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A platform-based structure for group purchasing with bundles of items
, Article International Journal of Systems Science: Operations and Logistics ; Volume 10, Issue 1 , 2023 ; 23302674 (ISSN) ; Eshghi, K ; Rafiee, M ; Sharif University of Technology
Taylor and Francis Ltd
2023
Abstract
Despite the growth of group purchasing, few studies consider group purchasing with bundled products. Generally, an individual buyer may be reluctant to buy a bundle and prefer to buy a portion of it. By group buying, buyers purchase their products with lower price. We proposed a group purchasing structure for bundles of items in which buyers’ purchasing power is a function of time and bundles’ expiration date. A platform is also considered that charges sellers after selling their bundles. Three strategies are proposed in terms of three problems. In problem (I), a group of buyers wants to buy those products whose bundle price they can pay for in full and maximise their total savings. In...
The multi-depot traveling purchaser problem with shared resources
, Article Sustainability (Switzerland) ; Volume 14, Issue 16 , 2022 ; 20711050 (ISSN) ; Eshghi, K ; Rafiee, M ; Van Woensel, T ; Sharif University of Technology
MDPI
2022
Abstract
Using shared resources has created better opportunities in the field of sustainable logistics and procurement. The Multi-Depot Traveling Purchaser Problem under Shared Resources (MDTPPSR) is a new variant of the Traveling Purchaser Problem (TPP) in sustainable inbound logistics. In this problem, each depot can purchase its products using the shared resources of other depots, and vehicles do not have to return to their starting depots. The routing of this problem is a Multi-Trip, Open Vehicle Routing Problem. A tailored integer programming model is formulated to minimize the total purchasers’ costs. Considering the complexity of the model, we have presented a decomposition-based algorithm...
The Multi -vehicle Traveling Purchaser Problem with Priority in Purchasing and Uncertainty in Demand
, M.Sc. Thesis Sharif University of Technology ; Eshghi, Kourosh (Supervisor)
Abstract
Procurement field and supplier’s selection are key decisions in the supply chain in today's business environment.In this problem, both procurement and transportation costs are important. The Traveling Purchasing Problem (TPP) belongs to this field of study. In spite of many researches in the TPP, most of the researches are confined to one single purchaser. In this research, a new variant of Traveling Purchaser Problem is proposed with priority in purchasing. The priority policy is assumed for every single of products and the purchasers’ objective is to meet all of the demands according to their priority and vehicle's capacity in the lowest cost. In this regard, the purchaser has to buy the...
The Multi-Depot Traveling Purchaser Problem with Shared Resources
, Ph.D. Dissertation Sharif University of Technology ; Eshghi, Kourosh (Supervisor) ; Rafiee, Majid (Supervisor)
Abstract
The Multi-Depot Traveling Purchaser Problem under Shared Resources (MDTPPSR) is a new variant of the Traveling Purchaser Problem (TPP). In this problem, each depot can purchase its products using the shared resources of other depots, and vehicles do not have to return to their starting depots. The routing of this problem is a Multi-Trip, Open Vehicle Routing Problem. A tailored integer programming model is formulated to minimize the total purchasers’ costs. Considering the complexity of the model, we have presented a decomposition-based algorithm that breaks down the problem into two phases. In the first phase, tactical decisions regarding supplier selection and the type of collaboration are...
A new developed semi-full-scale approach to facilitate the CFD simulation of shell and tube heat exchangers
, Article Chemical Engineering Science ; Volume 245 , 2021 ; 00092509 (ISSN) ; Abdollahpour, M. S ; Hasanpour Matkolaei, M ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
The full-scale CFD simulations may not be recommended in preliminary steps of STHEs’ design and sensitivity analyses because of heavy computations. This work benefits from the sequential geometry repetitions in STHEs and presents a new semi-full-scale approach, which alleviates the need for full-scale simulation of STHEs. This approach first isolates the smallest zone, say block, which is sequentially repeated in the STHE domain. Second, this block is carefully simulated considering various thermal and flow working conditions. Third, the data collected from these CFD simulations are used to generate the required thermal and flow correlations for the chosen block at various working...
The multi-vehicle travelling purchaser problem with priority in purchasing and uncertainty in demand
, Article International Journal of Logistics Systems and Management ; Volume 39, Issue 3 , June , 2021 , Pages 359-389 ; 17427967 (ISSN) ; Eshghi, K ; Sharif University of Technology
Inderscience Publishers
2021
Abstract
The multi-vehicle travelling purchaser problem with priority in purchasing (MTPP-PIP) is a new variant of the classic travelling purchaser problem (TPP) in which the set of products is divided into different priority groups. The purpose of this article is to find the least cost cycles in which each product should be purchased according to its predefined priority. To fit the model with the real world further, multiple purchasers (multi-vehicle) and uncertainty in the products demands are assumed. In this paper, a mathematical programming formulation is developed based on a clustered supplier graph whereby the suppliers are categorised into different clusters according to their corresponding...
Subsidy cut and its effect on tehran electricity company: A system dynamics approach
, Article Proceedings of the 2012 - Summer Computer Simulation Conference, SCSC 2012, Part of SummerSim 2012 Multiconference ; Volume 44, Issue 10 , 2012 , Pages 113-120 ; 9781618399847 (ISBN) ; Fard, S. Z
2012
Abstract
In recent years, subsidy payment has been made a main challenge for governments due to growth of population and energy price in global markets. Targeted subsidy plan has been implemented in Iran since last year, and this article discusses its effects on costs and revenues of Tehran Electricity Company as one of the major subdivisions of Iran's electricity industry. In the new system, structural changes have been made in electricity tariffs, so it is not possible to predict the future trends in electricity consumption only based on the past consumptions. In order to model the decision making structure in the recent conditions, a system dynamics method is applied. In addition to modeling the...
Thermal Analysis of Dry Friction Clutch and its Effect in Torque Transmission
, M.Sc. Thesis Sharif University of Technology ; Kazemzadeh Hannani, Siamak (Supervisor)
Abstract
For optimum designing of dry friction clutch, we should taking into account a lot of parameters, in order to the clutch have good efficiency in torque transmission and power train. These parameters include: the type of friction plate and the mechanical properties, Clutch geometry, diaphragm spring and its ability to make pressure. In this project, the goal is the analysis of effect of different parameters in clutch's temperature distribution and effect of these issues in torque transmission. In next step, the clutch's temperature distribution analyzed by changing the friction plate (ceramic), pressure applied and relative round in order to gain optimum properties of clutch. These works done...
Evaluating of Damages for Surface Tanks under Blast Loadings
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofooei, Fayaz (Supervisor)
Abstract
The on grade flexible steel storage tanks are extensively used in oil refineries, petrochemical plants, power plants and many other municipal utilities. The increasing statistics of various incidents and attacks occurred to these facilities clearly indicates the vulnerability of these strategic installations under the effects of intentional (terrorist) blasts. Therefore, Given the strategic nature of the care and maintenance for these tanks, their damage assessment under the prescribed explosion is quite important. Due to flammable content of some of these tanks, it is necessary to speed up the process of their vulnerability assessment and making the appropriate decisions for any needed...
A Knowledge Oriented Framework to Enable New Service Development Using Axiomatic Design Theory: Focusing on Hotel Business Models
, M.Sc. Thesis Sharif University of Technology ; Fattahi Valilai, Omid (Supervisor)
Abstract
In this research, the concept of new service development for Hotel industry is considered. As the concept of new service development encounters both business model structures and the required analysis for validation, the thesis has used the axiomatic design theory to evaluate the required service elements. Axiomatic Design framework as a scientific base for every type of design consists of 4 domains. The first domain named customer domain is the starting point at this research. In order to be prepared for applying in a real case study, customer domain is investigated and analyzed through a business model Canvas with nine building blocks covering all necessary and effective domains in a...
H 2 adsorption mechanism in Mg modified multi-walled carbon nanotubes for hydrogen storage
, Article International Journal of Hydrogen Energy ; Volume 37, Issue 2 , January , 2012 , Pages 1919-1926 ; 03603199 (ISSN) ; Mortazavi, S. Z ; Mirershadi, S ; Golikand, A. N ; Moshfegh, A. Z ; Sharif University of Technology
2012
Abstract
Multi-walled carbon nanotubes (MWCNTs) with diameter of about 50 nm were synthesized using thermal chemical vapor deposition. We have investigated the influence of Mg doping to the MWCNTs on its hydrogen storage property. TEM micrographs showed that Mg was attached to the MWCNTs and discontinuous arrangement of the carbon walls was recognized in the MWCNTs. According to XPS and BET analyses, the surface functional groups and pore size of the Mg-MWCNTs are increased by interactions between the Mg and the MWCNT's outer walls. The electrochemical discharging curves of the MWCNTs and Mg-doped MWCNTs revealed that the hydrogen storage capacity was 363 and 450 mAhg -1, respectively. Volumetric...
The effect of various acids treatment on the purification and electrochemical hydrogen storage of multi-walled carbon nanotubes
, Article Journal of Power Sources ; Volume 183, Issue 2 , 1 September , 2008 , Pages 539-543 ; 03787753 (ISSN) ; Mortazavi, S. Z ; Nozad Golikand, A ; Moshfegh, A. Z ; Mirershadi, S ; Sharif University of Technology
Elsevier
2008
Abstract
The effects of HCl, HNO3, H2SO4 and HF acids on the purification and the electrochemical hydrogen storage of multi-walled carbon nanotubes (MWCNTs) were studied. The MWCNTs were synthesized on Fe-Ni catalyst by thermal chemical vapor deposition method. The X-ray diffraction and thermal gravimetric analysis results indicated that the MWCNTs purified by HF acid had the highest impurities as compared with the other acids. The N2 adsorption results at 77 K indicated that all the samples were mainly mesoporous and the purified MWCNTs by HF acid had the highest surface area as compared with the other acids. The hydrogen storage capacities of the purified MWCNTs by the following acids were in...
Numerical Modeling of Diagnostic Fracture Injection Test
, M.Sc. Thesis Sharif University of Technology ; Shad, Saeed (Supervisor) ; Zivar, Davood (Co-Supervisor)
Abstract
Diagnostic Fracture Injection Test (DFIT) uses to identify the characteristics of the reservoir, including minimum horizontal stress, permeability, initial reservoir pressure, etc. The general steps of this process include fluid injection, fracture initiation in the matrix, fracture propagation and its closure due to fluid leak-off. The results of DFIT are analyzed in two stages based on the fracture closure event. The objective of this study is to investigate the effect of leak-off mechanisms on pressure-dependent leak-off (PDL), tip extension and fracture storage. To do so, different methods are used for identifying the cooperating parameters at each step. In order to analyze DFIT, a...
Multifunctional Ag/AgCl/ZnTiO3 structures as highly efficient photocatalysts for the removal of nitrophenols, CO2 photoreduction, biomedical waste treatment, and bacteria inactivation
, Article Applied Catalysis A: General ; Volume 643 , 2022 ; 0926860X (ISSN) ; Ghasemi, S ; Hajiahmadi, S ; Rhimi, B ; Nejad, Z. G ; Karima, S ; Shahsavari, Z ; Wang, C ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Over the past few decades, biological hazards and organic pollution have become major environmental concerns. Photocatalysis has been found to be effective in minimizing the negative impacts of these issues in air and water. Lozenge shape Ag/AgCl/ZnTiO3 photocatalysts were fabricated by a facile two-step synthesis method, including hydrothermal and coprecipitation. The physicochemical characteristics and morphological properties of the structures were comprehensively described taking advantage of a multi-technique approach. The prepared photocatalysts offered excellent nitrophenol mineralization (>90%) after 90 min of visible light irradiation. Based on the spin-trapping ESR technique, •O2̅–...
Hydrogen storage in decorated multiwalled carbon nanotubes by Ca, Co, Fe, Ni, and Pd nanoparticles under ambient conditions
, Article Journal of Physical Chemistry C ; Volume 115, Issue 14 , 2011 , Pages 6994-7001 ; 19327447 (ISSN) ; Mortazavi, S. Z ; Mirershadi, S ; Moshfegh, A. Z ; Parvin, P ; Golikand, A. N ; Sharif University of Technology
2011
Abstract
We report a study on hydrogen storage in Ca, Co, Fe, Ni, and Pd decorated multiwalled carbon nanotubes (MWCNTs) by using two techniques: volumetric and electrochemical. The results showed that hydrogen molecules are adsorbed on the defect sites and transported to the spaces between adjacent carbon via diffusion through both defect sites and opened tips into the layers. Hydrogen storage capacity can be improved in the decorated MWCNT by Co, Fe, Ni, and Ca metals in two approaches: (i) H2 adsorption via Kubas interaction and (ii) dissociation of H2 molecules on the metal particles. The results reveal that Pd are more effective catalyst for hydrogen storage process. It was found that...
Second order stress gradient plasticity with an application to thin foil bending
, Article International Journal of Mechanics and Materials in Design ; Volume 13, Issue 2 , 2017 , Pages 321-334 ; 15691713 (ISSN) ; Shishvan, S. S ; Zamani, Z ; Sharif University of Technology
Springer Netherlands
2017
Abstract
The continuum theory of dislocations is applied to formulate the problem of a double ended dislocation pileup under quadratic applied stress. Accordingly, a second order stress gradient plasticity model is presented to address the contribution of the first and the second stress gradients in the effect interpretation. The model is employed to predict the initial strengthening and subsequent hardening in curved and straight thin foils under pure bending within the continuum framework. It is shown that the so-called stress gradient plasticity model that ignores the second stress gradient may not give sound interpretations of the size effects. The plastic response of thin foils is affected by...
The role of energy subsidy reform in energy efficiency enhancement: lessons learnt and future potential for iranian industries
, Article Journal of Cleaner Production ; Volume 197 , 2018 , Pages 542-550 ; 09596526 (ISSN) ; Fakouriyan, S ; Sheykhha, S ; Sharif University of Technology
2018
Abstract
Significant energy subsidies are believed to be the main factor that has resulted in high energy intensities of Iranian industries. The Subsidy Reform Act of 2010 was directed at modifying energy consumption pattern and fostering energy efficiency enhancement. This study aims at analyzing the effect of energy subsidy reform on promoting energy efficiency in six energy intensive industries of Iran. In order to do so, the energy efficiency practices that have not been adopted after the implementation of the first phase of energy subsidy reform are investigated. Data analysis reveals that if financially interesting investments are determined as those with payback periods less than three years,...
Delafossite-alumina nanocomposite for enhanced catalytic wet peroxide oxidation of anionic pollutants
, Article Journal of Hazardous Materials ; Volume 417 , 2021 ; 03043894 (ISSN) ; Nouri, O ; Xie, Z ; Setayesh, S. R ; Wei, Z ; Sharif University of Technology
Elsevier B.V
2021
Abstract
Mass transfer efficiency and catalytic reactivity are the two major hurdles for heterogeneous catalytic wet peroxide oxidation (CWPO) technologies. To address these issues, nanocomposite CuFeO2/Al2O3 was synthesized and assessed as a novel catalyst for enhanced adsorption and oxidation of anionic pollutants (catechol and reactive red 195 (RR195)) in waters. With a positive charge on the nanocomposite by introducing Al2O3, the adsorption of anionic pollutants was promoted. The surface complexation reaction on CuFeO2/Al2O3, which fits well to the Langmuir isotherm, has engined the mass transfer of pollutants to the nanocatalyst that demonstrated 96.46% and 99.75% removal of catechol and RR195...
Unified modeling and experimental realization of electrical and thermal percolation in polymer composites
, Article Applied Physics Reviews ; Volume 9, Issue 4 , 2022 ; 19319401 (ISSN) ; Arabshahi, Z. S ; Saberi, A. A ; Moshfegh, A. Z ; Sharif University of Technology
American Institute of Physics Inc
2022
Abstract
Correlations between electrical and thermal conduction in polymer composites are blurred due to the complex contribution of charge and heat carriers at the nanoscale junctions of filler particles. Conflicting reports on the lack or existence of thermal percolation in polymer composites have made it the subject of great controversy for decades. Here, we develop a generalized percolation framework that describes both electrical and thermal conductivity within a remarkably wide range of filler-to-matrix conductivity ratios (Y f / Y m), covering 20 orders of magnitude. Our unified theory provides a genuine classification of electrical conductivity with typical Y f / Y m ≥ 10 10 as...
Kinetic parameters estimation of MgO-C refractory by shrinking core model
, Article Journal of Materials Science and Technology ; Volume 22, Issue 6 , 2006 , Pages 826-832 ; 10050302 (ISSN) ; Nemati, Z. A ; Sadrnezhaad, S. K ; Moghimi, Z. A ; Sharif University of Technology
2006
Abstract
Kinetics of oxidation of MgO-C refractories was investigated by shrinking core modeling of the gas-solid reactions taking place during heating the porous materials to the high temperatures. Samples containing 4.5-17 wt pct graphite were isothermally oxidized at 1000-1350°C. Weight loss data was compared with predictions of the model. A mixed 2-stage mechanism comprised of pore diffusion plus boundary layer gas transfer was shown to generally control the oxidation rate. Pore diffusion was however more effective, especially at graphite contents lower than 10 wt pct under forced convection blowing of the air. Model calculations showed that effective gas diffusion coefficients were in the range...