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razeghi-jahromi--dorsa
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Total 224 records
Applying feature selection and machine learning techniques to estimate the biomass higher heating value
, Article Scientific Reports ; Volume 13, Issue 1 , 2023 ; 20452322 (ISSN) ; Ranjbar, F ; Razeghi Jahromi, D ; Sharif University of Technology
Nature Research
2023
Abstract
The biomass higher heating value (HHV) is an important thermal property that determines the amount of recoverable energy from agriculture byproducts. Precise laboratory measurement or accurate prediction of the HHV is essential for designing biomass conversion equipment. The current study combines feature selection scenarios and machine learning tools to establish a general model for estimating biomass HHV. Multiple linear regression and Pearson’s correlation coefficients justified that volatile matter, nitrogen, and oxygen content of biomass samples have a slight effect on the HHV and it is better to ignore them during the HHV modeling. Then, the prediction performance of random forest,...
Developing an Optimization Model for the Adaptation of Iran's Energy System to Climate Change
, M.Sc. Thesis Sharif University of Technology ; Khajehpour, Hossein (Supervisor)
Abstract
This study develops an optimization model to assess and enhance the resilience of Iran’s energy system under future climate change conditions. Using the OSeMOSYS framework, the impacts of projected changes in temperature, precipitation, solar radiation, and wind speed on the performance of power generation technologies (solar, wind, hydro, and thermal) as well as on electricity demand patterns across Iran’s climatic regions were analyzed up to 2050. Four main scenarios were designed: (1) a baseline scenario without climate or environmental constraints, (2) an emission reduction scenario with carbon limits but no adaptation, (3) an adaptation scenario considering direct climatic effects on...
Decontamination of congo red dye from aqueous solution using nanoclay/chitosan-graft-gelatin nanocomposite hydrogel
, Article Journal of Molecular Liquids ; Volume 395 , 2024 ; 01677322 (ISSN) ; Naimi-Jamal, M. R ; Jahanbakhshi, M ; Khalafvandi, S. A ; Alian, M ; Razeghi Jahromi, D ; Sharif University of Technology
Elsevier
2024
Abstract
In this study, bentonite nanoclay (BNC) impregnated chitosan-g-gelatin (CS-g-GEL/BNC) nanocomposite hydrogels were prepared with multi-features including being cost-effective, high-performance, biodegradable, and easy to separate for Congo red (CR) dye adsorption. Various characterization techniques, including FTIR, XRD, SEM, TGA, and EDX, were used to verify the successful formulation of the prepared hydrogels. The results revealed that the thermal stability of CS-g-GEL/BNC nanocomposite hydrogel was improved compared to CS-g-GEL hydrogel. CR dye also reached its equilibrium adsorption quickly and effectively at 60 min. When bentonite clay nanoparticles content was increased to 10 %, the...
TPU/graphene nanocomposites: effect of graphene functionality on the morphology of separated hard domains in thermoplastic polyurethane
, Article Polymer ; Volume 148 , 18 July , 2018 , Pages 169-180 ; 00323861 (ISSN) ; Pircheraghi, G ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Graphene nanoplatelets with different surface functional groups and polarity were prepared by Hummer's method and electrochemical exfoliation of graphite in two aqueous acids. The XRD, FTIR and sedimentation tests performed to characterize the polarity of the prepared graphenes. The highest polarity was associated with the sample prepared by Hummer's method and the sample synthesized by electrochemical exfoliation in nitric acid medium showed the moderate polarity. Meanwhile, the sample prepared in sulfuric acid medium showed the lowest polarity. Then thermoplastic polyurethane (TPU)/graphene nanocomposite films were fabricated with solvent exchange method. While the dispersion state and...
Investigate the Oscillations and Parameters of Bubble Induced by Laser in the Prescence of Acoustic Field
, M.Sc. Thesis Sharif University of Technology ; Sadighi-Bonabi, Rasoul (Supervisor)
Abstract
Sonoluminescence is called a phenomenon in which a gas bubble is trapped in an antinode of a pressure field by a driven periodic acoustical field in a fluid and oscillations and at the end of each collapse, emits a flash. For this emission various conditions for stability must be satisfied, like diffusion stability, shape stability and positional stability. Another method to produce the bubbles is applications of a focused laser beam. In this method, a laser pulse is focused into a transparent buffer liquid like water and bubbles which are induced by the laser are so called Laser Induced Single Cavitation Bubble Luminescence (LI-SCBL). In the presence of the laser, the fluid acts as...
Study on the Exfoliation of Graphite into Graphene by Electrochemical Method and Its Application in Thermoplastic Polyurethane Nanocomposite
, M.Sc. Thesis Sharif University of Technology ; Pircheraghi, Gholamreza (Supervisor)
Abstract
Graphene is two dimensional nanomaterial, single layer of carbon atoms that exhibited excellent properties like high electrical conductivity and stiffness, but producing graphene and obtaining a good dispersion of graphene in a polymer matrix is still a major challenge. In this study by using the electrochemical route several graphene with different degree of oxidation produced in different electrolyte medium. According to XRD data, product of electrochemical exfoliation in dilute HNO3 medium includes 50% few-layer graphene (5 layers) and 25% GO and the rest are multi-layer graphene. Nonsolvent induced phase separation method were used to prepare TPU/Graphene nanocomposite. Different methods...
Correlation between trunk-pelvis inter-segmental coordination parameters during walking and disability level in chronic low back pain patients
, Article Journal of Biomedical Physics and Engineering ; Volume 8, Issue 2 , 2018 , Pages 193-202 ; 22517200 (ISSN) ; Kamali, F ; Razeghi, M ; Haghpanah, A ; Sharif University of Technology
Shiraz University of Medical Sciences
2018
Abstract
Background: Chronic low back pain (CLBP) disability has been particularly frustrating because its treatment has been a great therapeutic challenge. Disability has been suggested to depend on different factors that should be found and considered in the medical management. The inter-segmental coordination is often impaired in CLBP subjects; however, to the best of our knowledge, there is no evidence about the relationship between the existence of coordination problems and disability in CLBP patients. Objective: To evaluate the correlation between sagittal plane trunk-pelvis intersegmental coordination parameters during walking and disability level in CLBP patients. Methods: Kinematic data were...
The effect of viscosity, applied frequency and driven pressure on the laser induced bubble luminescence in water-sulfuric acid mixtures
, Article Physics Letters, Section A: General, Atomic and Solid State Physics ; Volume 380, Issues 27–28 , June , 2016 , Pages 2219–2226 ; 03759601 (ISSN) ; Alijan Farzad Lahiji, F ; Razeghi, F ; Sharif University of Technology
Elsevier
2016
Abstract
Production and oscillation of sonoluminescence bubbles by laser pulse in the presence of acoustic field in water and different concentrations of sulfuric acid are investigated. In the presence of acoustic field, the laser causes variable speed of sound, surface tension and density; and the host liquid acts as a compressible one and strongly affects the bubble's dynamics equations. The effect of various concentrations of sulfuric acid as a host liquid on the oscillation of bubble radius, bubble wall velocity and bubble interior temperature is studied. Furthermore, the effect of applied frequency on LI-SCBL in the presence of the acoustic field is investigated and an optimum sound wave...
Generating the Activation Patterns of the Leg Muscles during Human Locomotion Using the Central Pattern Generators as a Control Structure
, Article Iranian Journal of Science and Technology - Transactions of Mechanical Engineering ; Volume 40, Issue 2 , 2016 , Pages 87-94 ; 22286187 (ISSN) ; Farahmand, F ; Zohoor, H ; Razeghi, M ; Sharif University of Technology
Shiraz University
2016
Abstract
The central pattern generators have been considered as a method to simplify the control of the complex rhythmic motions, e.g., walking, by the central nervous system. In this study, a control structure was designed to control the soleus and tibialis anterior muscles in a complete gait cycle. The activation patterns of the muscles were measured experimentally and used as the reference signals of a tracking problem. The hip angle and ground reaction force were also used as a feedforward. The feedback from the Golgi tendon acted as a regulator of muscle activity. The controller was applied to two gait trials. The results indicated that the designed controller was capable of tracking the...
Comparison of the trunk-pelvis and lower extremities sagittal plane inter-segmental coordination and variability during walking in persons with and without chronic low back pain
, Article Human Movement Science ; Volume 52 , 2017 , Pages 55-66 ; 01679457 (ISSN) ; Kamali, F ; Razeghi, M ; Haghpanah, S. A ; Sharif University of Technology
Elsevier B.V
2017
Abstract
Inter-segmental coordination can be influenced by chronic low back pain (CLBP). The sagittal plane lower extremities inter-segmental coordination pattern and variability, in conjunction with the pelvis and trunk, were assessed in subjects with and without non-specific CLBP during free-speed walking. Kinematic data were collected from 10 non-specific CLBP and 10 non-CLBP control volunteers while the subjects were walking at their preferred speed. Sagittal plane time-normalized segmental angles and velocities were used to calculate continuous relative phase for each data point. Mean absolute relative phase (MARP) and deviation phase (DP) were derived to quantify the trunk-pelvis and bilateral...
Development of Energy Supply Optimization Model in a Steel Production Unit in Order to Overcome Short Fall in Natural Gas Supply
, M.Sc. Thesis Sharif University of Technology ; Khajehpour, Hossein (Supervisor) ; Sattari, Sorena (Supervisor)
Abstract
Energy supply optimization in large scale steel industries among the most energy intensive sectors is increasingly critical for achieving an optimal energy portfolio that compensates for supply imbalances and prevents production shutdowns and the associated financial losses. This research aims to develop an energy supply optimization model to ensure a reliable response to the multi-vector energy demands of an integrated iron and steel plant. The central research question addresses how diverse technologies and resource management strategies can be combined to simultaneously meet the demands for electricity, heat, water, and reducing gas under varying resource constraints. The innovation of...
Fuzzy reliability optimization models for redundant systems [electronic resource]
, Article International Journal of Industrial engineering ; July 2008, Vol. 4, No. 7, 1-9 ; Eshghi, Kourosh ; Eshraghniaye Jahromi, Abdolhamid ; Sharif University of Technology
Abstract
In this paper, a special class of redundancy optimization problem with fuzzy random variables is presented. In this model, fuzzy random lifetimes are considered as basic parameters and the Er-expected of system lifetime is used as a major type of system performance. Then a redundancy optimization problem is formulated as a binary integer programming model. Furthermore, illustrative numerical examples are also given to clarify the methods discussed in this paper
Shared information in a serial inventory system [electronic resource]
, Article International Journal of Advanced Operations Management - IJAOM ; 2011 Vol.3, No.2 pp.101 - 121 ; Eshraghniaye Jahromi, Abdolhamid ; Eshghi, Kourosh ; Sharif University of Technology
Abstract
In this study, a supply chain model consisting of a single product, one supplier and one retailer is considered. Transportation times are constant and demands at the retailer are assumed to be generated by a stationary Poisson process. Demands not covered immediately from inventory are backordered. The retailer carries inventory and replenishes stock according to a (Q, R) policy. The supplier has online information about the demand at the retailer and uses this information to replenish its stock. The order size at the supplier is a multiple integer to the retailer's order size. Considering order costs for the retailer and the supplier, we derive the exact cost function for this inventory...
A resource constrained project scheduling problem with fuzzy random duration [electronic resource]
, Article Journal of Uncertain Systems ; Vol.4, No.2, pp.123-132, 2010 ; Eshghi, Kourosh ; Eshragh Jahromi, Abdolhamid ; Sharif University of Technology
Abstract
In this paper, first a fuzzy random resource-constrained project scheduling problem is presented. The object of the problem is to find the optimal scheduling of project activities. In this model, duration of project activities is a fuzzy random variable. Then, the proposed model is formulated by using the expected value of fuzzy random variables as an IP model. An illustrative example is also provided to clarify the concept. © 2010 World Academic Press, UK. All rights reserved
On exponential flocking to the virtual leader in network of agents with double-integrator dynamics
, Article Journal of Dynamic Systems, Measurement and Control, Transactions of the ASME ; Volume 135, Issue 3 , 2013 ; 00220434 (ISSN) ; Haeri, M ; Sharif University of Technology
2013
Abstract
This paper considers flocking to the virtual leader in network of agents with double-integrator. A locally linear algorithm is employed which guarantees exponential flocking to the virtual leader. A lower bound for flocking rate is calculated which is independent of the initial conditions. Simulations are provided to validate the result and it is shown that the calculated rate is not over bound the actual convergence rate. The effect of coefficients of algorithm is investigated and it is shown that the similar results can be inferred from the calculated formula for the convergence rate. Copyright
Semi active vibration control of a passenger car using magnetorheological shock absorber
, Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, Istanbul, 12 July 2010 through 14 July 2010 ; Volume 3 , 2010 , Pages 21-27 ; 9780791849170 (ISBN) ; Zabihollah, A ; Sharif University of Technology
2010
Abstract
A novel semi-active control system for suspension systems of passenger car using Magnetorheological (MR) damper is introduced. The suspension system is considered as a mass-spring model with an eight-degrees-of-freedom, a passive damper and an active damper. The semi-active vibration control is designed to reduce the amplitude of automotive vibration caused by the alteration of road profile. The control mechanism is designed based on the optimal control algorithm, Linear Quadratic Regulator (LQR). In this system, the damping coefficient of the shock absorber changes actively trough inducing magnetic field. It is observed that utilizing the present control algorithm may significantly reduce...
Replacement-repair policy based on a simulation model for multi-state deteriorating products under warranty
, Article Scientia Iranica ; Volume 16, Issue 1 E , 2009 , Pages 26-35 ; 10263098 (ISSN) ; Vahdani, H ; Sharif University of Technology
2009
Abstract
In this paper, a replacement-repair model is developed to study a warranty servicing policy for a class of multi-state deteriorating and repairable products, based on a computer simulation analysis. In each working state there is a determined probability for transition to each of the subsequent states, given that it has made a transition out of that state. There are two parameters that determine the manufacturer's decision to repair or replace a failed item, assuming that the buyer's claim is valid; the deterioration degree of the item and the length of the residual warranty period. Beside these two parameters, other inputs to the model are: the number of working and failure states, the...
Full characterization of a spin liquid phase: From topological entropy to robustness and braid statistics
, Article Journal of Physics A: Mathematical and Theoretical ; Volume 50, Issue 14 , 2017 ; 17518113 (ISSN) ; Langari, A ; Sharif University of Technology
Institute of Physics Publishing
2017
Abstract
We use the topological entanglement entropy (TEE) as an efficient tool to fully characterize the Abelian phase of a Z2 ×Z2 spin liquid emerging as the ground state of topological color code (TCC), which is a class of stabilizer states on the honeycomb lattice. We provide the fusion rules of the quasiparticle (QP) excitations of the model by introducing single- or two-body operators on physical spins for each fusion process which justify the corresponding fusion outcome. Besides this, we extract the TEE from Renyi entanglement entropy (EE) of the TCC, analytically and numerically by finite size exact diagonalization on the disk shape regions with contractible boundaries. We obtain that the EE...
A new model for reliability optimization of series-parallel systems with non-homogeneous components
, Article Reliability Engineering and System Safety ; Volume 157 , 2017 , Pages 101-112 ; 09518320 (ISSN) ; Eshraghniaye Jahromi, A ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
In discussions related to reliability optimization using redundancy allocation, one of the structures that has attracted the attention of many researchers, is series-parallel structure. In models previously presented for reliability optimization of series-parallel systems, there is a restricting assumption based on which all components of a subsystem must be homogeneous. This constraint limits system designers in selecting components and prevents achieving higher levels of reliability. In this paper, a new model is proposed for reliability optimization of series-parallel systems, which makes possible the use of non-homogeneous components in each subsystem. As a result of this flexibility,...
Optimization of multi-objective redundancy allocation problem with non-homogeneous components
, Article Computers and Industrial Engineering ; Volume 108 , 2017 , Pages 111-123 ; 03608352 (ISSN) ; Feizabadi, M ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
In many real world optimization problems, including Redundancy Allocation Problem (RAP), there is a need to optimize more than one objective function simultaneously. In this paper, a new multi-objective formulation is presented for the RAP by considering the reliability and cost of the system as the objective functions. The previous formulations have been proposed based on the assumption that all components of a subsystem are homogeneous. This constraint leads to an increase in the designing cost and prevents from reaching to higher quantities of the system reliability. The presented formulation in this research provides an opportunity for the subsystems components to be non-homogeneous in...