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    Optimizing constrained single period problem under random fuzzy demand

    , Article International Conference on Numerical Analysis and Applied Mathematics, ICNAAM 2008, Psalidi, Kos, 16 September 2008 through 20 September 2008 ; Volume 1048 , 2008 , Pages 43-46 ; 0094243X (ISSN) ; 9780735405769 (ISBN) Taleizadeh, A. A ; Shavandi, H ; Riazi, A ; Sharif University of Technology
    2008
    Abstract
    In this paper, we consider the multi-product multi-constraint newsboy problem with random fuzzy demands and total discount. The demand of the products is often stochastic in the real word but the estimation of the parameters of distribution function may be done by fuzzy manner. So an appropriate option to modeling the demand of products is using the random fuzzy variable. The objective function of proposed model is to maximize the expected profit of newsboy. We consider the constraints such as warehouse space and restriction on quantity order for products, and restriction on budget. We also consider the batch size for products order. Finally we introduce a random fuzzy multi-product... 

    An experimental evaluation of copper, steel and polypropylene tubes in solar water heaters with thermosyphonic flow

    , Article Applied Solar Energy (English translation of Geliotekhnika) ; Volume 45, Issue 1 , 2009 , Pages 65-69 ; 0003701X (ISSN) Riazi, M. R ; Razavi, J ; Sadeghi, A ; Javaheri, A ; Sharif University of Technology
    2009
    Abstract
    In this paper we report experimental results for the performance and rate of heat transfer in copper tubes in solar water heaters with thermosyphonic flow in continuation of experimental data reported in previous publications (Solar Energy, 2003, vol. 74, pp. 441-445, and Energy Sources, 1997, vol. 19, pp. 147-152). We also show a comparison between performances of three kinds of tubes: copper, polypropylene and steel under similar conditions. An analytical relation for calculation of rate of heat transfer in copper tubes is also presented in terms of Nusselt versus Reynolds and Prantdl numbers. A comparison of experimental data showed that performance of copper tubes is slightly better than... 

    A new insight into pore body filling mechanism during waterflooding in a glass micro-model

    , Article Chemical Engineering Research and Design ; Volume 151 , 2019 , Pages 100-107 ; 02638762 (ISSN) Rezaei Dehshibi, R ; Sadatshojaie, A ; Mohebbi, A ; Riazi, M ; Sharif University of Technology
    Institution of Chemical Engineers  2019
    Abstract
    By displacing oil in porous media with other fluid, different mechanisms of fluid displacing occur. The importance of understanding the trapping mechanisms like pore body filling is irrefutable. Pore body filling mechanism with a coordination number of four has different events like I0, I1, I2 and I3. Previous studies showed that the event of I0 occurs when the pore is only filled by a compressible non-wetting phase, but this study showed that this event could also occur by an incompressible non-wetting phase. Trapping mechanisms can be examined in a glass micro-model. In this research, a glass micro-model with three different patterns was used. Results showed that at two spots of the... 

    Experimental investigation of the influence of supercritical carbon dioxide and supercritical nitrogen injection on tertiary live-oil recovery

    , Article Journal of Supercritical Fluids ; Volume 117 , 2016 , Pages 260-269 ; 08968446 (ISSN) Lashkarbolooki, M ; Vaezian, A ; Zeinolabedini Hezave, A ; Ayatollahi, S ; Riazi, M ; Sharif University of Technology
    Elsevier  2016
    Abstract
    Generally, there are different enhanced oil recovery (EOR) methods. One of the most promising EOR method is the gas injection especially carbon dioxide (CO2) injection since it introduce several unique characteristic desired for higher tertiary oil recovery. In this study, the performance and feasibility of supercritical carbon dioxide (SC-CO2) and supercritical nitrogen (SC-N2) injection to enhanced oil recovery was investigated. In this regard, swelling tests and core flooding experiments were performed to find out whether the injections of these gases are efficient to recover trapped oil in the reservoir. Based on the experimental results, the possible active mechanisms were discussed on... 

    Alumina-copper eutectic bond strength: contribution of preoxidation, cuprous oxides particles and pores

    , Article Scientia Iranica ; Volume 16, Issue 3 B , 2009 , Pages 263-268 ; 10263098 (ISSN) Ghasemi, H ; Faghihi Sani, M. A ; Kokabi, A. H ; Riazi, Z ; Sharif University of Technology
    2009
    Abstract
    The influences of cupric oxide layer thickness, cuprous oxide particles and pores on the mechanical properties and micro structure of an alumina-copper eutectic bond have been investigated. The furnace, atmosphere in the. first stage was argon gas with 2 × 10-6 atm oxygen partial pressure. In the second stage, the. furnace atmosphere was the. same as the first stage except that the cooling interval was between 900-100l°C and the hydrogen gas was injected into the. furnace, atmosphere. Finally, in the last stage, a vacuum furnace with 5 × 10-8 atra pressure was chosen for the bonding procedure. The peel strength of first stage specimens shows that a, cupric oxide layer with 320 ± 25 ran... 

    Roles of preoxidation, Cu2O particles, and interface pores on the strength of eutectically bonded Cu/α-Al2O3

    , Article Materials and Design ; Volume 30, Issue 4 , 2009 , Pages 1098-1102 ; 02641275 (ISSN) Ghasemi, H ; Kokabi, A. H ; Faghihi Sani, M. A ; Riazi, Z ; Sharif University of Technology
    2009
    Abstract
    The influences of CuO layer thickness, Cu2O particles, and pores on mechanical properties and microstructure of alumina-copper eutectic bond have been investigated. The furnace atmosphere in the first stage was argon gas with 2 × 10-6 atm oxygen partial pressure. In the second stage, the furnace atmosphere was same as the first stage except for the cooling interval between 900 and 1000 °C, the hydrogen gas was injected into furnace atmosphere. Finally, in the last stage a vacuum furnace with 5 × 10-8 atm pressure was chosen for bonding procedure. Peel strength of first stage specimens shows that CuO layer with 320 ± 25 nm thick generates the maximum peel strength (13.1 ± 0.3 kg/cm) in joint... 

    Alumina - copper eutectic bond strength: Contribution of preoxidation, cuprous oxides particles, and pores

    , Article 16th International Federation for Heat Treatment and Surface Engineering Congress, Brisbane, QLD, 30 October 2007 through 2 November 2007 ; Volume 32 , 2007 , Pages 90-97 ; 08832900 (ISSN) Ghasemi, H ; Kokabi, A. H ; Faghihi Sani, M. A ; Riazi, Z ; Sharif University of Technology
    2009
    Abstract
    The influences of cupric oxide layer thickness, cuprous oxide particles, and pores on mechanical properties and microstructure of alumina-copper eutectic bond have been investigated. The furnace atmosphere in the first stage was argon gas with 2 × 10-6 atm oxygen partial pressure. In the second stage, the furnace atmosphere was same as the first stage unless that in cooling between 900-1000 °C, the hydrogen gas was purged in furnace atmosphere. Finally, in the last stage a vacuum furnace with 5 × 10 -8 atm pressure was chosen for bonding procedure. Peel strength of first stage specimens shows that cupric oxide layer with 320 ± 25 nm thick generates the maximum peel strength (13.1 ± 0.3... 

    New insight on dynamic behavior of swelling and bond number of light and heavy crude oil during carbonated water flooding

    , Article European Physical Journal Plus ; Volume 135, Issue 1 , January , 2020 Lashkarbolooki, M ; Zeinolabedini Hezave, A ; Riazi, M ; Ayatollahi, S ; Sharif University of Technology
    Springer  2020
    Abstract
    Improving oil recovery and decreasing greenhouse gas emissions are two important attractive features of CO2-enriched water injection into oil reservoirs. Regarding these unique features, the main objective of this study was concentrated to evaluate the swelling behavior of crude oil as a fundamental mechanism of carbonated water (CW) flooding. To achieve these goals, the swelling and Bond number of light and heavy crude oils (namely LCO and HCO, respectively) are measured and compared to each other. The results obtained from the measured swelling factors of crude oil/CW show some complicated behaviors. That is, as temperature increases the swelling factor decreases at low pressure... 

    Laminar premixed V-shaped flame response to velocity and equivalence ratio perturbations: Investigation on kinematic response of flame

    , Article Scientia Iranica ; Volume 18, Issue 4 B , 2011 , Pages 913-922 ; 10263098 (ISSN) Riazi, R ; Farshchi, M ; Sharif University of Technology
    2011
    Abstract
    The response of a rod-stabilized, V-shaped, premixed flame to upstream velocity and equivalence ratio perturbations was characterized as a function of excitation frequency. The response of the flame to equivalence ratio perturbations was calculated, assuming that the heat release response is controlled by contributions from three disturbances. These disturbances include flame speed, heat of reaction and flame area. Using an analytical model, based on linearization of the front tracking equation for inclined flames, the kinematics of a V-flame anchored on a central obstacle was investigated and its response was compared with that of a conical flame. The results suggest that the phase response... 

    Investigation of Magnetic and Electromagnetic Methods in Electron Beam Shaping and their Scaling Behavior for Nanometric field Emitters

    , M.Sc. Thesis Sharif University of Technology Riazi, Arash (Author) ; Rashidian, Bizhan (Supervisor)
    Abstract
    Nowadays electron beams have extensive applications in electon-optic devices such as microwave devices, electron microscopes and flat displays. So shaping and confinment of electron beams is of great importance. In the other hand, scaling of electron emitters to atomic limit causes new chalanges in reliability and beam shaping. Designing electron optic devices for nanoscale emitters needs great knowledge regarding materials properties and electron optic systems behavior in nano scale. In this study, beside providing basic optics of electron beam and effects Of external electronmagnetic fields, properties of electron optical devices
    Considering nano scale limitations is considered. In... 

    Investigations on Stability of Premixed Flames in Turbine Engines

    , Ph.D. Dissertation Sharif University of Technology Riazi, Rouzbeh (Author) ; Farshchi, Mohammad (Supervisor)
    Abstract
    This thesis is a complementary experimental and theoretical investigation on stability of premixed flames and a study of combustion instability and combustion dynamics in a swirl-stabilized combustor, aiming to understand the fundamental mechanisms responsible for combustion oscillations in gas turbine combustors. Theoretical investigations on acoustic modeling of a simple combustor and a study on kinematic response of premixed flames to flow perturbations have been discussed in the first part of this work. In another part of thesis, experimental studies on the response of premixed flames to acoustic perturbations have been performed. In addition, experimental investigations on combustion... 

    Experimental investigation of secondary and tertiary oil recovery from fractured porous media

    , Article Journal of Petroleum Exploration and Production Technology ; Volume 3, Issue 3 , September , 2013 , Pages 179-188 ; 21900558 (ISSN) Maroufi, P ; Ayatollahi, S ; Rahmanifard, H ; Jahanmiri, A ; Riazi, M ; Sharif University of Technology
    2013
    Abstract
    Naturally fractured reservoirs (NFRs) contribute in large extent to oil and gas production to the ever increasing market demand of fossil energy. It is believed that the vertical displacement of oil during gas injection assisted by gravity drainage (GAGD) is one of the most efficient methods for oil recovery in these reservoirs. Hence, in this work, unconsolidated packed models of cylindrical geometry surrounded by fracture were utilized in order to perform a series of flow visualization experiments during which the contribution of different parameters such as the extent of matrix permeability, physical properties of oil (viscosity, density, and surface tension) and the withdrawal rate was... 

    Quartic balance theory: Global minimum with imbalanced triangles

    , Article Physical Review E ; Volume 102, Issue 1 , 2020 Kargaran, A ; Ebrahimi, M ; Riazi, M ; Hosseiny, A ; Jafari, G. R ; Sharif University of Technology
    American Physical Society  2020
    Abstract
    Balance theory proposed by Heider for the first time modeled triplet interaction in a signed network, stating that relationships between two people, friendship or enmity, is dependent on a third person. The Hamiltonian of this model has an implicit assumption that all triads are independent, meaning that the type of each triad, being balanced or imbalanced, determined apart from the state of other triads. This independence forces the network to have completely balanced final states. However, there exists evidence indicating that real networks are partially balanced, raising the question of what is the mechanism preventing the system to be perfectly balanced. Our suggestion is to consider a... 

    Quantitative Elemental Analysis Using Whole Spectral Information (with GA and MLR Methods) of Proton Induced Prompt Gamma-Rays Simulated Using Geant4 Toolkit

    , Article Frontiers in Biomedical Technologies ; Volume 10, Issue 1 , 2023 , Pages 78-87 ; 23455829 (ISSN) Saheli, F ; Vosoughi, N ; Riazi, Z ; Rasouli, F. S ; Jowkar, A ; Sharif University of Technology
    Tehran University of Medical Sciences  2023
    Abstract
    Purpose: Online determination of the elemental composition of tissues near the Bragg peak is a challenge in proton therapy related studies. In the present work, an analysis method based on the whole spectral information is presented for the quantitative determination of the elemental composition (weight %) of an irradiated target from its emitted Prompt Gamma (PG) spectrum. Materials and Methods: To address this issue, four test phantoms with different weights (%) of 12C, 16O, 20Ca, and 14N elements were considered. The simulated PG spectra were recorded using 3 × 3 inch NaI detectors. A library consisting of the spectra of single-element phantoms as well as the spectra of test-irradiated... 

    Analysis of resistance spot welding process parameters effect on the weld quality of three-steel sheets used in automotive industry: Experimental and finite element simulation

    , Article International Journal of Engineering, Transactions A: Basics ; Volume 33, Issue 1 , 2020 , Pages 148-157 Farrahi, G. H ; Reza Kashyzadeh, K ; Minaei, M ; Sharifpour, A ; Riazi, S ; Sharif University of Technology
    Materials and Energy Research Center  2020
    Abstract
    In the present research, the effects of spot-welding process parameters on the nugget diameter and electrode penetration depth of spot-welded joints were investigated. To achieve this, a spot-welded joint of three-thin sheet low carbon steels (same thicknesses of 0.8 mm) was simulated as an electerical-thermal-mechanical coupling of 3D finite element model. After validating the finite element simulation presented in this study by comparison with the experimental results for the spot diameter, various cases of spot welds were analyzed based on the design on experiment (i.e., Taguchi method). Six variables including electrode force, electric current, and quadrilateral times (squeeze, up-slope,... 

    The impacts of aqueous ions on interfacial tension and wettability of an asphaltenic-acidic crude oil reservoir during smart water injection

    , Article Journal of Chemical and Engineering Data ; Vol. 59, issue. 11 , 2014 , pp. 3624-3634 ; ISSN: 00219568 Lashkarbolooki, M ; Ayatollahi, S ; Riazi, M ; Sharif University of Technology
    2014
    Abstract
    The use of adjusted/optimized saline water categorized into two different classes namely smart water (SW) and low salinity (LoSal) water injection has been proposed for more oil recovery from specific types of oil reservoirs. There are possible mechanisms concerning SW flooding that have been proposed in the literature, some of them are still subject to more examination. In this study, an experimental investigation is performed to determine the influence of type and amount of salt to the surface properties including interfacial tension (IFT) and contact angle (CA) of aqueous solution + acidic and asphaltenic crude oil + carbonate rock systems. For this purpose, the concentration of different... 

    Investigation of oil recovery and CO2 storage during secondary and tertiary injection of carbonated water in an Iranian carbonate oil reservoir

    , Article Journal of Petroleum Science and Engineering ; Volume 137 , 2016 , Pages 134-143 ; 09204105 (ISSN) Shakiba, M ; Ayatollahi, S ; Riazi, M ; Sharif University of Technology
    Elsevier  2016
    Abstract
    Gas injection process for more oil recovery and in particular CO2 injection is well-established method to increment oil recovery from underground oil reservoirs. CO2 sequestration which takes place during this enhanced oil recovery (EOR) method has positive impact on reducing the greenhouse gas emission which causes global warming. Direct gas injection into depleted oil reservoirs, encounters several shortcomings such as low volumetric sweep efficiency, early breakthrough (BT) and high risk of gas leakage in naturally fractured carbonate oil reservoirs. Carbonated water injection (CWI) has been recently proposed as an alternative method to alleviate the problems associated with gas... 

    Mechanistic study on the dynamic interfacial tension of crude oil + water systems: Experimental and modeling approaches

    , Article Journal of Industrial and Engineering Chemistry ; Volume 35 , 2016 , Pages 408-416 ; 1226086X (ISSN) Lashkarbolooki, M ; Ayatollahi, S ; Riazi, M ; Sharif University of Technology
    Korean Society of Industrial Engineering Chemistry  2016
    Abstract
    This study investigates dynamic interfacial tension (DIFT) of acidic crude oil (ACO) and non acidic/basic crude oils (BCO) + deionized water (DW) as a function of pressure from 500 to 4000 psi, and temperature from 30 to 80 °C using an axisymmetric drop shape analysis (ADSA) technique. DIFTs are also modeled using dynamic adsorption model, mono-exponential decay model, and empirical equations. The results showed that if a reduction in the surface excess concentration due to increasing temperature overlooks the total entropy of the molecules in the system, an increase in IFT would be expected  

    Mechanistical study of effect of ions in smart water injection into carbonate oil reservoir

    , Article Process Safety and Environmental Protection ; Volume 105 , 2017 , Pages 361-372 ; 09575820 (ISSN) Lashkarbolooki, M ; Ayatollahi, S ; Riazi, M ; Sharif University of Technology
    Institution of Chemical Engineers  2017
    Abstract
    The concerns for water availability, affordability and environmental consideration have motivated more research on the development of smart water injection for enhanced oil recovery process. Although wettability alteration has been considered as the dominant mechanism, there is an ample space in this area needs to be explored more. Therefore, a systematic series of experiments is designed and performed to examine the effect of salinity and ion type on the wettability of the carbonate rock surface to find the active mechanisms. For this purpose, the concentrations of different salts including NaCl, KCl, CaCl2 and MgCl2 are examined during 10 days of soaking for salts concentrations range of... 

    Underground natural gas storage in a low quality gas reservoir - Produced gas quality control by rate optimization

    , Article 79th EAGE Conference and Exhibition 2017: Energy, Technology, Sustainability - Time to Open a New Chapter, 12 June 2017 through 15 June 2017 ; 2017 ; 9789462822177 (ISBN) Ansari, N ; Ayatollahi, S ; Riazi, M ; Sharif University of Technology
    European Association of Geoscientists and Engineers, EAGE  2017
    Abstract
    Due to increasing demand for natural gas, storage plan development in order to cope with seasonal gas fluctuations and ensure constant gas supply during a year, has recently become highly indispensable. However, developing underground gas storage (UGS) facility is so costly which may sometimes discourage the investment.One of the main cost items while fulfilling a UGS project can be attributed to cushion gas; this is part of gas inventory which remainspermanently in the storage field in order to maintain pressure and provide adequate deliverability rate during production cycles.For this reason, UGS in low quality gas reservoirs has been recentlyproposed. In such a case, native reservoir gas...