Sharif Digital Repository

Spontaneous water imbibition into the matrix blocks is known as the main mechanism for increased oil recovery from naturally fractured oil reservoirs. The rate of oil recovery and its ultimate value is mostly affected by wettability of the rocks and their pore structure. Oil viscosity also greatly influences the rate of oil recovery. A novel experimental model was utilized to study the imbibition mechanism under different wettability conditions. Matrix blocks made from different grain types and size distributions of glass beads were saturated with two different types of synthetic oil, to mimic the oil-saturated matrixes. The wetting characteristic of the models used in this study were... 

Over the last few years, the universal number of legged robots has increased astonishingly in outdoor environments. In this paper, the design, and control of a new RHex robot named IRHex with innovative Fiberglass-Fiber carbon composite legs are described. IRHex is a six-legged robot-one actuator located at each hip-achieving mechanical uncomplicatedness that provides a reliable performance. In this investigation, the new material used for building IRHex legs was discovered after several tests on the effect of sequence and orientation of laminates in the composite. IRHex achieves robust locomotion using a computer board analyzing the data sent by the sensors and communicating to the ground... 

The HIGHT algorithm is a 64-bit block cipher with 128-bit key length, at CHES'06 as a lightweight cryptographic algorithm. In this paper, a new related-key impossible differential attack on the full-round algorithm is introduced. Our cryptanalysis requires time complexity of 2127.276 HIGHT evaluations which is slightly faster than exhaustive search attack. This is the first related-key impossible differential cryptanalysis on the full-round HIGHT block cipher. Copyright  

Municipal wastewater treatment facilities produce a lot of sludge which is concentrated with different pollutants. The sustainable design of the sludge disposal alternatives is of crucial importance for touristic cities like Mashhad in Iran. Increasing sludge generation and its accumulation in the city and more stringent legislations highlight the challenge of sludge disposal, recently. This study compares different alternatives to reach maximum possible environmental benefits as well as the most cost-effective technologies. In this study, life cycle analysis (LCA) assesses different scenarios for disposal of sewage sludge which is aerobically treated and dewatered for two real case studies.... 

Because of corrosion resistance and antibacterial effects, shape memory Ni-Ti-Ag alloy can be considered for different biomedical applications. Mechanical alloying is used to produce nanostructured Ni-Ti-Ag alloy from elemental powders. X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) are used to characterize the product. Results show that after 1h milling, homogenous distribution of the elements occurs; while no intermetallic compounds is observed. After 3h milling, titanium dissolves in nickel to form amorphous and nanostructured solid phases. Peaks of B2 phase appear in the XRD pattern after the 3h milling of the powder mixture. Sintering of the 3h-milled... 

Diversion in heterogeneous carbonate reservoirs plays the most important role to the success of acidizing. Without the use of diversion, more acid preferentially flows into the high-permeability region and leaves the low-permeability region underreacted. But a clear understanding of diverting agents, such as polymer-based in-situ-gelled acids, can help uniformly stimulate the near-wellbore region. In this paper, we correct the rheological model that was developed by Ratnakar et al. (2013) according to experimental data from Gomaa and Nasr-El-Din (2010b) by considering shear-rate effect in a two-scale continuum model. It is found that the rheology parameters and shear rate are influential... 

In this paper, a mobile manipulator is developed and studied in order to manipulate the complicated objects and navigate in an indoor environment. The arm consists of an actuator that makes the first linkage to move in two degrees of freedom in the first step of the task. In the next mode of the task, another actuator causes the second linkage to move in the third degree of freedom. In addition, the arm contains a gripper that grabs a variety of objects such as a screw. Therefore, the robotic arm can manipulate objects, and the mobile robot connected to the arm can detect, classify and track targets in its surrounding. Results carried out that the manufactured robot is able to manipulate and... 

In this study, an equiatomic mixture of Ni and Ti powders has been mechanically milled for 180 h in a planetary mill in order to study the product phase of milling process. Miedema's semi empirical method has been used in order to calculate the energy of solid solution and amorphous phases and the effect of defects like dislocations and grain boundaries have been considered in this thermodynamic approach. The results showed that amorphous phase is more stable than solid solution after mechanical milling process. It seems these results are in contrast with Mousavi et al. [1] results but there are some points that we should consider in this approach. Applying of common tangent rule and... 

This paper deals with blind separation of finite alphabet sources where we have n sources and only one observation. The method is applied directly in time (spatial) domain and no transformation is needed. It follows a two stage procedure. In the first stage the mixing coefficients are estimated, and in the second stage the sources are separated using the estimated mixing coefficients. We also study restrictions of this method and conditions for which its performance is acceptable. Simulation results are presented to show the ability of this method to source separation in images and pulse amplitude modulation (PAM) signals  

Displacement experiments of the gas-oil system are performed on long core scale models by varying the petrophysical properties and flowing conditions. Experiments are conducted in situations where capillary, gravity and viscous forces are comparable. From oil production history and picture analysis, the threshold for the stability is determined. The experimental findings are comparable to the results of a gradient percolation theory. The effect of destabilized front velocity on relative permeability and residual saturation is investigated. The relative permeabilities determined by using analytical and numerical approaches indicate that higher displacement velocity leads to a higher gas... 

In some systems with hysteresis behavior like Shape Memory Alloy (SMA) actuators and Piezo actuators, we essentially need an accurate modeling of hysteresis either for controller design or performance evaluation. One of the most interesting Hysteresis non-linearity identification methods is Preisach model in which hysteresis is modeled by linear combination of elemental operators. Despite good ability of Preisach modeling to extract main features of system with hysteresis behavior, cause of tough numerical nature of Preisach, it is not convenient to use in real-time control applications. In this paper we present a novel method based on Artificial Neural Network. For evaluation of proposed... 

One way to reduce vehicles' fuel consumption (FC) is to optimize different parts of its powertrain. Among different modern powertrains, continuously variable transmission (CVT) is one of the common types which changes speed ratio between engine and wheels, continuously. Therefore, the CVT allows the engine to operate at its fuel-optimal speed. Due to the limited power transmission capacity and speed ratio range of the CVT, researchers attempted to combine the CVT with a planetary gear train and a fixed ratio mechanism. This mechanism is called infinitely variable transmission (IVT). In this study, a multi-speed gearbox (MSG) is used in the IVT and its impact on the powertrain performance and... 

In this study, the Polyaniline/Polyvinyl Alcohol (PANi/PVA) composite was examined for arsenite (As(III)) removal from aqueous solution. The effect of several parameters including PVA concetration (0–5 g/L), pH (1–13), adsorbent dosage (0.5–6 g/L), contact time (0–120 min), initial As(III) concentration (0.5–100 mg/L), and As(III) oxidation were evaluated on the adsorption efficiency. The results indicated that PVA has an effective role in increasing adsorptive capacity of PANi, by changing its morphology and extending its active surface sites. The adsorption process was pH dependent and As(III) removal consistently improved by increasing solution pH. Adsorption reached equilibrium within... 

Recently, cloud computing infrastructure (CCI) models have received much attention for their exceptional scalability, dependability, Data Information Sharing (DIS), and low cost rate. There are many hardware and software elements that are accessed over the internet by cloud data centers. Modern data centers utilize Virtualization Techniques (VT) to offer a dispersed CI that employs Virtual Machines (VM) based on Physical Hosts (PH). With the increasing number of centers, optimizing energy consumption has become vital to saving costs due to DCC's high energy consumption. In our CPS algorithm, we combine the Cuckoo algorithm and the particle swarm optimization (PSO). It is determined which... 

In this paper a novel fuzzy approach exploiting Active Learning Method is employed in order to estimate the immeasurable states required to control a non-observable double inverted pendulum. Active Learning Method (ALM) is a fuzzy modeling method which exploits Ink Drop Spread (IDS) as its main engine. IDS is a universal fuzzy modeling technique which is very similar to the way human brain processes different phenomena. The ALM system is trained by the data obtained from Linear Quadratic Regulator (LQR) controller. LQR uses an optimal control approach which under certain conditions guarantees robustness. Instead of an expert's knowledge, the LQR controller output is used as a priori... 

The electrocatalytic oxidation of methanol was studied over Ni, Co and Cu binary or ternary alloys on graphite electrodes in a NaOH solution (0.1 mol/L). The catalysts were prepared by cycling the graphite electrode in solutions containing Ni, Cu and Co ions at cathodic potentials. The synergistic effects and catalytic activity of the modified electrodes were investigated by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). It was found that, in the presence of methanol, the modified Ni-based ternary alloy electrode (G/NiCuCo) exhibited a significantly higher response for methanol oxidation compared to the other samples. The anodic peak... 

In recent years, controlling the salinity and composition of the injected water has become an emerging enhanced oil recovery (EOR) technique, often described as low salinity (LS) waterflooding. This work is done with the intention to contribute to the ongoing discussions about LS waterflooding mechanism(s). For this purpose, a series of different experiments were conducted. At first, the effect of salinity on the interfacial tension (IFT) and the contact angle was evaluated with a crude oil sample. Then to achieve more accurate results in observing oil/water interface, similar IFT experiments were also carried out on a synthetic oil containing asphaltenes. Thereafter, microscopic... 

Global issues arising from water and electricity shortages have notoriously affected social life over the last decades. In this regard, using renewable energy sources like waste heat of wind turbines (WTs) to drive desalination systems can be a promising solution. However, high specific work consumption (SWC) for desalinating seawater from the waste heat of the wind turbine generator can hinder the application of this new emerging technology. To address this problem, a multi-effect distillation mechanical-vapor compression (MED-MVC) desalination unit is used to recover the brine rejected from a humidification-dehumidification (HDH) desalination unit operating by the waste heat of the... 

In this study, the performance of an aerobic moving bed biofilm reactor (MBBR) was assessed for the removal of phenol as the sole substrate from saline wastewater. The effect of several parameters namely inlet phenol concentration (200-1200 mg/L), hydraulic retention time (8-24 h), inlet salt content (10-70 g/L), phenol shock loading, hydraulic shock loading and salt shock loading on the performance of the 10 L MBBR inoculated with a mixed culture of active biomass gradually acclimated to phenol and salt were evaluated in terms of phenol and chemical oxygen demand (COD) removal efficiencies. The results indicated that phenol and COD removal efficiencies are affected by HRT, phenol and salt... 

This paper studies unamped oscillations of fractional-order Duffing system. Stability theorems for fractional order systems are used to determine the characteristic polynomial of the system in order to find the parametric ranges for undamped oscillations in this system. We also derive relations for estimating the frequency and the amplitude of the oscillations in this system using a describing function method. Finally numerical simulation results are provided to justify the analysis