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Application of Damage Indices In Seismic Analysis of Concrete Frames Using Endurance Time Method
, M.Sc. Thesis Sharif University of Technology ; Esmaeil Pourestekanchi, Homayoun (Supervisor)
Abstract
In most places in the world as it is in our country, structural vibration caused by earthquakes are among the most destructive menaces for the building. For this reason one of the main goals for civil engineers is constructing structures that can perform properly in an earthquake-exposed situation. For moving toward this goal it is necessary to estimate structural responses considering probable earthquake excitation and use these data for design of new structures or retrofitting of existing ones. In this research, the capability of a new method named Endurance Time analysis in seismic assessment of concrete moment frame is investigated in nonlinear range. ET is a new dynamic time history...
Performance-Based Design of Steel Structures with Metallic damper Using Endurance Time Method
, M.Sc. Thesis Sharif University of Technology ; Esmaeil Pourestekanchi, Homayoun (Supervisor)
Abstract
Preventing critical damages to structures and hence saving the lives and money is an inevitable work which a designer has to do. During the earthquake, huge amount of energy applies to the structure and finding a way to reduce transfer of this energy to main structure is crucial. For this purpose, Structural Control systems may be used. Metallic Dampers are one of those systems which absorb the earthquake input energy by having nonlinear deformations. In this Thesis, one type of this dampers which is innovated by Estekanchi, have been studied .Indeed, this damper is a connection between bracing and main frame. In this damper a U shape part acts as a sacrificing portion and absorbs energy by...
Seismic Performance and Cost Assessment of Concrete Bridges Designed by Iranian Bridge Code
, M.Sc. Thesis Sharif University of Technology ; Esmaeil Purestekanchi, Homayoun (Supervisor)
Abstract
The purpose of this study is to evaluate the performance and seismic costs for pre-designed bridges according to the Iranian Bridge Code, which maps and details are available in Code 294. In order to evaluate performance, seismic costs of a structures are determined over its life cycle and these costs are compared eventually. Seismic costs are divided into two parts of the initial cost and life cycle cost of the structure. The initial costs depend on the cost of constructing the bridge, but life cycle costs are depends on seismic damage for structure and its users over the useful life of the bridge. These damages include the cost of maintenance of the bridge over its useful life and the...
Seismic Analysis of Elevated Concrete Tanks with Endurance Time Method
, M.Sc. Thesis Sharif University of Technology ; Esmaeil Poorestekanchi, Homayoun (Supervisor)
Abstract
Elevated concrete tanks have a wide range of applications in storing drinking water, firefighting, sewage, oil, toxic chemicals, and similar fluids. Therefore, due to their usage, these tanks are usually placed in the category of very important structures and vital arteries. Consequently, their design against seismic loads and their proper performance during earthquakes are of great importance. The endeavor time Analysis is a seismic analysis method in which the structure is subjected to an increasing dynamic excitation whose intensity gradually increases over time. The structure's response over time is examined, and based on the corresponding response to various levels of excitation...
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...
Information-Theoretic Analysis of Coognitive Radio Networks
, Ph.D. Dissertation Sharif University of Technology ; Hashemi, Homayoun (Supervisor) ; Nasiri Kenari, Masoumeh (Supervisor)
Abstract
In this thesis, the effect of cognition in wireless networks is studied. In a wireless communica-tion network, cognition is the ability of a device to sense the transmissions of neighboring nodes and adapt its own transmission to the sensed environment. Cognitive radios are very attractive be-cause of the increasing need for more efficient use of frequency spectrum. The goal of this thesis is the analysis of cognitive radio networks from an information theoretic perspective and to this end statistical models of the wireless medium with a limited and tractable number of devices are uti-lized. We consider three different models in three parts of the thesis. First, we consider a new...
A Front-End for an Integrated UHF RFID Reader
, M.Sc. Thesis Sharif University of Technology ; Sharif Bakhtiar, Mehrdad (Supervisor) ; Atarodi, Mojtaba (Supervisor)
Abstract
The use of Radio Frequency Identification is increasing rapidly. The reason is the capability to transfer data wirelessly without line-of-sight necessity, high data rate and long read range. The main advantage of barcode is its lower cost which has ensured its existence for many years. The applications and materials that are identified by RFID increase as the price of RFID tags decrease. This Project deals with the front-end of an Integrated RFID Reader for the UHF band. The bottleneck of the design is the presence of a large interferer just hundreds of kilohertz apart from the desired signal which is at about 900 MHz. The key idea of the design is utilizing feedback in order to cancel...
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...
Dynamics of a Viscoelastic Plate on a Viscoelastic Foundation Subjected to a Moving Mass
, Ph.D. Dissertation Sharif University of Technology ; Esmaeil Purestekanchi, Homayoun (Supervisor) ; Mofid, Masoud (Co-Advisor)
Abstract
This thesis investigates the dynamic response of a viscoelastic plate resting on a viscoelastic Winkler foundation subjected to the excitation of a moving mass. Through application of the Laplace transform, the governing equation of the problem is derived for a general viscoelastic material. Thereafter, an analytical-numerical method is proposed in order to determine the dynamic response of the viscoelastic plate. The method is based on transforming the governing partial differential equation into a new solvable system of linear ordinary differential equations. To that extent, the proposed solution proves to be applicable to plates made of any viscoelastic material and with various boundary...
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...
Numerical investigation of flow pattern and hydrodynamic forces of submerged marine propellers using unsteady boundary element method
, Article Proceedings of the Institution of Mechanical Engineers Part M: Journal of Engineering for the Maritime Environment ; Volume 233, Issue 1 , 2019 , Pages 67-79 ; 14750902 (ISSN) ; Abbaspoor, M ; Sharif University of Technology
SAGE Publications Ltd
2019
Abstract
In this study, a numerical model of unsteady potential flow around submerged marine propellers has been developed. The boundary element approach in combination with time stepping method to model free wake dynamics has been implemented. An important feature of this method in the simulation of pressure-dominant problems is a proper balance between time and accuracy in the numerical process. Another advantage of time stepping method is that there is no need to define wake geometry before modeling. Due to inherent instability of boundary integral equations, a smoothing function to damp the effect of singularities is imposed to the solution. The main innovative idea of this work is that the...
Numerical study of propulsion performance in swimming fish using boundary element method
, Article Journal of the Brazilian Society of Mechanical Sciences and Engineering ; Volume 39, Issue 2 , 2017 , Pages 443-455 ; 16785878 (ISSN) ; Abbaspour, M ; Sharif University of Technology
Springer Verlag
2017
Abstract
In this paper, hydrodynamic simulation of fish-like swimming for two types of aquatic animals including tuna fish and giant danio is presented. We employ an unsteady three-dimensional inviscid boundary element method including time stepping algorithm to capture the wake sheet and flow features around swimming fish in a straight course. At each time step, an unsteady Bernoulli equation was used to find the pressure distribution and thrust generated by the animal. To couple fluid solver with kinematic equations of flexible body, undulating motions of backbone were defined using a prescribed continuous function. Although the flexible motion mechanism controls the fish swimming but no structural...
Pricing and quality setting strategy in maritime transportation: Considering empty repositioning and demand uncertainty
, Article International Journal of Production Economics ; Volume 240 , 2021 ; 09255273 (ISSN) ; Zolfagharinia, H ; Sharif University of Technology
Elsevier B.V
2021
Abstract
Imbalanced international trade and the limited number of containers in the maritime transportation industry have resulted in considerable costs and decreased profits for shipping firms. To manage these issues, this study utilizes price management techniques to control empty container repositioning in a transportation system. In this system, there is a firm providing transportation services between two ports in both directions. Each direction has its own uncertain potential demand that can be affected by the prices and the quality set by the firm. We develop a mathematical formulation to set the quality and prices of the service in order to maximize the firm's profit. Due to demand...
Strain hardening mechanisms in aged AEREX350 superalloy
, Article Materials Science and Engineering A ; Volume 398, Issue 1-2 , 2005 , Pages 204-208 ; 09215093 (ISSN) ; Asgari, S ; Sharif University of Technology
2005
Abstract
In this paper, results of an investigation on strain hardening mechanisms of aged AEREX350 alloy during room temperature compression testing are reported. TEM studies were conducted on commercial samples aged at 850 °C both before and after deformation in a strain range of 0.15-0.27. It was found that only coherent γ′ precipitates with L12 structure formed in these samples prior to deformation. TEM studies also showed twin intersections in the deformed samples. Based on these observations, it is suggested that the high strain hardening rate of the aged material in this strain range is mainly related to the formation of intersecting deformation twins. This is attributed to the decrease in 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...
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...
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...
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...