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jafari-najafi--niloofar
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Study of Invariants of Diophantine Forms and Equations
, M.Sc. Thesis Sharif University of Technology ; Jafari, Amir (Supervisor)
Abstract
The aim of this thesis is to study invariants of Diophantine forms and equations. These invariants are the transformations that do not change the original equations and forms. This thesis has a different view to the concept of invariants from Hlibertian view. Based on this new definition, by having one of the solutions of the equation, new solutions can be found with invariant method. The number of these solutions can be finite or infinite. In case of infinite solutions this method is more important. The focus of this thesis is on forms and linear invariants. The most important result in this text is about two main theorems that can classify the invariants of all completely decomposable...
Finding Invariants and Parametric Solutions for Some Systems of Diophantine Equations with Arbitrary Coefficients and Variables Over Q
, Ph.D. Dissertation Sharif University of Technology ; Jafari, Amir (Supervisor)
Abstract
The main topic of this dissertation is to find methods for obtaining parametric solutions and linear/nonlinear invariants of Diophantine equations and consists of 4 chapters. The first chapter consists of some introductory discussions. The second chapter begins with a review of linear invariant, U-invariants, covariants and the concept of semi-invariants. The generators of maximum degree 3 for producing all linear invariants are introduced in Chapter 2 as well. Moreover, the relations between 3rd and 4th degree Hilbert invariants in terms of Procesi bases are included in this chapter.In chapter 3, a general conjecture is given to check whether there are finitely many solutions to a...
Flow Simulation to Assess Effects of Various Parameters on Performance of a Gas Ultrasonic Flowmeter
, M.Sc. Thesis Sharif University of Technology ; Mazaheri, Karim (Supervisor)
Abstract
In this thesis we are going to improve an ultrasonic flowmeter accuracy by considering the influence of different parameters like temperature, pressure, etc. Firstl of all different cases of flow condition in which ultrasonic flowmeter may work are specified, then velocity and temperature profile of pipe flow are determined using Fluent software. In thr next step ultrasonic pulses transmitted are simulated by the use of code written in Matlab to find wave travel time in the flow. Evetually an accurate relation of calibration for flowmeter is determined by the use of travel time and all other flow properties to evaluate the accuracy of flowmeter in diffent cases. Relation extracted can be...
Optimization of Combination Chemotherapy Problem with Uncertain Cell Cxycle
, M.Sc. Thesis Sharif University of Technology ; Rafiee, Majid (Supervisor) ; Najafi, Mehdi (Supervisor)
Abstract
Nowadays, chemotherapy is one of the common ways to treat cancer. Although, chemotherapy is used to kill cancer cells , chemotherapy drugs also target healthy cells and tissues of the body. In practice, it is difficult to strike a balance between injectable doses of drugs and toxicity in the body, and physicians are always looking for an effective treatment plan. One of the most common drugs that physicians use in chemotherapy is cell-cycle-specific drugs. These types of chemotherapy drugs affect only a certain phase of cell cycle and to a certain extent. Since the lifetime of the cancer cells is uncertain, the effective use of these drugs depends on the correct injection time of the drugs...
Enhanced Performance of Modified Pd/AL2O3 Catalysts by Triphenyl phosphine Ligand in Acetylene Selective Hydrogenation
, M.Sc. Thesis Sharif University of Technology ; Khorasheh, Farhad (Supervisor) ; Takht Ravanchi, Maryam (Supervisor)
Abstract
Ethylene is considered as one of the key materials in the petrochemical industry and has a particular importance. Polymerized ethylene produces polyethylene, which is widely used in plastics and pipe-manufacturing industries. Ethylene is mainly produced by the processes of catalytic cracking or thermal cracking of heavier hydrocarbon compounds. In these processes, acetylene is produced as a by-product, which deactivates the Ziegler-Nata catalysts in the polymerization unit of ethylene. Therefore, there should be some considerations to reduce acetylene to its minimum value -around zero. For this purpose, the fixed bed catalytic reactor is used to hydrogenate acetylene to ethylene. Various...
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...
High-performance carboxylate superplasticizers for concretes: Interplay between the polymerization temperature and properties
, Article Journal of Applied Polymer Science ; Volume 134, Issue 23 , 2017 ; 00218995 (ISSN) ; Saeb, M. R ; Jafari, S. H ; Najafi, F ; Khonakdar, H. A ; Ayoubi, M ; Hassanpour Asl, F ; Sharif University of Technology
2017
Abstract
Polycarboxylate superplasticizers based on acrylic acid (AA) and maleic anhydride (MAn) were synthesized via free-radical copolymerization with an ethylene glycol monomer and characterized. The copolymerization temperature (ranging from 50 to 90 °C) appeared to be the key operating factor governing the chemical structure of the superplasticizers. The chemical structures of the products were analyzed by gel permeation chromatography, whereas an optimized sample was further analyzed by Fourier transform infrared spectroscopy and 1H-NMR. Superplasticizers of the AA and MAn classes were then incorporated into concrete, and their performances were measured by slump and slump loss tests, where a...
A full pipeline of diagnosis and prognosis the risk of chronic diseases using deep learning and Shapley values: The Ravansar county anthropometric cohort study
, Article PLoS ONE ; Volume 17, Issue 1 January , 2022 ; 19326203 (ISSN) ; Shohaimi, S ; Salari, N ; Kiaei, A. A ; Najafi, F ; Khazaei, S ; Niaparast, M ; Abdollahi, A ; Mohammadi, M ; Sharif University of Technology
Public Library of Science
2022
Abstract
Anthropometry is a Greek word that consists of the two words "Anthropo"meaning human species and "metery"meaning measurement. It is a science that deals with the size of the body including the dimensions of different parts, the field of motion and the strength of the muscles of the body. Specific individual dimensions such as heights, widths, depths, distances, environments and curvatures are usually measured. In this article, we investigate the anthropometric characteristics of patients with chronic diseases (diabetes, hypertension, cardiovascular disease, heart attacks and strokes) and find the factors affecting these diseases and the extent of the impact of each to make the necessary...
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...
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...