Sharif Digital Repository

Scale formation is one of the major problems in oilfields. Removal of scales is a difficult process due to their relative hardness and low solubility. Therefore it is valuable to find a method which can remove damages caused by scales. Ultrasonic radiation is known have the sufficient energy to remove the scales. Our purpose is to investigate the role of ultrasound on permeability increments due to scale removal. Some experiments were carried out to find these effects and observed that ultrasound has increased volumetric mass transfer, concentration and solubility limits. We also worked on a model presented by Tahmasebi et. al[2010] and applied changes on it to make it able to predict... 

Many-body systems can have multiple equilibria. Though the energy of equilibria might be the same, still systems may resist to switch from an unfavored equilibrium to a favored one. In this paper we investigate occurrence of such phenomenon in economic networks. In times of crisis when governments intend to stimulate economy, a relevant question is on the proper size of stimulus bill. To address the answer, we emphasize the role of hysteresis in economic networks. In times of crises, firms and corporations cut their productions; now since their level of activity is correlated, metastable features in the network become prominent. This means that economic networks resist against the recovery... 

It has been shown that one kind of poly silicon particles with sizes ranging from 10-500 nm, can be used in oilfields to enhance the oil recovery of water injection by 15-20%. The contributing mechanism might be reducing the interfacial tension which appears through improving relative permeability of the oil-phase. However, fundamental understanding of how hysteretic behavior of relative permeability curves affected by nanosilica particles remains a topic of debate in the literature. In this study, water as well as water dispersed nanosilica particles floods was performed on sandstone rock sample saturated by light crude oil supplied from one of Iranian oil reservoir, and the relative... 

Nano-biocomposites are a new class of hybrid materials composed of nano-sized filler (nanofiller) incorporated into a bio-based matrix. Such an association between eco-friendly biopolymers and nano-objects, with the aim to obtain synergic effects, is one of the most innovating routes to enhance the properties of these bio-matrices. In recent years, there has been an increasing interest in Starch as an inexpensive and renewable source has been used as a filler for environmentally friendly plastics for about two decades. However, the poor mechanical properties of starch based biopolymers, leads to use of nanoparticles as reinforcing materials. In the present study, the influence of a... 

It has been shown that one kind of poly silicon particles with sizes ranging from 10-500 nm, can be used in oilfields to enhance the oil recovery of water injection by 15-20%. The contributing mechanism might be reducing the interfacial tension which appears through improving relative permeability of the oil-phase. However, fundamental understanding of how hysteretic behavior of relative permeability curves affected by nanosilica particles remains a topic of debate in the literature. In this study, water as well as water dispersed nanosilica particles floods was performed on sandstone rock sample saturated by light crude oil supplied from one of Iranian oil reservoir, and the relative... 

We study Hydrogen sulfide gas detection properties of pure and 1% copper oxide added WO3 thin films. The spin coated deposits on alumina substrates were annealed at 500 C for 1 hour in order to improve the crystallinity of the films. The sensitivity of pure tungsten oxide is poor even at temperatures of about 100 C but the doped samples exhibit good response to H2S gas. Our data show sensitivity of about 1500 in 10 ppm diluted gas in air at 100 C. The films are sensitive to the gas even at 250 ppb (sensitivity about 2) H2S concentration at 100 C but with rather long recovery time. Crystal structure, morphology and chemical composition of samples were studied by X-Ray diffraction (XRD),... 

Bio-batteries are environmental friendly electricity generation devices that utilize energy from biological sources, like glucose[1] [2]. It consists of an anode with digesting enzymes and a cathode comprising oxygen-reducing enzymes. Immobilizing enzymes is a considerable issue in these kinds of devices. In this article, we propose two new methods for immobilizing and shifting particles likewise enzymes used in bio-batteries towards the anode or cathode end. Our experiments illustrate how tiny particles could be trapped in the nodes of the ultrasonic standing waves and by two methods of displacing the nodes, we can transfer the particles towards a desired location. First method is based on...