Sharif Digital Repository

The problem of gyrocompassing using inertial sensors, i.e., gyros and accelerometers, is addressed. North finding, with an order of accuracy of one arc-min, is not only required for the initial alignment of inertial navigation systems, but also has a critical role to play in the guidance and navigation of ships that navigate for long periods of time. In this work, after extracting the error model of an inertial navigation system and augmenting it with the error model of inertial sensors, a processing algorithm based on the Kalman filter is designed and simulated to process the navigation system velocity error, and to estimate and correct tilt and heading errors along with gyro drifts and... 

This study aims to investigate, optimize, and simulate the dispersed phase holdup at flooding conditions for the standard physical systems in a pulsed extraction column with the disc-doughnut configuration. The interaction impacts for operational parameters (pulse intensity and organic and aqueous phase velocities) and interfacial tension (systems type) were examined using the response surface approach. A novel correlation for the dependent parameter, namely holdup at flooding based on the quadratic model, was developed with the central composition design methodology. A desirable agreement between actual data and calculated data from the proposed model was observed because of the high... 

In this study, different concentrations of ascorbic acid (50, 100 and 200 μg/mL) were added to the liquid phase of a calcium phosphate cement (CPC). The cements were immersed in simulated body fluid (SBF) for different intervals and physical, physicochemical and mechanical properties of them were evaluated. The release of added ascorbic acid from CPCs into the SBF solution was also studied. From the results, both setting time and injectability of CPC decreased by adding ascorbic acid, however the compressive strength was sharply increased before soaking in SBF solution. But, the compressive strength values of all cements (with or without ascorbic acid) soaked in SBF solution for more than 7... 

In this research, a green solid catalyst of phosphomolybdic acid (HPA) prated on Chitosan was synthesized to produce biodiesel. The prepared catalyst was characterized using Fourier Transform Infrared spectroscopy (FTIR), Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-Ray (EDX), X-ray diffraction (XRD), and XRF analyses. The catalyst was applied in microwave-assisted trans-esterification of Pomegranate oil, and the biodiesel production process was optimized by response surface methodology based on central composite design (RSM-CCD). The effect of influential reaction parameters, including time (33–142 min), catalyst weight (0.15–5.6 wt%), and methanol to oil molar... 

Nitrogen has been appeared as a competitive gas injection alternative for gas-based enhanced oil recovery (EOR) processes. Minimum miscibility pressure (MMP) is the most important parameter to successfully design N2 flooding, which is traditionally measured through time consuming, expensive and cumbersome experiments. In this communication, genetic programming (GP) and constrained multivariable search methods have been combined to create a simple correlation for accurate determination of the MMP of N2-crude oil, based on the explicit functionality of reservoir temperature as well as thermodynamic properties of crude oil and injection gas. The parameters of the developed... 

In this study, kinetics, equilibrium, and mechanisms of SDBS adsorption onto carbonate rock in presence/absence of alkaline/electrolyte, which is not well discussed in the available literature, is analyzed through batch experiments. Analysis of kinetic data showed that adsorption rate of SDBS onto carbonate is controlled by both boundary layer and intraparticle diffusion, also adsorption kinetics meets pseudo second-order model. The coefficient of kinetic model is a linear function of initial and equilibrium concentrations. The adsorption isotherm experiences four distinct regions, with a rising trend in the first regions until reaching to a maximum after which decreases slightly, as the... 

In this study, kinetics, equilibrium, and mechanisms of SDBS adsorption onto carbonate rock in presence/absence of alkaline/electrolyte, which is not well discussed in the available literature, is analyzed through batch experiments. Analysis of kinetic data showed that adsorption rate of SDBS onto carbonate is controlled by both boundary layer and intraparticle diffusion, also adsorption kinetics meets pseudo second-order model. The coefficient of kinetic model is a linear function of initial and equilibrium concentrations. The adsorption isotherm experiences four distinct regions, with a rising trend in the first regions until reaching to a maximum after which decreases slightly, as the... 

The present study aims to convert waste cooking oil (WCO) into biodiesel via phosphomolybdic acid (H3PMo12O40, PMA) supported on Clinoptilolite as a novel green acid catalyst through an electrolysis procedure. The prepared catalysts were characterized by XRD, FTIR, FESEM, EDS, Elemental map, and TEM analyses. The effect of four independent variables on biodiesel yield including methanol to oil molar ratio (6:1–14:1), catalyst weight (2–5 wt%), time (3–5 h), and voltage (15–35 V) was optimized and evaluated by the response surface methodology (RSM) employing central composite design (CCD). The maximum value of biodiesel yield was 96% under the optimal conditions, including the methanol to oil... 

Oil viscosity plays a key role in reservoir simulation and production forecasting, as well as planning thermal enhanced oil recovery methods and these make its accurate determination necessary. In this communication, the most frequently used oil viscosity correlations are evaluated using a large databank of Iranian oil reservoirs which were measured using a Rolling Ball viscometer (Ruska, series 1602). To evaluate the performance and accuracy of these correlations, statistical and graphical error analyses have been used simultaneously. Three of the most accurate correlations for each region, including dead oil viscosity, viscosity below bubble point, viscosity at bubble point and the... 

In this study, internal microstrain of an iron-resin composite produced by powder metallurgy has been calculated using the Williamson-Hall method. The effects of microstrain evolution during different processing conditions on magnetic properties such as coercive force and hysteresis loss have been investigated. The results show that there are regular and similar changes of coercivity and hysteresis loss. Both of these properties are directly dependant on the pinning effect of the internal microstrain against the movement of magnetic domain walls during magnetization process. © 2006 Elsevier B.V. All rights reserved  

Continuous improvement and extension of pervasive computing environments, in which objects have high mobility and limited computing power, implies service migration to be considered as one of the main issues. On the other hand, context-awareness which is the most distinguishable feature of pervasive computing helps better serving of users. Accordingly, migration in the presence of context-awareness is considered as the underlying of our motivation. This improves the performance of migration, which is not easily achievable through traditional migration techniques. In this paper we introduce a model to support context-aware migration besides its migration process phases and framework. Our... 

In this study, the ultrafiltration of produced water was studied using a two-stage ultrafiltration process. In the first stage, the influences of operating parameters, including transmembrane pressure, temperature, and cross-flow velocity on the amount of flux decline caused by membrane fouling, were investigated using a polymeric membrane. In order to design the experiments and optimize the experimental results, the Taguchi method was applied. L9 (33) orthogonal array for experimental planning and the smaller-the-better response category was selected to obtain optimum conditions because the lowest flux decline was our aim. Analysis of variance was used to determine the most important... 

In this study, biodiesel (FAME) was prepared using a novel heterogeneous catalyst of phosphomolybdic acid (H3PMo12O40, HPMo)/support graphene oxide (GO). The characterization of the catalyst was evaluated by SEM, EDX, Map analysis, TEM, FT-IR, and Raman analyses. The production of biodiesel from waste cooking oil (WCO) was carried out by the electrolysis method. The process of the trans-esterification reaction was optimized by applying the response surface methodology (RSM) based on the central composite design (CCD) approach. The effects of four independent variables of methanol to oil molar ratio (6–12 mol:mol), catalyst weight (0.5–1.5 wt%), time (8–24 h), and voltage (30–70 V) were... 

In the last years, an appreciable effort has been directed toward developing empirical models to link the relative permeability of gas condensate reservoirs to the interfacial tension and velocity as well as saturation. However, these models suffer from non-universality and uncertainties in setting the tuning parameters. In order to alleviate the aforesaid infirmities in this study, comprehensive modeling was carried out by employing numerous smart computer-aided algorithms including Support Vector Regression (SVR), Least Square Support Vector Machine (LSSVM), Extreme Learning Machine (ELM), Multilayer Perceptron (MLP), Group Method of Data Handling (GMDH), and Gene Expression Programming... 

In this study, biodiesel (FAME) was prepared using a novel heterogeneous catalyst of phosphomolybdic acid (H3PMo12O40, HPMo)/support graphene oxide (GO). The characterization of the catalyst was evaluated by SEM, EDX, Map analysis, TEM, FT-IR, and Raman analyses. The production of biodiesel from waste cooking oil (WCO) was carried out by the electrolysis method. The process of the trans-esterification reaction was optimized by applying the response surface methodology (RSM) based on the central composite design (CCD) approach. The effects of four independent variables of methanol to oil molar ratio (6–12 mol:mol), catalyst weight (0.5–1.5 wt%), time (8–24 h), and voltage (30–70 V) were... 

Viscosity of crude oil is a fundamental factor in simulating reservoirs, forecasting production as well as planning thermal enhanced oil recovery methods which make its accurate determination necessary. Experimental determination of reservoir oil viscosity is costly and time consuming. Hence, searching for quick and accurate determination of reservoir oil viscosity is inevitable. The objective of this study is to present a reliable, and predictive model namely, Least-Squares Support Vector Machine (LSSVM) to predict reservoir oil viscosity. To this end, three LSSVM models have been developed for prediction of reservoir oil viscosity in the three regions including, under-saturated, saturated... 

In the original publication, some parts of Fig. 7 were repeated twice. Also, the citations of Fig. 7 were given incorrectly in the text. The above mentioned are corrected as follows: 1. In the section titled, “Morphological Analysis of the Prepared Membranes”, the first sentence of second para should read, “As can be seen from Fig. 7a1, the neat PVDF membrane in the absence of PAN has a sponge like structure with small pores.” 2. In the third Para, the third sentence should read, “These finger like pores, formed under the skin layeras shown in Fig. 7b2–e2, have also been reported in a similar study.” In the section titled “Fouling Analysis”, the fifth sentence of fourth para should read, “By... 

Ultrafiltration membranes were prepared from blend of the poly(vinylidene fluoride) (PVDF) with polyacrylonitrile (PAN) via phase inversion method induced by immersion precipitation. N,N-dimethylacetamide (DMAc) and water were used as solvent and coagulant (non-solvent), respectively. The effect of blending ratio on the morphology and antifouling behavior of the prepared membranes was investigated. The performance of the membranes was evaluated by using cross flow filtration of pure water and buffered bovine serum albumin (BSA) solution as feed. Contact angle measurements indicated that the hydrophilicities of the PVDF/PAN membranes increased by increasing PAN concentration in the casting... 

Accurate prediction of the PVT properties of reservoir oil is of primary importance for improved oilfield development strategies. Experimental determination of these properties is expensive and time-consuming. Therefore, new empirical models for universal reservoir oils have been developed as a function of commonly available field data. In this communication, more than 750 experimental data series were gathered from different geographical locations worldwide. Successive linear programming and generalized reduced gradient algorithm as two constrained multivariable search methods were incorporated for modeling and expediting the process of achieving a good feasible solution. Moreover,... 

The morphology of symmetric and asymmetric membranes obtained by precipitation can be rationalized by thermodynamic and kinetic parameters. Such parameters which the former relates to thermodynamic effect and the latter controls the time of separation of the cast solution film immersing in the non-solvent bath from the glass plate were calculated as dimensionless parameters for further analysis. Phase diagram was used to consider the role of thermodynamic. The kinetic properties of the membranes could be investigated by the rate of mass transfer between solvent and non-solvent. By adding additives to the polymer solution the desire for becoming two phase and also viscosity of the solution...