Sharif Digital Repository

A new polymer gel nanocomposite is fabricated for excess water production control (water shut off) in petroleum reservoirs and its rheological behavior is evaluated in the presence of sea water and formation water at the temperature of 100 °C. It is shown that at a high salinity without using SiO2 nanoparticles, the elastic modulus of synthesized polymer gel in the presence of sea water and formation water are 12.5 Pa and 9.8 Pa respectively. However by incorporation of SiO2 nanoparticles in the polymer gel matrix, the elastic modulus of synthesized polymer gel in the presence of sea water and formation water can be improved to 13.56 Pa and 11.57 Pa respectively, which is quite interesting... 

A new polymer gel nanocomposite is fabricated for excess water production control (water shut off) in petroleum reservoirs and its rheological behavior is evaluated in the presence of sea water and formation water at the temperature of 100 °C. It is shown that at a high salinity without using SiO2 nanoparticles, the elastic modulus of synthesized polymer gel in the presence of sea water and formation water are 12.5 Pa and 9.8 Pa respectively. However by incorporation of SiO2 nanoparticles in the polymer gel matrix, the elastic modulus of synthesized polymer gel in the presence of sea water and formation water can be improved to 13.56 Pa and 11.57 Pa respectively, which is quite interesting... 

A new nanocomposite polymer gel is synthesized for reduction of excess water production in petroleum reservoirs at real operating conditions. This new nanocomposite gel contains SiO2 nanoparticles, partially hydrolyzed polyacrylamide (HPAM) and chromium triacetate. High pressure and high temperature tests using porous carbonate core are carried out to evaluate the effects of nanoparticles on the synthesized polymer gel performance. It is shown that the residual resistance factor ratio of water to oil using the synthesized polymer gel nanocomposite in this work is much higher than that of the ordinary polymer gels. The presented results confirm the high performance of the synthesized... 

Reconfigurability in software has many advantages such as updating, bug fixing and adding new services. Dynamic reconfiguration is more useful for mission critical systems that need to change in run time. Reconfiguration of a system in network may result to reconfiguring its dependent systems, which we call reconfiguration propagation. In this paper, we present a model for reconfiguration propagation for systems in a network  

Hot deformation behavior of Al6063 alloy produced by direct powder extrusion was studied by means of uniaxial compression test in the temperature range between 300 and 450°C and strain rate range between 0.01 and 1s -1. Electron backscatter diffraction (EBSD) technique and transmission electron microscopy (TEM) were utilized to study the microstructure of the material before and after the hot deformation. The microstructure of the extruded alloy consisted of elongated grains within a subgrain structure and small grains free of low angle grain boundaries (LAGBs). An equiaxed duplex microstructure consisting of large substructured grains and fine grains separated by high angle grain boundaries... 

Uniaxial compression test at different temperatures [573 K to 723 K (300 °C to 450 °C)] and strain rates (0.01 to 1 s−1) was employed to study the hot deformation behavior of an ultrafine-grained (UFG) Al6063 alloy prepared by the powder metallurgy route. The UFG alloy with an average grain size of ~0.3 µm was prepared by mechanical milling of a gas-atomized aluminum alloy powder for 20 hours followed by hot powder extrusion at 723 K (450 °C). To elaborate the effect of grain size, the aluminum alloy powder was extruded without mechanical milling to attain a coarse-grained (CG) structure with an average grain size of about 2.2 µm. By employing the dynamic materials model, processing maps for... 

Compression test was used to study the deformation behaviour of sintered (12% porosity) and powder extruded (1% porosity) Al6061 alloy at high temperatures ranging from 350 to 500°C. The flow curves of the materials were determined at strain rates of 0.001, 0.01 and 0.1 s-1. The extruded alloy exhibited plastic instability in the form of bulging and formation of shear bands. The deformation activation energy of the extruded material was determined to be QI=77±16 kJ mol-1 (T<450°C) and OII=136±12 kJ mol-1 (T≥450°C). The values of activation energy and appearance of strain softening in the stress-strain curves revealed that thermally activated restoration processes, i.e. dynamic recovery and... 

In this paper, we propose a Gaussian Process Regression (GPR) framework for concealment of corrupted motion vectors in predictive video coding of packet video systems. The problem of estimating the lost motion vectors is modelled as a kernel construction problem in a Bayesian framework. First, to describe the similarity between the neighboring motion vectors, a kernel function is defined. Then the parameters of the kernel function is estimated as the coefficients of a linear Bayesian estimator. The experimental results verify the superiority of the proposed algorithm over the conventional and state of the art motion vector concealment methods. Moreover, noticeable improvements on both... 

The main purpose of this paper is modeling and simulation of in-situ releasing of smart nano-sized core-shell particles at the water-oil interface during polymer flooding. During the polymer flooding process, when these nano-particles reach the water-oil interface, migrate to the oil phase and the hydrophobic layer of them dissolves in this phase. After dissolution of this protective nano-sized layer, the hydrophilic core containing a water-soluble ultra high molecular weight polymer diffuses back into the water phase and with dissolving in this phase, dramatically increases viscosity of flooding water in the neighborhood of the water-oil interface. In this study, two different... 

The effects of geometrical scaling on a supersonic external compression axisymmetric inlet are investigated. Various lower and higher geometrical scales of supersonic inlet are considered as the case studies. The inlet flow is simulated numerically using RANS solver along with the SST k-w turbulence model. The numerical results are in an acceptable agreement with the NACA experimental data at free stream Mach number of 1.79 and at zero angle of attack. The results show that the static pressure distribution of the inlet flow experiences some differences for various scales especially at the regions of the flow entrance and throat area. The mean flow Mach number and the mass flow rate at the... 

The S-shaped air intakes are very common shapes due to their ease in the engine-body integration or Radar Cross Section, RCS, specifications especially for fighter aircrafts. The numerical shape optimization of an S-shaped air intake using adjoint method is conducted. The flow of a specified air intake that uses S-duct M2129 is simulated using three dimensional (3D) numerical solution of Reynolds-Averaged Navier-Stokes equation along with k-ω SST turbulence model. The main purpose of this optimization scheme is to maximize the total pressure recovery (TPR). Further, the scheme is developed in such a way that would be applicable in industry thru satisfying specified constraint requirements.... 

We have investigated hydrogen sensing properties of electrodeposited Pd clusters on macroporous silicon substrates. Porous layer was prepared by electrochemical etching of p-type silicon (100) wafer in organic electrolyte DMF (dimethylformamide) diluted by HF (%95 Vol. %). The deposition of Pd was carried out by linear voltammetry (LV) technique. This technique was taken for reduction of palladium ions in the potential range from 0.4 V to -1 V vs. SCE, at the scan rate of 20 mV s-1. Some samples were annealed at 300°C for an hour in air to study the effect of heat treatment on their gas sensitivity. Surface structural and chemical properties of the samples were characterised using Scanning... 

Enhanced Oil Recovery techniques are gaining more attention worldwide as the proved oil reserves are declining and the oil price is hiking. Although many giant oil reservoirs in the world were already screened for EOR processes, the main challenges such as low sweep efficiency, costly techniques, possible formation damages, transportation of huge amounts of EOR agents to the fields especially for offshore cases, analyzing micro-scale multi-phase flow in the rock to the large scale tests and the lack of analyzing tools in traditional experimental works, hinder the proposed EOR processes. Our past experiences on using nanotechnology to the upstream cases, especially EOR processes, revealed... 

We propose to use a compressed sensing recovery method called IMATCS for improving the resolution in microwave imaging applications. The electromagnetic inverse scattering problem is solved using the Distorted Born Iterative Method combined with the IMATCS algorithm. This method manages to recover small targets in cases where traditional DBIM approaches fail. Furthermore, by applying an L2-based approach to regularize the sparse recovery algorithm, we improve the algorithm's robustness and demonstrate its ability to image complex breast structures. Although our simulation scenarios do not fully represent experimental or clinical data, our results suggest that the proposed algorithm may be... 

Progressive image transmission enables the receivers to reconstruct a transmitted image at various bit rates. Most of the works in this field are based on the conventional Shannon-Nyquist sampling theory. In the present work, progressive image transmission is investigated using sparse recovery of random samples. The sparse recovery methods such as Iterative Method with Adaptive Thresholding (IMAT) and Iterative IKMAX Thresholding (IKMAX) are exploited in this framework since they have the ability for successive reconstruction. The simulation results indicate that the proposed method performs well in progressive recovery. The IKMAX has better final reconstruction than IMAT at the cost of... 

We propose a new image recovery method to improve the resolution in microwave imaging applications. Scattered field data obtained from a simplified breast model with closely located targets is used to formulate an electromagnetic inverse scattering problem, which is then solved using the Distorted Born Iterative Method (DBIM). At each iteration of the DBIM method, an underdetermined set of linear equations is solved using our proposed sparse recovery algorithm, IMATCS. Our results demonstrate the ability of the proposed method to recover small targets in cases where traditional DBIM approaches fail. Furthermore, in order to regularize the sparse recovery algorithm, we propose a novel... 

In this paper, we present a compressive sampling and multihypothesis (MH) reconstruction strategy for video sequences that has a rather simple encoder, while the decoding system is not that complex. We introduce a convex cost function that incorporates the MH technique with the sparsity constraint and the Tikhonov regularization. Consequently, we derive a new iterative algorithm based on these criteria. This algorithm surpasses its counterparts (Elasticnet and Tikhonov) in recovery performance. Besides, it is computationally much faster than Elasticnet and comparable with Tikhonov. Our extensive simulation results confirm these claims  

Sparse signal processing has found various applications in different research areas where the sparsity of the signal of interest plays a significant role in addressing their ill-posedness. In this invited paper, we give a brief review of a number of such applications in inverse scattering of microwave medical imaging, compressed video sensing, and missing sample recovery based on sparsity. Moreover, some of our recent results on these areas have been reported which confirms the fact that leveraging the sparsity prior of the underlying signal can improve different processing tasks in various problems. © 2016 IEEE  

In this paper, we propose a scheme referred to as integer-forcing message recovering (IFMR) to enable receivers to recover their desirable messages in interference channels. Compared to the state-of-the-art integer-forcing linear receiver (IFLR), our proposed IFMR approach needs to decode considerably less number of messages. In our method, each receiver recovers independent linear integer combinations of the desirable messages each from two independent equations. We propose an efficient polynomial-time algorithm to sequentially find the equations and integer combinations with maximum rates and analyze its complexity. We evaluate the performance of our scheme and compare the results with the... 

In this work, the vapour extraction (VAPEX) process is studied experimentally in a rectangular physical model at moderate-high pressure. The solvent was either pure propane or a mixture of propane/ methane with different compositions. The solvent and carrier gas were totally mixed before injection, so that a solvent with the desired composition flowed through the injector during experiments, and the solvent mixture was in thermodynamic equilibrium before injection into VAPEX cell. Effects of pressure and composition of solvent were studied. Results showed that at a fixed pressure, the process is more effective with pure solvent compared to the use of solvent mixtures. The main feature of...