Modelling outflow following rupture in pipeline networks

A numerical model for simulating the fluid dynamics following rupture in pressurised pipeline networks containing multi-component hydrocarbon mixtures is described. Based on the solution of the conservation equations using the method of characteristics, the model accounts for pipeline bends, branches and couplings. Modelling of hypothetical full bore ruptures in straight and branched pipelines indicate the importance of accounting for pipeline system configuration complexity when simulating such type of failure.     

Modifications to the Zener formula for limitation of grain size

An experimental investigation of the ratio of grain boundary curvature to grain size is reported, from which it is deduced that the terminal grain size determined by inclusions should be about an order of magnitude less than that predicted by the Zener formula in its usual form. It is demonstrated that the Zener formula does not necessarily include the condition that each boundary is impeded by an inclusion, and a supplementary condition is derived to cover this possibility.     

Covalent immobilization of penicillin G acylase onto amine-functionalized PVC membranes for 6-APA production from penicillin hydrolysis process. II. Enzyme immobilization and characterization

This article describes the covalent immobilization of penicillin G acylase (PGA) onto glutaraldehyde-activated NH₂-PVC membranes. The immobilized enzyme was used for 6-aminopenicillanic acid production from penicillin hydrolysis. Parameters affecting the immobilization process, which affecting the catalytic activity of the immobilized enzyme, such as enzyme concentration, immobilization's time and temperature were investigated. Enzyme concentration and immobilization's time were found of determine effect. Higher activity was obtained through performing enzyme immobilization at room temperature. Both optimum temperature (35°C) and pH (8.0) of immobilized enzyme have not been altered upon immobilization. However, immobilized enzyme acquires stability against changes in the substrate's pH and temperature values especially in the higher temperature region and lower pH region. The residual relative activities after incubation at 60°C were more than 75% compared to 45% for free enzyme and above 50% compared to 20% for free enzyme after incubation at pH 4.5. The apparent kinetic parameters K_M and V_M were determined. K_M of the immobilized PGA (125.8 mM) was higher than that of the free enzyme (5.4 mM), indicating a lower substrate affinity of the immobilized PGA. Operational stability for immobilized PGA was monitored over 21 repeated cycles. The catalytic membranes were retained up to 40% of its initial activity after 10.5 working h. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Performance Analysis of Free Space Optical Networks Using the Beta-Average Recursive Estimator

The present paper aims to investigate and analyze the performance of a point-to-point optical network under a free-space optical (FSO) communication system. Free-space optical communication is a sophisticated technique that has been employed as a channel model of optical wireless communication to transfer large amounts of data at high speeds. However, two important issues, that could affect the source of the FSO link, have been added. The first one is related to chromatic dispersion which is attributed to the chirping phenomenon of the optical signal; the second issue concerns the secondary jamming power that can be generated by some Radio Frequencies from base stations. It is important to note that the effects of atmospheric turbulence, misalignment fading, and atmospheric attenuation as well as geometric losses were also taken into account. The purpose of this research work is to overcome these effects, in order to increase the data transmission rate from 1.25 to 50 Gbps in the proposed system. Consequently, a very efficient solution is suggested to correct these problems and to make the FSO link more reliable using the Beta-Average Recursive Estimator. In addition, the numerical results obtained are presented for the purpose of validating our proposal through the evaluation of the performance of a transmission link in terms of the bit error rate and Q-factor. In the end, the resulting conclusions are listed, explained and discussed.

     

Effective enhancement of electric and magnetic properties of PMMA/LiFe5O8 nanocomposites via magnetic treatment

Journal of Materials Science: Materials in Electronics - The present study presents a facile effective method to enhance the electric as well as the magnetic properties of polymer/ferrite...     

Electrografting of a biodegradable layer as a primer adhesion coating onto a metallic stent: in vitro and in vivo evaluations

Drug-eluting stents have been developed to reduce the risk of restenosis after angioplasty. To facilitate the adhesion of a poly(lactic acid) (PLA) overlayer loaded with rapamycin (20 wt%), a biodegradable macromonomer based on poly(lactic acid) (HEMA-PLA) was grafted onto the metallic stent by electrografting in a one-step reaction involving the immobilization of aryl diazonium onto the metal followed by an in situ surface electro-polymerization. The HEMA-PLA coating was chemically characterized. Mechanical performance during stent expansion was tested. Morphology examinations showed a strong adhesion of PLA topcoat in the presence of the electrografted layer. Biocompatibility and degradation of the coating were studied in vitro and in vivo in rabbit iliac arteries. These 28 days implantations resulted in a minimal inflammatory process with a partial degradation of the coating. These results suggest that this kind of anchoring of a biodegradable layer shows great potential for drug-eluting stents.     

Modeling optimizes PEM fuel cell performance using three-dimensional multi-phase computational fluid dynamics model

This paper presents the results of an optimization study using a comprehensive three-dimensional, multi-phase, non-isothermal model of a PEM fuel cell that incorporates the significant physical processes and the key parameters affecting fuel cell performance. The model accounts for both the gas and liquid phase in the same computational domain and, thus, allows for the implementation of phase change inside the gas diffusion layers. The model includes the transport of gaseous species, liquid water, protons, energy and water dissolved in the ion conducting polymer. Water is assumed to be exchanged among three phases; liquid, vapor and dissolved, and equilibrium among these phases is assumed. The model features an algorithm that allows a more realistic representation of the local activation overpotentials, which leads to improved prediction of the local current density distribution. This model also takes into account convection and diffusion of different species in the channels as well as in the porous gas diffusion layer, heat transfer in the solids as well as in the gases and electrochemical reactions. The results showed that the present multi-phase model is capable of identifying important parameters for the wetting behavior of the gas diffusion layers and can be used to identify conditions that might lead to the onset of pore plugging, which has a detrimental effect on the fuel cell performance. This model is used to study the effects of several operating, design and material parameters on fuel cell performance. Detailed analyses of the fuel cell performance under various operating conditions have been conducted and examined.     

When does a vessel become a pipe?

The conditions under which the transient outflow from a punctured pipeline may be approximated as that emanating from a vessel using a simplified analytically based vessel blowdown model (VBM) is investigated in this article. The above addresses the fundamental drawback of long computational run times associated with the numerically based techniques used for simulating pipeline puncture failures. The efficacy of the VBM is tested by comparison of its predictions against simulation data obtained using a validated rigorous but computationally demanding numerical technique based on the method of characteristics. The results show that the accuracy of the VBM increases with decreasing puncture/pipe diameter ratio, line pressure, and increasing pipeline length. Surprisingly, the VBM produces more accurate predictions for two‐phase mixtures when compared with permanent gases. This is found to be a consequence of the better applicability of the isothermal bulk fluid decompression assumption within the pipeline in the case of two‐phase mixtures. © 2011 American Institute of Chemical Engineers AIChE J, 2011     

A Biodegradable Scale Inhibitor for Oil Well Application

Abstract

Ascorbic acid, an easily biodegradable natural product with an excellent environmental profile, was studied in an oil well downhole condition for inhibiting calcium carbonate scale deposition. Scale inhibition efficiency studied in artificial seawater and formation water mixtures of various proportions through static jar test and dynamic tube blocking tests show its calcite scale inhibition potential at high-temperature wellbore conditions. Investigation made through scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and Fourier transform infrared spectrometry revealed severe structural anomalies of CaCO₃ crystals and explain the scale prevention mechanism. Its biodegradation rate studied using a UV-visible method in a marine environment is excellent and meets environment requirements. In a sensitive marine environment, ascorbic acid could be deployed as an excellent green chemical for continuous injection into the wellbore to prevent carbonate scale deposition.     

The Effect of DC Electrical Potential on Enhancing Sandstone Reservoir Permeability and Oil Recovery

Abstract

The merits of using electrokinetic phenomena to improve reservoir permeability on sandstone reservoir core plugs are investigated with detail clay mineralogy studies. Normal and reverse DC configuration is applied along with waterflood and studies are conducted on single-phase and two-phase fluid saturation conditions. The produced brines are acid digested and analyzed by inductively coupled plasma mass spectroscopy (ICP-MS). In single-phase flow experiments, permeability enhanced 180% with the normal electrode configuration but negligible change is observed in reverse configuration. In two-phase flow 59% and 10% permeability enhancement is observed in normal and reverse configurations, respectively. In addition, 11.6% additional oil is recovered from normal configuration. The results are examined in terms of electrolyte movement and resulting changes within the clay microstructure. In normal electrode configuration, formation of colloidal clay suspension and flowing out along with produced brine is evident. This has resulted in increased pore passage and core permeability, whereas in the reverse configuration, clay structures remained unchanged. The given explanations are supported by ICP-MS and X-ray diffraction results.