Sharif Digital Repository

Filtrate and solid invasion from drilling fluids are two key sources of formation damage, and can result in formation permeability impairment. Typically, spurt invasion of mud solids causes the evolution of an external mud cake which tends to reduce further solids and filtrate influx. However, uncontrolled spurt and filtrate invasion are detrimental because they reduce the permeability of the formation. Mud composition, formation rock's permeability and porosity, and temperature can influence both spurt and filtrate invasion. The sizes of mud solids relative to the average pore size of a rock are also important in predicting the extent of mud invasion and permeability impairment. In this... 

Online selection of the appropriate model and identifying its parameters based on measured vibrational data are among the challenging issues in dynamic system identification. After a severe earthquake, quick monitoring and assessment of structural health status play a crucial role in effective critical risk management for the building owners and decision-makers. The Bayesian multiple modeling approach is a suitable tool for optimal model class selection, which is used in this article mainly for improving data fitting precision, decreasing dimensions of structural unknown vector through removing unnecessary parameters, detecting the occurrence and type of predominant phenomenon related to... 

Due date assignment for customer orders has been studied in various production environments using different modeling approaches. In this paper the researchers consider a production system in which the orders of several customers are produced in a single batch because of the economy of scale. If a batch is completed before receiving customer orders, inventory carrying cost is incurred but if it is completed after receiving customer orders, shortage cost is incurred and finally if the order is delivered after its due date, tardiness cost is charged. The problem is to decide on batch size, due date of batch (imposed on supply process) and lead time (to be quoted to the next coming customers) so... 

A dc-dc resonant converter has the advantage of overcoming switching losses and electromagnetic interference which are the main limitations of high frequency power converters. Nevertheless, the modeling and stability analysis of dc-dc resonant converters are considerably more complex than pulsewidth modulation counterparts. The conventional averaged linearized model of the resonant converter has limitations due to averaging and linearization. First of all, the linearized model has large modeling error in presence of large variations of reference voltage and input voltage. Furthermore, Converging area for stabilizing controllers is smaller in the averaged model. In order to overcome these... 

The present study deals with the feasibility of a microfluidic microbial electrolysis cell (MEC) as an efficient biohydrogen generator for medical usage for the first time. The evaluation of nickel in microfluidic MEC as an alternative for conventional electrodes indicates successful performance in the improvement of bioenergy production. The maximum biohydrogen production rate and produced power density of 2.2 μW cm−2 and 1.4 μl H2 μl substrate−1 day−1 were obtained, respectively. It is considered a promising technology for medical usage due to the following factors: significant biohydrogen generation, low consumption of expensive materials, simple construction, and utilization of human... 

This paper focused on the conceptual design of a conventional gas turbine combustor via the multi-objective optimization approach. The suggested method integrated the design and estimation of the performance of the combustion chamber. The geometry and performance parameters could be found by applying the design tool. According to the level of available information in the primary phases of the design process, a chemical reactor network approach for modeling the combustion was chosen; thus, the droplet evaporation of the liquid fuel and unmixedness of the fuel-air mixture in the primary zone was modeled. The results obtained from the design tool for the two annular combustors were compared... 

The rise of the damage to energy systems caused by both natural and man-made disruptive events and the connection between energy systems and socio-economic systems have motivated the study of energy system resilience. This paper conceptualizes and comprehensively presents a systematic review of the recent literature focused on the analytical, technical, and mathematical points from the standpoint of the energy systems facing disruptive events. To this end, five phases are developed. Firstly, the concept of the energy system resilience is presented, and then the energy resilience characters and the resilience states are introduced and connected. Thirdly, the formulation and indicators of the... 

The rise of the damage to energy systems caused by both natural and man-made disruptive events and the connection between energy systems and socio-economic systems have motivated the study of energy system resilience. This paper conceptualizes and comprehensively presents a systematic review of the recent literature focused on the analytical, technical, and mathematical points from the standpoint of the energy systems facing disruptive events. To this end, five phases are developed. Firstly, the concept of the energy system resilience is presented, and then the energy resilience characters and the resilience states are introduced and connected. Thirdly, the formulation and indicators of the... 

Based on Lagrangian mechanics, we present a novel and computationally efficient set of equations of motion in the matrix notation, for unconstrained or constrained mechanical systems including ignorable coordinates. The equations are applicable to multibody systems including holonomic or nonholonomic constraints. It is shown that by appropriate selection of generalized speeds as a new set of motion variables, the constraint reaction forces can be automatically eliminated from the set of developed reduced dynamical equations in a straightforward manner, resulting in a minimal set of dynamic equations. We present simulation results on one constrained and one unconstrained system to demonstrate... 

Clay liners are widely used as porous membrane barriers to control solute transport and to prevent the leakage of leachate both in horizontal and vertical flow scenarios, such as the isolated base and ramps of sanitary landfills. Despite the primary importance of saturated hydraulic conductivity in a reliable simulation of fluid flow through clay barriers, there is no model to predict hydraulic conductivity of clayey soils permeated with saline aqueous solutions because most of the current models were developed for pure water. Therefore, the main motivation behind this study is to derive semi-empirical models for simulating the hydraulic conductivity of clayey soils in the presence of... 

Streaming potential measurement is one of the electrokinetic techniques used to determine the average zeta potential of porous rock which can provide reliable information on reservoir flow behavior and wettability state of the rock surface. Streaming potential measurement using electrodes has recently been introduced in the oil reservoirs applications and there are still significant uncertainties during the measurements and interpretation of streaming potential results. The primary purpose of this work is to establish a setup to measure the streaming potential of porous media with low scattering and evaluate voltage measurements based on the paired stabilization and pressure ramping methods.... 

This fact is well known that during any scenario of production, asphaltene deposition in porous media has a substantial effect on oil flow. But a clear understanding of asphaltene deposition mechanisms can help to minimize asphaltenic problem in oil-bearing formations. In this study, the experimental results of three dynamic CO 2 miscible injection tests were investigated. Regarding the effects of adsorption, mechanical entrapment, and sweeping mechanisms on permeability behavior, a mathematical mass and permeability variation model were developed. According to the experimental results asphaltene deposition causes a 70% loss of sand stone initial permeability while the loss is significantly... 

In this paper, we propose a new packet routing scheme, i.e., a combined digital and analog network coding scheme (DNC-ANC) suitable for multiple unicast scenario. In this respect, we consider a random access WLAN comprised of single and multi-hop unicast sessions. Then we modify the MAC scheme in order to enable ANC. In order to evaluate the effect of the proposed DNC-ANC scheme analytically, we employ an open queueing network and map the details of MAC as well as routing schemes onto its suitable parameters. By writing the corresponding traffic equations and applying the stability condition, we are able to find the maximum stable throughput for the considered scenario. Finally, we will show... 

Wind power is a promising source of electric power generation since it has tremendous environmental and social benefits. The generation scheduling (GS) problem encounters several uncertainties in terms of the system's parameters such as load, reserve and available wind power generation. The modeling of those uncertainties is an important issue in power system scheduling. A fuzzy based modeling approach can be used to develop the generation schedule under an uncertain environment. In this paper, the type-2 fuzzy membership function (MF) is implemented to model the linguistic uncertainty of type-1 MF of available wind power generation which stems from opinions of different experts. The... 

Gas turbine has broad applications in variety of industries. The developing gas turbine efficiency is of great engineering concern. This appeals to more precise modeling as somewhat inevitable. Modeling plays a decisive and essential role not only in all design phases, but also in development and manufacturing process to investigate performance of an engine. In this research, components of a gas turbine including air intake, axial and centrifugal compressors, combustion chamber and axial turbine are investigated. A novel dimensionless modeling approach is introduced and then, the engine performance parameters are predicted. Setting up a systematic series of experiments on the existing engine... 

The strengthening behavior of particle reinforced metal-matrix composites is primarily attributed to the dislocation strengthening effect and the load transfer effect. To account for these two effects in a unified way, a new multi-scale approach is developed in this paper incorporating the aspect ratio effect into the geometrically necessary dislocation strengthening relationships. By making use of this multi-scale approach, the deformation behavior of metal-matrix composites (MMCs) and metal-matrix nanocomposites (MMNCs) as a function of size, volume fraction, aspect ratio, etc. of the particles has been investigated. Comparison with the previously proposed models and the available... 

Needle insertion simulation and planning systems (SPSs) will play an important role in diminishing inappropriate insertions into soft tissues and resultant complications. Difficulties in SPS development are due in large part to the computational requirements of the extensive calculations in finite element (FE) models of tissue. For clinical feasibility, the computational speed of SPSs must be improved. At the same time, a realistic model of tissue properties that reflects large and velocity-dependent deformations must be employed. The purpose of this study is to address the aforementioned difficulties by presenting a cost-effective SPS platform for needle insertions into the liver. The study... 

This paper presents a hybrid adaptive network based fuzzy inference system (ANFIS), computer simulation and time series algorithm to estimate and predict electricity consumption estimation. The difficulty with electricity consumption estimation modeling approach such as time series is the reason for proposing the hybrid approach of this study. The algorithm is ideal for uncertain, ambiguous and complex estimation and forecasting. Computer simulation is developed to generate random variables for monthly electricity consumption. Various structures of ANFIS are examined and the preferred model is selected for estimation by the proposed algorithm. Finally, the preferred ANFIS and time series... 

The paper presents further experiments with an extended version of a comprehensive model for assessment of energy technologies and research and development (R&D) planning to evaluate the impact of innovation programs on development of Iranian electricity-supply system. This analytical instrument is a model of energy R&D resource allocation with an explicit perspective of developing countries which has been linked to a bottom-up energy-systems model. Three emerging electricity generation technologies of solar PV, wind turbine and gas fuel cell are considered in the model and the impact of innovation programs on cost-reducing innovation for them is examined. The main results provided by the...