based Taguchi methodADVANCES IN POLYMER TECHNOLOGY, Issue 1 2010Te-Li Su Abstract A back light module is a key product for providing sufficient light source for a liquid crystal display (LCD). The light guide plate (LGP), used to increase the light usage rate, is a key component in the back light module. This study researches the microinjection molding process parameters and the quality performance of the LGP. Its purpose was to develop a combining Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) with the Taguchi method. This is to optimize the multiquality performance of the LGP for the injection molding manufacturing process, in which both the LCD and the LGP spontaneously produce the best quality performance for V-cut depth and angle. First, an L18 orthogonal array was planned for the manufacturing parameters that affect the microinjection molding process. These included cooling time, mold temperature, melt temperature, injection speed, injection pressure, packing pressure, packing switching, and packing time. The TOPSIS was used to deal with the single-quality optimization disadvantage of the Taguchi method. Then, the TOPSIS response table was used to obtain the optimized manufacturing parameters combination for a multiresponse process optimization. From the analysis of variance, the significant factors for the quality performance of the LGP could be obtained. In other words, by controlling these factors, it was possible to efficiently control the quality performance of the LGP. Finally, with the five verified experiments, the optimized processing parameters came within a 95% confidence interval. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 29:54,63, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20181 [source] Adaptive multiobjective optimization of process conditions for injection molding using a Gaussian process approachADVANCES IN POLYMER TECHNOLOGY, Issue 2 2007Jian Zhou Abstract Selecting the proper process conditions for the injection-molding process is treated as a multiobjective optimization problem, where different objectives, such as minimizing the injection pressure, volumetric shrinkage/warpage, or cycle time, present trade-off behaviors. As such, various optima may exist in the objective space. This paper presents the development of an integrated simulation-based optimization system that incorporates the design of computer experiments, Gaussian process (GP) for regression, multiobjective genetic algorithm (MOGA), and levels of adjacency to adaptively and automatically search for the Pareto-optimal solutions for different objectives. Since the GP approach can provide both the predictions and the estimations of the predictions simultaneously, a nondominated sorting procedure on the predicted variances at each iteration step is performed to intelligently select extra samples that can be used as additional training samples to improve the GP surrogate models. At the same time, user-defined adjacency constraint percentages are employed for evaluating the convergence of iteration. The illustrative applications in this paper show that the proposed optimization system can help mold designers to efficiently and effectively identify optimal process conditions. © 2007 Wiley Periodicals, Inc. Adv Polym Techn 26:71,85, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20092 [source] Reactive mold filling in resin transfer molding processes with edge effectsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2009Yanyu Ding Abstract Reactive mold filling is one of the important stages in resin transfer molding processes, in which resin curing and edge effects are important characteristics. On the basis of previous work, volume-averaging momentum equations involving viscous and inertia terms were adopted to describe the resin flow in fiber preform, and modified governing equations derived from the Navier,Stokes equations are introduced to describe the resin flow in the edge channel. A dual-Arrhenius viscosity model is newly introduced to describe the chemorheological behavior of a modified bismaleimide resin. The influence of the curing reaction and processing parameters on the resin flow patterns was investigated. The results indicate that, under constant-flow velocity conditions, the curing reaction caused an obvious increase in the injection pressure and its influencing degree was greater with increasing resin temperature or preform permeability. Both a small change in the resin viscosity and the alteration of the injection flow velocity hardly affected the resin flow front. However, the variation of the preform permeability caused an obvious shape change in the resin flow front. The simulated results were in agreement with the experimental results. This study was helpful for optimizing the reactive mold-filling conditions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Product Yield and Gaping in Cold-smoked Atlantic Salmon (Salmo salar) Fillets as Influenced by Different Injection-salting TechniquesJOURNAL OF FOOD SCIENCE, Issue 5 2003S. Birkeland ABSTRACT Product yield and fillet gaping severity were determined in cold-smoked Atlantic salmon fillets subjected to injection-salting. Effects of process parameter settings (brine injection pressure, number of repeated injections, needle speed, injection of brine in 1 or 2 directions, and chilled fillet resting before smoking) were tested. Repeated injections increased the yield up to 5.3% (wt/wt). Increasing injection pressure significantly increased the severity of fillet gaping in smoked fillets by 18%. Brine injection directions or needle speed did not affect smoking yield. The stability of the injection system was high. The results show that choice of process parameter settings during injection-salting affects product yield after smoking. [source] Comparison of structure development in injection molding of isotactic and syndiotactic polypropylenesPOLYMER ENGINEERING & SCIENCE, Issue 8 2002Dongman Choi A comparative study of the crystallization and orientation development in injection molding isotactic and syndiotactic polypropylenes was made. The injection molded samples were characterized using wide angle X-ray diffraction (WAXD) techniques and birefringence. The injection molded isotactic polypropylene samples formed well-defined sublayers (skin, shear and core zones) and exhibited polymorphic crystal structures of the monoclinic ,-form and the hexagonal ,-form. Considerable amounts of ,-form crystal were formed in the shear and core zones, depending on the injection pressure or on the packing pressure. The isotactic polypropylene samples had relatively high frozen-in orientations in the skin layer and the shear zone. The injection molded syndiotactic polypropylene exhibited the disordered Form I structure, but it did not appear to crystallize during the mold-filling stage because of its slow crystallization rate and to develop a distinct shear zone. The core zone orientation was greatly increased by application of high packing pressure. The isotactic polypropylene samples exhibited much higher birefringence than the syndiotactic polypropylene samples at the skin and shear layers, whereas both materials exhibited similar levels of crystalline orientation in these layers. [source] Separation, size reduction, and processing of XLPE from electrical transmission and distribution cablePOLYMER ENGINEERING & SCIENCE, Issue 4 2000C. C. White The recycling of power transmission cable insulated with crosslinked PE (XLPE) was investigated by using different methods of separation and reprocessing. Separation was attempted by thermo-chemical, thermo-mechanical and microwave-mechanical means, the latter being the most successful. A mechanism encompassing all of these was formulated. Compression molding, extrusion, and injection molding with and without preheating of the material were also investigated. It was found that by preheating the XLPE and injection molding under high injection pressure, the neat XLPE could be formed into shapes with tensile strengths equal to that of the original insulation. In view of available observations, possible mechanisms for the flow and reconsolidation of XLPE crumb are proposed and discussed. [source] Experimental Study on the Molecular Dimension and Configuration of Polymer and Its Flow Characteristics from Electrolyte EffectCHINESE JOURNAL OF CHEMISTRY, Issue 4 2009Xiangguo LU Abstract Molecular clew dimension and configuration of polymer, and flow characteristics of polymer solution were studied from electrolyte effect, by making use of dynamic light scattering (DLS), scanning electron microscopy (SEM), apparent viscosity method and core flow experiment. It can be observed that with the electrolyte concentration increasing, there exists a variation trend of "decreasing, increasing and decreasing again" to the molecular clew dimension of the polymer. The compression action of Ca2+ or Mg2+ to the double electrode layer of polymer molecules is more powerful by comparison against Na+, which results in that Ca2+ and Mg2+ have a more extensive effect on the viscosity of polymer solution, and clew dimensions and their distribution. With the electrolyte concentration increasing, the polymer molecular configuration of multi-layer stereoscopic random reticulation transformed into a dendritic one. During the succeeding water flooding, the variation degree of injection pressure of core was mainly determined by the swelling extent of molecular clew of retained polymer and the produced amount of polymer. And the bigger the molecular weight of polymer is, the stronger the compression or swelling action of electrolyte to the molecule clews is, and the greater the increasing degree of injection pressure during succeeding water flooding is. The greater difference of electrolyte concentrations in used water between polymer flooding and succeeding water flooding can result in greater increasing degree of injection pressure during the succeeding water flooding. So, an advisable increasing in difference of electrolyte concentrations in used water between the polymer flooding and succeeding water flooding was proposed when designing the polymer flooding performance in oilfields, which has promising result for improving effect of polymer flooding. [source] The Effects of Casting Temperature on the Glass Formation of Zr-Based Metallic Glasses,ADVANCED ENGINEERING MATERIALS, Issue 12 2009Jie Mao Abstract The glass1-forming ability of two alloys, Zr64.9Al7.9Ni10.7Cu16.5 and Zr47Cu37.5Ag7.5Al8, prepared by arc-melting a mixture of Zr, Cu, Al, Ni and Ag elements is studied as a function of casting temperature. Other processing parameters such as the alloy melt mass, and the vacuum and injection pressures during the copper-mold-casting process are kept constant so just the influence of the casting temperature is considered. The casting temperature determines the characteristics of the liquid melt and the cooling rate. The glass-forming ability is discussed in terms of dissipation of pre-exiting, metastable local-ordering clusters that act as nucleation sites promoting crystallization, the cooling rate at high casting temperatures, and the presence of oxygen in the alloys, which is increased at high casting temperatures. It is found that the glass-forming ranges of alloys shrink as the glass-forming size approaches a critical value. The optimum temperatures are around 1450,K and 1550,K for Zr64.9Al7.9Ni10.7Cu16.5 and Zr47Cu37.5Ag7.5Al8 alloys respectively. The alloys were studied by XRD, TEM, oxygen-level determination, and DSC. [source] Kinetics of Calcium Carbonate (CaCO3) Precipitation from a Icel-Yavca Dolomite Leach Solution by a Gas (Carbon Dioxide)/Liquid ReactionHELVETICA CHIMICA ACTA, Issue 3 2009Mehmet Yildirim Abstract The effects of time, CO2 -gas-injection pressure, and bulk temperature on the precipitation of Ca2+ ions as a precipitated calcium carbonate (PCC) from a dolomite leach solution were investigated. Precipitation periods from 1 to 7,min were examined, and experiments were run at CO2 -injection pressures of 200,800,kPa. Effects of bulk temperature were studied in the range from 40 to 70°, and precipitation rates of PCC were determined by measuring the Ca2+ concentrations in the initial and effluent solutions. Influences of these parameters on the subsequent incorporation of Mg2+ ions with the precipitate are discussed in detail. Kinetic analysis of the precipitation was performed by considering the rates as a function of CO -ion concentrations. Results obtained by this process clearly show that Ca2+ ions in the solution can successfully be precipitated as a calcium carbonate product containing 54.70% of CaO and 0.77% MgO, at the rate of 2.01,mM h,1. [source] | |||||||||||||