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Use of Data Assimilation Methods for Multiphase Flow in Porous Media
, M.Sc. Thesis Sharif University of Technology ; Rajabi Ghahnavieh, Abbas (Supervisor) ; Bazargan, Hamid (Co-Supervisor)
Abstract
The importance of optimizing the extraction process of available resources increases each day due to the increasing energy consumption and the lack of energy resources. Oil and gas are one of the most important sources of energy. Although existing oil and gas resources are thought to be sufficient to meet the growing energy demand for the next few decades, given the non-renewable nature of these resources and the growing demand for oil and gas, it will become much harder to meet the future energy demand. Many existing oil fields are now in the process of maturing, and the discovery of large new oil fields is rare. As a result, new technologies must be used in the future to meet this demand,...
Meta-Heuristic Algorithm for Minimization of Total Tardiness in Flexible Flow Shop Scheduling Problems
, M.Sc. Thesis Sharif University of Technology ; Salmasi, Nasser (Supervisor) ; Shavandi, Hassan (Co-Supervisor) ; Najafi, Amir Abbas (Co-Supervisor)
Abstract
This study deals with the heuristic solution of flexible flow shop scheduling problems with unrelated parallel machines. No preemption of jobs is allowed. As an objective function, this paper considers the minimization of total tardiness. As a first step to propose solution, two different mixed integer mathematical models are developed which tackle the problem at hand. The problem is NP-hard and thus the developed mathematical program can only solve problem instances for small sizes in a reasonable amount of time. The next step is to build heuristics which can provide feasible solutions in polynomial time for larger problem instances. Then in the study develops a constructive heuristic for...
Multi-level decomposition approach for problem solving and design in software engineering
, Article Proceedings of the Annual Southeast Conference, 24 March 2011 through 26 March 2011 ; March , 2011 , Pages 249-254 ; 9781450306867 (ISBN) ; Niu, N ; Najafi, F ; Sharif University of Technology
2011
Abstract
In general, decomposition methods can facilitate the process of solving sophisticated and heterogonous problems in the area of software development and engineering. These approaches are assisting to decompose problems based on different disciplines, characteristics and functionalities that is results into increasing the computational efficiency (e.g. parallel processing/computing) and accelerate the software changing process, software modifications and error tracking. Essentially, these approaches contribute to the degree of modularity to decompose a complex problem into different sub-problems and to focus on local objectives. There are different approaches that are used to decompose a...
A mathematical analysis of the mechanism of ultrasonic induced fluid percolation in porous media: Part I
, Article Proceedings - SPE Annual Technical Conference and Exhibition, 20 September 2010 through 22 September 2010 ; Volume 7 , September , 2010 , Pages 5833-5856 ; 9781617389641 (ISBN) ; Sharif University of Technology
2010
Abstract
This work concerns with experimentally and analytically investigation of free gravity drainage process in porous media under the influence of ultrasonic wave radiation. Glass beads ranges from 70 to 100 mesh sizes were packed and used in the tests. The working fluids consist of distilled water, kerosene and Doroud and Paidar crude oils as wetting and air as non-wetting phase. The measured oil recovery data along with Hagoort (1984) backward methodology were used to determine and to compare the relative permeability of wetting phases in presence and absence of ultrasonic radiation. In addition the relative permeability of non-wetting phases for both cases were calculated from inverse modeling...
High Saline Water Treatment by the Process of Membrane Distillation Combined with Solar Energy
, M.Sc. Thesis Sharif University of Technology ; Rajabi, Abbas (Supervisor) ; Musavi, Abbas (Supervisor)
Abstract
In this study, membrane distillation process was used for treatment of high salinity waters. The focus of this study is to simulate and build a setup of membrane distillation process. Since the membrane distillation process is based on the driving force of the temperature difference, the required temperature is provided by both the use of heaters and the use of solar energy. To increase the feed temperature by solar energy, a black polymer coating on the main membrane is used. The main membrane used in this process is PVDF polymer and the polymer coated on the surface is the PAN polymer. After simulating and constructing the laboratory setup, the influence of a variety of parameters on the...
Development of sol-gel-derived multi-wall carbon nanotube/hydroxyapatite nanocomposite powders for bone substitution
, Article Journal of Composite Materials ; Vol. 48, issue. 4 , February , 2014 , pp. 483-489 ; ISSN: 00219983 ; Abrishamchian, A ; Najafi, F ; Mohammadi, M ; Najafi, H ; Tahriri, M ; Sharif University of Technology
2014
Abstract
Carbon nanotubes with unique physical and mechanical properties have shown great potential for biological applications, including tissue engineering and mimicking the structure and properties of human bones. In the present work, sol-gel synthesized nanocomposite powder of multi-wall carbon nanotube/hydroxyapatite characterized using field-emission scanning electron microscopy, transmission electron microscope, X-ray diffraction, Fourier transform infra-red spectroscopy and thermal analyses. The results show homogenous dispersion of nanotube in well-crystallized hydroxyapatite ceramic matrix. Scanning electron microscopy and transmission electron microscope observations show the sodium...
Evaluation of relationship among filler amount, degree of conversion, and cytotoxicity: approaching performance enhancement novel design for dental Bis-GMA/UDMA/TEGDMA composite
, Article International Journal of Polymeric Materials and Polymeric Biomaterials ; Volume 66, Issue 16 , 2017 , Pages 844-852 ; 00914037 (ISSN) ; Akbari, B ; Najafi, F ; Abrishamkar, A ; Ramedani, A ; Yazdanpanah, A ; Sharif University of Technology
2017
Abstract
Dental composites of A2 color using Bis-GMA, urethane dimethacrylate and triethyleneglycol dimethycrylate resins (70/20/10), and silica filler (70 wt%, 75 wt%, and 80 wt%), a hybrid of nano- and microsilica particles, are made and subjected to the following tests: Fourier transform infrared spectroscopy (FTIR), particle size analyzer, scanning electron microscope (SEM), and also cytotoxicity. FTIR results show that an increase in filler amount yields to a decrease in degree of conversion. Therefore, there should be a compromise between degree of conversion and the filler amount. SEM images manifest the uniformity of silica particles. It is shown from the cytotoxicity tests that as the...
A Multi-Objective Robust Optimization Model for Logistics Planning in the Earthquake Response Phase [electronic resource]
, Article Transportation Research Part E: Logistics and Transportation Review, Elsevier ; Volume 49, Issue 1, January 2013, , Pages 217–249 ; Eshghi, Kourosh ; Dullaert, Wout ; Sharif University of Technology
Abstract
Usually, resources are short in supply when earthquakes occur. In such emergency situations, disaster relief organizations must use these scarce resources efficiently to achieve the best possible emergency relief. This paper therefore proposes a multi-objective, multi-mode, multi-commodity, and multi-period stochastic model to manage the logistics of both commodities and injured people in the earthquake response. Also, a robust approach is developed and used to make sure that the distribution plan performs well under the various situations that can follow an earthquake. Afterwards, it proposes a solution methodology according to hierarchical objective functions and uses it to illustrate the...
Modeling and Predictive Control of Vinyl Acetate Polymerization in Semi-batch Reactor
, M.Sc. Thesis Sharif University of Technology ; Shahrokhi, Mohammad (Supervisor)
Abstract
Obtaining polymers with desired properties is very important from industrial point of view. Weight average molecular weight and polydispersity are two important polymer properties. It is also important to obtain a high monomer conversion. In this thesis production of polyvinyl acetate is considered. Under special conditions, the vinyl acetate reactor dynamics become oscillatory which makes the reactor control difficult. For obtaining polymer with desired properties, an objective function which includes weight average molecular weight, polydispersity and monomer conversion has been defined. Then by minimizing this objective function the optimal temperature trajectory is obtained. In this...
Web Driven Alert Correlation
, M.Sc. Thesis Sharif University of Technology ; Jalili, Rasoul (Supervisor)
Abstract
With the growing deployment of host and network intrusion detection systems, analyzing generated alerts from these systems becomes critically important and challenging due to its complexity and high amount of data. A perfect intrusion detection system would be able to identify all the attacks without raising any false and non-relevant alarms. Unfortunately, false alarms are commonplace in intrusion detection systems. Non-relevant alerts, which are associated with attacks that were not successful, are also common. The process of identifying false and non-relevant alerts is called alert verification. Also nowadays, web applications are widely used in critical and important roles (e.g.,...
An Approach to Optimize Resource Allocation and Strategies to Control Infectious Diseases
, M.Sc. Thesis Sharif University of Technology ; Najafi, Mehdi (Supervisor)
Abstract
Infectious diseases have always been a threat to mankind, and is the greatest causes of death of children and young people. Although this type of diseases is a serious threat to public health; the allocated resources in responding to a semi-large pandemic is inadequate. Therefore, it is important to spend the resources in the most effective and efficient ways to improve pandemic response capability. That is why considerable research be devoted to study different aspects of epidemics, and developed mathematical approaches to choose appropriate strategies in pandemic response. Since the epidemic models are simplified means to describe the transmission of disease, researchers often use these...
Designing a Mathematical Model for Optimizing Organ Transplant Network
, M.Sc. Thesis Sharif University of Technology ; Najafi, Mehdi (Supervisor)
Abstract
Presently, numerous patients die each day while they are awaiting life-saving organ transplant. Despite advances in medicine and technology, and increased awareness of organ donation and transplantation, the gap between supply and demand continues to widen. Therefore, appropriate utilization of donated organs under organ allocation process is vital, and can save several patients’ life. Due to this cause, this study presents a mixed integer multi-period mathematical model to optimize allocation system in an organ transplantation network. The considered network includes donors, hospitals, procurement centers, transplant centers, and patients. The proposed model strives to minimize the overall...
Blood Inventory Management in Hospitals: Considering the Uncertainty
of Supply, Demand and Blood Transshipment
,
M.Sc. Thesis
Sharif University of Technology
;
Najafi, Mehdi
(Supervisor)
Abstract
In recent years there is a growing trend in designing efficient health care systems. The applications of operations research have been instrumental in advancing this growing trend too. The blood management issue has raised concerns for human on the other hand. Blood is one of the vital commodities in the field of health. Despite significant advances in the field of medicine, a suitable replacement for this vital commodity has not been found yet. Collecting and managing the distribution of blood that is discussed in the blood supply chain management, requires careful planning and managing. In this research blood inventory management in hospitals considering the uncertainty of supply, demand...
Enhancing Privacy in Location-Based Services
, M.Sc. Thesis Sharif University of Technology ; Jalili, Rasool (Supervisor)
Abstract
Mobile localization development, is the reason for appearance of location-based services (LBS). Be sure of not disclosing the user personal information is the main challenge in LBS. Many different concepts and approaches for the protection of location privacy have been described in the literature which change the query of user to server. These approaches falling roughly into two main categories: centralized and distributed (user-centric). Centralized category includes approaches like “changing query pattern” using encryption on user device, or using an “anonymizer trusted third party”. In such approaches threat of an untrustworthy LBS server is addressed by the introduction of a new...
A Model to Schedule Hospital Nurses Considering Nurses Preferences
, M.Sc. Thesis Sharif University of Technology ; Najafi, Mehdi (Supervisor)
Abstract
The nurse scheduling problem is an inevitable issue in managing of hospital wards. Maintaining high quality of working in hospitals is too difficult in tense and high-pressure work environment. Manually solving the scheduling problem is time-consuming. It can pose problems to considering individual excellence, personnel requests and distributing shifts in a fair and desirable manner. These problems and the impossibility of considering all conditions together made the nurse scheduling as an important scheduling problem. In this research we propose a model to assign nurses to shifts considering regulations and hospital’s policies. Unlike nurse scheduling literature we consider nurses...
Developing a Continuous Location Routing Model and Providing a Hybrid Algorithm Based on Automatic Clustering
, M.Sc. Thesis Sharif University of Technology ; Najafi, Mehdi (Supervisor)
Abstract
Generally, the costs of logistics and distribution are included in the significant share of the product price. Hence, choosing appropriate decisions and reducing these costs can have an important effect in reducing the price of products and services, increasing the competitiveness of enterprises. One of the most important measures, in order to achieve this goal, is to integrate location of distribution centers and the routing paths of goods. That how these decisions are made in the networks and discrete problems seriously has been taken into consideration but in continuous areas due to the complexity has not been studied a lot by scholars. In this study, we try to develop a model for...
Maximum Flow Network Interdiction Problem in Drug Supply Chain
, M.Sc. Thesis Sharif University of Technology ; Najafi, Mahdi (Supervisor)
Abstract
Given the great importance and urgency of preventive operation against illegal drug trafficking as a social scourge, it is necessary to schedule and optimize the police decision in order to interdict further distribution of this harmful product. In this thesis, we study interdiction of drug distribution as multi-period maximum flow profit network interdiction on a multi-commodity flow and multi-source-sink network. The drug distribution network consists of criminal who are dynamically connected and seek to maximize the total flow profit from sources to sinks while the police aim to reduce aim to reduce total flow profit over long period of time by monitoring and interdicting criminals due to...
An Approach to Optimize Beam Angles and Fluence Map in IMRT
, M.Sc. Thesis Sharif University of Technology ; Najafi, Mehdi (Supervisor)
Abstract
Intensity Modulated Radiation Therapy is one of the most commonly used procedures of delivering radiation to cancerous tissues, with the aim of reaching the prescripted dose in the target volume while minimizing damage to nearby healthy organs. Two decisions are of fundamental importance: to select the beam angles and calculate the beam intensities. Beam Angle selection (Beam Angle Optimization) is an important problem. Due to the large amounts of computational time, beam angles are often selected manually based on human experience and intuition. In this study, three optimization methods –Simulated Annealing, Branch & Prune and Local Neighborhood Search- that are selected among known methods...
Simulation of Heat and Mass Balance in Rotary Kiln of Iron Pellets Induration
, M.Sc. Thesis Sharif University of Technology ; Yuzbashizadeh, Hossein (Supervisor)
Abstract
In this study, the heat and mass balance of rotary kiln of iron pellets induration was simulated. Due to large amount of heat transfer calculations, a quasi three-dimensional model has been used in this study. First, the freeboard heat condition was simulated via fluent program and the average temperature of freeboard was stablished. Then, a one-dimensional heat transfer model was developed using heat transfer equations. In this model, the heat transfer via conduction, convection and radiation in different parts of the kiln was included. Also, the bed reactions and their effect on bed temperature were evaluated. Finally, transversal movement and velocity of particles was studied. Transversal...
A Mathematical Model to Make Decision in a Combinatorial Reverse Auction Considering Lack of Supply Risk
, M.Sc. Thesis Sharif University of Technology ; Najafi, Mehdi (Supervisor)
Abstract
Considering the increased variety of products or services demanded by customers, the lifetime of the products or services demanded has been shortened. So, organizations should provide the products or services they need in the shortest possible time. That is why to survive in the competitive environment created, many organizations provide the products or services they need from outside the organization to meet their customers' demand in the shortest time. One of the ways by which various products or services can be provided is to hold combinatorial reverse auctions. Following a comprehensive review of the literature related to the combinatorial reverse auctions, this study has presented a...