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    Estimating the step-change time of the location parameter in multistage processes using MLE

    , Article Quality and Reliability Engineering International ; Volume 28, Issue 8 , 2012 , Pages 843-855 ; 07488017 (ISSN) Davoodi, M ; Niaki, S. T. A ; Sharif University of Technology
    2012
    Abstract
    In this paper, maximum likelihood step-change point estimators of the location parameter, the out-of-control sample and the out-of-control stage are developed for auto-correlated multistage processes. To do this, the multistage process and the concept of change detection are first discussed. Then, a time-series model of the process is presented. Assuming step changes in the location parameter of the process, next, the likelihood functions of different samples before and after receiving out-of-control signal from an X-bar control chart were derived under different conditions. The maximum likelihood estimators were then obtained by maximizing the likelihood functions. Finally, the accuracy and... 

    Plant-wide control of an integrated molten carbonate fuel cell plant

    , Article Journal of Electrochemical Energy Conversion and Storage ; Volume 15, Issue 2 , 21 February , 2018 ; 23816872 (ISSN) Davoodi, A. H ; Pishvaie, M. R ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2018
    Abstract
    This paper presents the design and part-load operation of a molten carbonate-micro gas turbine (MCFC/MGT) hybrid system (HS), and proposes a multiloop control strategy for the HS. A mathematical model of the system is introduced. Then, the structure of process is changed and the performance of HSs at part-load operation is studied. The novelty includes utilizing some part of the main fuel instead of auxiliary fuel in the combustion stage. The results show that the new configuration has more efficiency (about 63%). In order to keep the operating system within safe limits, variables of the control system are determined. Those controlled variables are as follows: stack temperature, fuel... 

    Biodesulfurization of dibenzothiophene by a newly isolated Rhodococcus erythropolis strain

    , Article Bioresource Technology ; Volume 101, Issue 3 , 2010 , Pages 1102-1105 ; 09608524 (ISSN) Davoodi Dehaghani, F ; Vosoughi, M ; Ziaee, A. A ; Sharif University of Technology
    2010
    Abstract
    A new dibenzothiophene (DBT) desulfurizing bacterium was isolated from oil-contaminated soils in Iran. HPLC analysis and PCR-based detection of the presence of the DBT desulfurization genes (dszA, dszB and dszC) indicate that this strain converts DBT to 2-hydroxybiphenyl (2-HBP) via the 4S pathway. The strain, identified as Rhodococcus erythropolis SHT87, can utilize DBT, dibenzothiophene sulfone, thiophene, 2-methylthiophene and dimethylsulfoxide as a sole sulfur source for growth at 30 °C. The maximum specific desulfurization activity of strain SHT87 resting cells in aqueous and biphasic organic-aqueous systems at 30 °C was determined to be 0.36 and 0.47 μmol 2-HBP min-1 (g dry cell)-1,... 

    Application of a novel acrylamide copolymer containing highly hydrophobic comonomer as filtration control and rheology modifier additive in water-based drilling mud

    , Article Journal of Petroleum Science and Engineering ; Volume 180 , 2019 , Pages 747-755 ; 09204105 (ISSN) Davoodi, S ; Ramazani S.A, A ; Soleimanian, A ; Fellah Jahromi, A ; Sharif University of Technology
    Elsevier B.V  2019
    Abstract
    Deep wells suffer from the instability and disintegration of natural polymers and other commonly used additives under high pressure and high temperature condition. As a result, serious problems such as hydraulic loss, stuck pipe, and high torque and drag are expected to take place which leads to a dramatic increase in cost and time. This study presents the functionality of a novel synthetic based acrylamide-styrene copolymer (SBASC) as a supersede additive for water-based drilling mud. First, the SBASC was synthesized using an emulsion polymerization process and its particle morphological and polymer chain structural properties were determined by Field Emission Scanning Electron Microscopy... 

    Insights into application of acorn shell powder in drilling fluid as environmentally friendly additive: filtration and rheology

    , Article International Journal of Environmental Science and Technology ; 2020 Davoodi, S ; Ramazani S. A, A ; Rukavishnikov, V ; Minaev, K ; Sharif University of Technology
    Springer  2020
    Abstract
    Conventional additives used in drilling fluid may have detrimental short- and long-term impacts on the surrounding environment. The employment of biodegradable green material in drilling fluid as alternative additives will eliminate these harmful impacts. In this study, acorn shell powder is proposed as a novel biodegradable additive for application in drilling fluid. First, the acorn shell powder was prepared and then characterized in terms of chemical structure, particle size, and morphology. The acorn shell powder, with four different concentrations, was then introduced into a water-based fluid; its functionality in the fluid system was evaluated with respect to rheological and filtration... 

    A novel field applicable mud formula with enhanced fluid loss properties in High Pressure-High temperature well condition containing pistachio shell powder

    , Article Journal of Petroleum Science and Engineering ; Volume 162 , March , 2018 , Pages 378-385 ; 09204105 (ISSN) Davoodi, S ; Ramazani Ahmad, S. A ; Jamshidi, S ; Fellah Jahromi, A ; Sharif University of Technology
    Elsevier B.V  2018
    Abstract
    Sustainable technologies are the main concerns of the 21st century modified oilfield industries. The insufficiency of conventional drilling fluid formulations with a combination of hardly degradable hazardous chemicals as additives raise the demands of field-applicable innovative and environmentally friendly methods. Pistachio Shell discards as degradable wastes, which can intellectually apply in drilling fluid formulation. The experimental oilfield investigations of utilizing pistachio shell powder prove the significant enhancement of rheological properties, reduction of fluid loss and mud cake thickness in both API (Low Pressure —Low Temperature) and High Pressure—High Temperature (HPHT)... 

    Bonded composite patch repair’s fiber VF effects on damaged Al-plates fatigue employing a multi-scale algorithm

    , Article Journal of Reinforced Plastics and Composites ; 12 July , 2020 Davoodi Moallem, M ; Barzegar, M ; Abedian, A ; Hosseini Kordkheili, S. A ; Sharif University of Technology
    SAGE Publications Ltd  2020
    Abstract
    Recently, bonded composite patch repair, because of its significant advantages over traditional methods, has been highly accepted in several industries, particularly in aerospace applications. In this paper, a multi-scale finite element algorithm is proposed to simulate crack growth of repaired plates under fatigue load by considering the effects of composite micro-scale properties. The algorithm is verified through conducting an experimental set up and the proposed model is in reasonable agreement with experiments. The influences of different fiber volume fractions (VF), number of layers and fiber orientation of composite patch on the fatigue responses of adhesively bonded patch are... 

    Bonded composite patch repair’s fiber VF effects on damaged Al-plates fatigue employing a multi-scale algorithm

    , Article Journal of Reinforced Plastics and Composites ; Volume 40, Issue 1-2 , 2021 , Pages 29-40 ; 07316844 (ISSN) Davoodi Moallem, M ; Barzegar, M ; Abedian, A ; Kordkheili, S. A. H ; Sharif University of Technology
    SAGE Publications Ltd  2021
    Abstract
    Recently, bonded composite patch repair, because of its significant advantages over traditional methods, has been highly accepted in several industries, particularly in aerospace applications. In this paper, a multi-scale finite element algorithm is proposed to simulate crack growth of repaired plates under fatigue load by considering the effects of composite micro-scale properties. The algorithm is verified through conducting an experimental set up and the proposed model is in reasonable agreement with experiments. The influences of different fiber volume fractions (VF), number of layers and fiber orientation of composite patch on the fatigue responses of adhesively bonded patch are... 

    Analytical power allocation for a full-duplex decodeand- forward relay channel

    , Article IET Communications ; Volume 7, Issue 13 , September , 2013 , Pages 1338-1347 ; 17518628 (ISSN) Emadi, M. J ; Golami Davoodi, A ; Aref, M. R ; Sharif University of Technology
    2013
    Abstract
    For a fading full-duplex decode-and-forward relay channel, the authors analytically derive optimum power allocation schemes subject to individual power constraints at the source and the relay. The authors prove that the problem is a convex optimisation problem over the feasible power set, and by proposing a systematic technique to solve min-max problems, optimum power allocations are derived in closed-forms. Finally, for a Rayleigh-fading channel model, optimum power allocations are derived and the respective achievable rate and an upper bound are evaluated. The implications of the derived theoretical results are discussed through some graphs  

    Application of sustainable saffron purple petals as an eco-friendly green additive for drilling fluids: A rheological, filtration, morphological, and corrosion inhibition study

    , Article Journal of Molecular Liquids ; Volume 315 , 2020 Ghaderi, S ; Haddadi, S. A ; Davoodi, S ; Arjmand, M ; Sharif University of Technology
    Elsevier B.V  2020
    Abstract
    In this study, effects of dried saffron purple petals (SPP) powder were examined on the rheological, fluid loss, and corrosion inhibition properties of bentonite-based drilling fluids. Drilling fluids containing different amounts of the SPP powder were prepared and their rheological behavior was investigated via the rotary viscometry and rheometric mechanical spectroscopy (RMS). Rotary viscometer results were fitted with Power-law, Bingham plastic, and Herschel-Bulkley models and the obtained data were compared with that of the base mud. All models fitted the rotary viscometer data with the determination coefficients higher than 0.93. The presence of 3 wt% of the SSP in the fluid... 

    Assessment and Performance Improvement of Hierarchical Voltage Control System

    , M.Sc. Thesis Sharif University of Technology Davoodi, Ehsan (Author) ; Parniani, Mostafa (Supervisor)
    Abstract
    Hierarchical voltage control is one of the conventional kinds of coordinated voltage control schemes which has been studied in some countries in the last decades. In this method network is divided into several voltage control regions and in each region voltage profile is controlled near optimal level, satisfying the economic and secure goals of the network performance. In this thesis, after the explanation of the main concepts of this scheme, its effects on the network voltage control is assessed and its performance is improved. First the primary concepts of hierarchical voltage control are explained. Then, the methods of the control regions determination and pilot nodes selection are... 

    Numerical Simulation of a Telescopic Metallic Yielding Damper

    , M.Sc. Thesis Sharif University of Technology Davoodi, Vahid (Author) ; Eskandari, Morteza (Supervisor)
    Abstract
    In this study, a new type of metallic yielding damper called Telescopic damper is proposed and analyzed numerically. The damper comprises of three concentric steel tubes connected together by lead shear keys. The relative axial deformation of steel tubes under axial forces results in shear deformation and yielding in lead shear keys and dissipates energy. The inner steel tube has a lock which limits its movement to some certain extent and beyond this limit the outer tube activates. Therefore, a multi-linear force-deformation behavior with two different yield plateaus is expected for the introduced telescopic damper. The multi-level yield plateaus of damper makes it effective in both low and... 

    Effect of Boundary Element Details on the Seismic Behavior of Shear Walls in Concrete Structures

    , M.Sc. Thesis Sharif University of Technology Davoodi, Ali (Author) ; Moghaddam, Hassan (Supervisor)
    Abstract
    Using shear walls as an earthquake resistant system in reinforced concrete structures enjoys prominent position among civil engineers in recent years. As most produced stress and damage occurs at the edges of shear wall under combination of vertical and lateral loads, it is expected that seismic behavior of shear walls can be improved by using boundary element at their edges and considering special reinforcing rules. In this thesis, the effect of boundary element details and parameters on seismic behavior of shear walls has been evaluated by a finite element model. By comparing the results with parameters specified in codes, the modeling parameters and performance levels given for shear... 

    Harmonic analysis of common-mode voltage in quasi-z-source inverters

    , Article 2019 IEEE International Conference on Industrial Technology, ICIT 2019, 13 February 2019 through 15 February 2019 ; Volume 2019-February , 2019 , Pages 1778-1783 ; 9781538663769 (ISBN) Noroozi, N ; Yaghoubi, M ; Davoodi, A ; Ouni, S ; Zolghadri, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Abstract
    In a transformerless grid-connected photovoltaic system, many issues arise from the leakage current flow into the ground, as EMI problems. The leakage current is originated from the common-mode voltage fluctuations. In this paper, the common-mode voltage harmonics in a three-phase quasi-Z-source inverter are analyzed using Fourier transform and a closed-loop formulation is presented for the harmonics value. The shoot-through mode in a quasi-Z-source inverter causes extra fluctuations in the common-mode voltage comparing to a classic inverter. The proposed harmonic analysis method provides a systematic way to figure out how shoot-through mode and also other parameters affect the common-mode... 

    Insights into application of acorn shell powder in drilling fluid as environmentally friendly additive: filtration and rheology

    , Article International Journal of Environmental Science and Technology ; Volume 18, Issue 4 , 2021 , Pages 835-848 ; 17351472 (ISSN) Davoodi, S ; Ramezani Saadat Abadi, A ; Rukavishnikov, V ; Minaev, K ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2021
    Abstract
    Conventional additives used in drilling fluid may have detrimental short- and long-term impacts on the surrounding environment. The employment of biodegradable green material in drilling fluid as alternative additives will eliminate these harmful impacts. In this study, acorn shell powder is proposed as a novel biodegradable additive for application in drilling fluid. First, the acorn shell powder was prepared and then characterized in terms of chemical structure, particle size, and morphology. The acorn shell powder, with four different concentrations, was then introduced into a water-based fluid; its functionality in the fluid system was evaluated with respect to rheological and filtration... 

    Estimating the change point of correlated poisson count processes

    , Article Quality Engineering ; Volume 26, Issue 2 , 2014 , Pages 182-195 ; ISSN: 08982112 Asghari Torkamani, E ; Niaki, S. T. A ; Aminnayeri, M ; Davoodi, M ; Sharif University of Technology
    2014
    Abstract
    Knowing the time of change would narrow the search to find and identify the variables disturbing a process. The knowledge of the change point can greatly aid practitioners in detecting and removing the special cause(s). Count processes with an autocorrelation structure are commonly observed in real-world applications and can often be modeled by the first-order integer-valued autoregressive (INAR) model. The most widely used marginal distribution for count processes is Poisson. In this study, change-point estimators are proposed for the parameters of correlated Poisson count processes. To do this, Newton's method is first used to approximate the parameters of the process. Then, maximum... 

    Change Point Estimation for Multistage Processes

    , Ph.D. Dissertation Sharif University of Technology Davoodi, Mehdi (Author) ; Akhavan Niaki, Taghi (Supervisor)
    Abstract
    Knowing the time of change would narrow the search to find and identify the variables disturbing a process. Having this information, an appropriate corrective action could be implemented and valuable time could be saved. Multistage processes that are often observed in current manufacturing processes must be monitored to assure quality products. The change-point detection of such processes has not been proposes investigated yet. Thus, this dissertation proposes maximum likelihood step-change estimators of two kinds of these processes. First, a multistage process with variable quality characteristics is considered and formulated by the first-order auto-regressive model. For the location... 

    Developmental model of an automatic production of the human bronchial tree based on L-system

    , Article Computer Methods and Programs in Biomedicine ; Volume 132 , 2016 , Pages 1-10 ; 01692607 (ISSN) Davoodi, A ; Boozarjomehry, R. B ; Sharif University of Technology
    Elsevier Ireland Ltd  2016
    Abstract
    Background and objective: The human lungs exchange air with the external environment via the conducting airways. The application of an anatomically accurate model of the conducting airways can be helpful for simulating gas exchange and fluid distribution throughout the bronchial tree in the lung. Methods: In the current study, Lindenmayer system (L-system) has been formulated to generate the bronchial tree structure in a human lung. It has been considered that the structure of the bronchial tree is divided into two main segments: 1) The central airways (from the trachea to segmental bronchi) and 2) the dichotomous structure (from segmental bronchi to terminal bronchioles). Two sets of... 

    Lattice coding for multiple access channels with common message and additive interference

    , Article 2012 IEEE Information Theory Workshop, ITW 2012 ; 2012 , Pages 412-416 ; 9781467302234 (ISBN) Pourbabaee, M. F ; Emadi, M. J ; Davoodi, A. G ; Aref, M. R ; Sharif University of Technology
    2012
    Abstract
    In this paper, lattice based coding is used over two-user Gaussian state-dependent multiple access channel with common message for two channel models. First, it is assumed that the additive channel interference is noncausally known at both encoders. Exploiting a lattice encoding and decoding scheme, the effect of the interference is completely removed and the capacity region is achieved. Then, the multiple access channel with two additive interferences is considered in the case, where each interference is known noncausally to the associated transmitter. A pure lattice based encoding and decoding structure is proposed and an inner bound on the capacity region is derived which is valid for the... 

    Introduction to Developing, Modification, and Customization of the Guidelines for Replacement of Metal Patch Repairs with the Composite Patches

    , M.Sc. Thesis Sharif University of Technology Davoodi Moallem, Misam (Author) ; Abedian, Ali (Supervisor)
    Abstract
    The phenomenon of aging causes a great deal of damage to the airborne structures for which there is a specific maintenance instruction, or if an unexpected damage occurs in specific area of a structure, this damage must be repaired and a special repair process must be designed for it. However, due to the diversity of damages and also variations of the implemented loads, the load is transferred to other structural elements, hence, it is necessary to extend the life of the structure in order to identify these loaded elements and reinforce the applied forces. First, this phenomenon involves a design of a large number of metal patches, where a large number of drills have to be made in the body...