Sharif Digital Repository

One of the most important production issues in oil fields is high water production which may lead to wells killing and reduction in an economical production period. With the increment of water production or decrease of reservoir pressure, reservoir drawdown pressure reduces which causes reduction in oil production rate. To preserve the reservoir production, we should apply one of the proposed methods; namely, increasing the reservoir pressure, preventing water source invasion or using artificial lift technique. To compensate this reduction, continuous gas injection into the wells can be used. The injected gas combines with fluid in tubing and the density of the fluid decreases, thereby... 

Three-dimensional graphenic adsorbents have been successfully synthesized by hydrothermal reduction and applied for deep removal of dibenzothiophene (DBT) from model fuel. The nanoporous spongelike structure of the graphenic compounds was confirmed using various characterization techniques. Reduced graphene oxide (rGO), carbon black-graphene composite (CB-G), and nickel-impregnated graphene (Ni-G) showed adsorption capacities of 41.8, 46.9, and 43.3 mg of DBT g-1, respectively, and the DBT concentration in the model fuel was diminished to less than 10 ppm. Thermodynamic parameters for the adsorption process evidenced feasible and exothermic adsorption on rGO and CB-G with negative enthalpy... 

In this Paper, a software-based control flow checking technique called SWTES (Software-based error detection Technique using Encoded Signatures) is presented and evaluated. This technique is processor independent and can be applied to any kind of processors and microcontrollers. To implement this technique, the program is partitioned to a set of blocks and the encoded signatures are assigned during the compile time. In the run-time, the signatures are compared with the expected ones by a monitoring routine. The proposed technique is experimentally evaluated on an ATMEL MCS51 microcontroller using Software Implemented Fault Injection (SWIFI). The results show that this technique detects about... 

Today, the production of energy and electricity is one of the major concerns of mankind. Electricity generation by solar energy is considered as one of the alternatives to fossil fuels. Solar chimneys mechanism is based on a natural phenomenon. In this process the solar energy heat up the earth's surface and the surrounding air. Due to the density difference between cold air and warm air, heated air ascends and causes air circulation. In this study, mathematical modelling of solar chimney and governing equations of this system will be discussed. In order to validate the numerical results, upwind velocity in chimney has been compared with a reliable reference results. As well as, the... 

This paper concerns on experimental investigation of biopolymer/polymer flooding in fractured five-spot systems. In this study, a series of polymer injection processes were performed on five-spot glass type micromodels saturated with heavy crude oil. Seven fractured glass type micromodels were used to illustrate the effects of polymer type/concentration on oil recovery efficiency in presence of fractures with different geometrical properties (i.e., fractures orientation, length and number of fractures). Four synthetic polymers as well as a biopolymer at different levels of concentration were tested. Also a micromodel constituted from dead-end pores with various geometrical properties was... 

With the development of modern power systems, Smart Grid as the intelligent generation of electricity networks, has been faced with a tremendous attention. The Smart Grid systems are made up of fine-grained power grid measurements to achieve a high stability and reliability. In these networks, the data security and privacy issues for secure data sharing among the components of the system have emerged as the basic requirement. Typically, a service provider securely shares the data/commands with the smart meters under an arbitrary policy which is determined by the service providers. As the smart grid components are considered to have constrained computational resources, we cannot directly use... 

Nowadays, distributed embedded systems are employed in many safety-critical applications such as X-by-Wire. These systems are composed of several nodes interconnected by a network. Studies show that a transient fault in the communication controller of a network node can lead to errors in the fault site node (called original errors) and/or in the neighbor nodes (called follow-up errors). The communication controller of a network node can be halted due to an error, which may be a follow-up error. In this situation, a follow-up error leads to halt the correct operation of a fault-free controller while the fault site node, i.e. the faulty controller, still continues its operation. In this paper,... 

FlexRay communication protocol is expected to become the de-facto standard for distributed safety-critical systems. This paper classifies the effects of transient single bit-flip fault injections into the FlexRay communication controller. In this protocol, when an injected fault is activated, this may result in one or more error types, i.e.: Boundary violation, Conflict, Content, Freeze, Synchronization, Syntax, and Invalid frame. To study the activated faults, a FlexRay bus network, composed of four nodes, was modeled by Verilog HDL; and a total of 135,600 transient faults was injected in only one node, called the target node. The results show that only 9,342 of the faults (about 6.9%) were... 

It is now widely believed that FlexRay communication protocol will become the de-facto standard for distributed safety-critical automotive systems. In this paper, the fault sensitivity of the FlexRay communication controller registers are investigated using transient single bit-flip fault injection. To do this, a FlexRay bus network, composed of four nodes, was modeled. A total of 135,600 transient single bit-flip faults were injected to all 408 accessible single-bit and multiple-bit registers of the communication controller in one node. The results showed that among all 408 accessible registers, 30 registers were immediately affected by the injected faults. The results also showed that... 

In this paper, we consider a code-shifted reference (CSR) for the previously introduced internally coded time hopping UWB communication systems in order to avoid channel estimation. We evaluate the performance of our proposed scheme and compare the results with those of the uncoded coded-shifted reference (CSR) UWB system. Our numerical results show the substantial performance improvement when using the proposed scheme compared to the uncoded CSR system. ©2008 IEEE  

Background: Nutrigenomic has revolutionized our understanding of nutrition. As plants make up a noticeable part of our diet, in the present study we chose microRNAs of edible plants and investigated if they can perfectly match human genes, indicating potential regulatory functionalities. Methods: miRNAs were obtained using the PNRD database. Edible plants were separated and microRNAs in common in at least four of them entered our analysis. Using vmatchPattern, these 64 miRNAs went through four steps of refinement to improve target prediction: Alignment with the whole genome (2581 results), filtered for those in gene regions (1371 results), filtered for exon regions (66 results) and finally... 

As efficiency of PV modules decreases with temperature rise, cooling methods can increase the power output and efficiency. One of the strategies for this purpose is passive cooling by implementing fins to the backside of a module. In the present study, annual energy output of a 50 W panel is analytically calculated in two unfinned and pin-finned cases based on hourly meteorological data for Shiraz, Iran. The results show that with the installation of 2-cm, 4-cm and 6-cm aluminum pin fins with finned-to-total-backside-area ratios of 0.17, 0.27 and 0.55, the power output increases by 1.24–4.16%, compared to the unfinned case. This increase is equivalent to 1.04–3.50 kWh more electrical energy... 

Alkaline-Surfactant-Polymer flooding is one of the most novel chemical enhanced oil recovery methods in the petroleum industry. This method has attracted interest due to its remarkable advantages. In this work, a series of ASP floods are conducted on fractured/non-fractured carbonate rocks. The performance of the tests was investigated by various ASP floods consisting of five types of polymers, two surfactants and one common alkaline. ASP was flooded simultaneously and sequentially in four defined scenarios after water flooding. The results showed that although using hydrolysed polymers increases the recovery factor in the fractured medium, sulfonated polymers increase oil recovery even more... 

We report a new method of growing Mn-doped CdS (CdS:Mn) nanoparticles in an aqueous solution at boiling temperature. The idea is to use precursors that react only at high temperature, in order to gain crystalline luminescent nanoparticles. CdSO4, Mn(NO3)2 and Na 2S2O3 were used as the precursors, and thioglycerol was employed as the capping agent and also the reaction catalyst. Na2S2O3 is thermally sensitive and it releases S2- ions upon heating. The CdS:Mn nanoparticles obtained are about 4 nm in size and show both cubic and hexagonal crystalline phases with a ratio of 35% to 65%. The luminescence of nanoparticles contains a peak at 580 nm, which is related to Mn2+ ions. Prolonged reaction... 

CdS nanoparticles were grown using CdSO4 and Na 2S2O3 as the precursors and thioglycerol (TG) as the capping agent. TG was shown to exhibit a catalytic role in the reaction and also acted as a capping agent. It was demonstrated that size growth is linearly related to the temperature of the reaction, i.e.the sizes can be controllably adjusted by temperature. The crystalline phase of the nanocrystals was also dependent on the temperature of growth: higher temperature favours the cubic phase. The pH also plays an important role in nanoparticle growth, as lower pH leads to a higher release rate of sulfur species. At pH as high as 10, the growth rate remains slow even at boiling temperature. This... 

Although Alkaline-Surfactant-Polymer (ASP) flooding is proved to be efficient for heavy oil recovery, the displacement mechanisms/efficiency of this process should be discussed further in fractured porous media especially in typical waterflood geometrical configurations such as five-spot injection-production pattern. In this study, several ASP flooding tests were conducted in fractured glass-etched micromodels which were initially saturated with heavy oil. The ASP flooding tests were conducted at constant injection flow rates and different fracture geometrical characteristics were used. The ASP solutions constituted of five polymers, two surfactants and three alkaline types. The results... 

Although alkaline-surfactant-polymer (ASP) flooding has proven efficient for heavy oil recovery, the displacement mechanisms and efficiency of this process should be discussed further in fractured porous media. In this study, several ASP flooding tests were conducted in fractured glass-etched micromodels with a typical waterflood geometrical configuration, i.e. five-spot injection-production pattern. The ASP flooding tests were conducted at constant injection flow rates but different fracture geometrical characteristics. The ASP solutions consisted of five polymers, two surfactants, and three alkaline types. It was found that using synthetic polymers, especially hydrolyzed polyacrylamide... 

Although alkaline-surfactant-polymer flooding is proved to be efficient for oil recovery from heavy oil reservoirs, the displacements mechanism/efficiency of this process in fractured systems needs to more discussion, especially in five-spot patterns. In this work, several ASP flooding test were performed on fractured micromodels which were initially saturated with heavy oil at constant flow rate and different fracture geometrical characteristics conditions. The ASP solutions are constituted from 5 polymers i.e. four synthetic polymers include three hydrolyzed polyacrylamide with different molecular weight as well as a non-hydrolyzed polyacrylamide and a biopolymer, 2 surfactants i.e. a... 

Microscopic and macroscopic displacements of polymer flooding to heavy oil at various levels of salinity and connate water saturation have been investigated. Both oil-wet and water-wet conditions in fractured five-spot micromodel systems, initially saturated with the heavy crude oil are utilized. The primary contribution is to examine the role of salinity, wettability, connate water, and fracture geometry in the recovery efficiency of the system. The microscopic results revealed that the increase in the connate water saturation decreases the oil recovery, independent of the wettability conditions. Moreover, the increase in salinity of the injected fluids lowers the recovery efficiency due to... 

This paper studies detecting matrices in random dense and sparse Code Division Multiple Access (CDMA) systems. Detecting matrices were originally introduced in the coin weighing problem. Such matrices can be used in CDMA systems in over-loaded scheme where the number of users is greater than the number of chips. We drive some conditions in the large system limit for binary and bipolar random CDMA systems to ensure that any random matrix is a detecting matrix. Furthermore, we extend our results to sparse random ternary matrices that have been using in the sparse CDMA literature. Finally, a construction method for the sparse detecting matrices is introduced