Sharif Digital Repository

The railroad blocking problem emerges as an important issue at the tactical level of planning in freight rail transportation. This problem consists of determining the paths of each shipment which minimize the total cost subject to the key constraints such as limitation on travel time, limitation on number of dispatched trains, and limitation on the number of cars classified at each station. The multi-path railroad blocking model is developed and then a new heuristic algorithm based on the Lagrangian relaxation technique to solve the realistic rail network is introduced.To consider the uncertainty which is inherent in the demand and travel time (as a supply indicator of rail system), a... 

The purpose of this study is to find the conflicting assumptions of the main actors in the legislation process of Knowledge-based Act. Collecting and classifying all documents related to this policy process, and based on interviews with main actors involved in this process (with different objectives) and using thematic analysis, we first attempt to classify the main actors involved in the process. Second, we analyze the conflicting paradigms which have led to political conflicts in the process. This analysis helps to improve the policy process of similar acts in future  

Vortex-induced vibration is a known phenomenon in fluids flow that is being studied in different fields of engineering and usually, we want to reduce the harmful effects of this phenomenon on the subjected structures. Also, it is possible to use this phenomenon for harvesting clean energy from fluids flow. Energy harvesting from vortex-induced vibrations is based on the maximizing of flow instead of its reduction, and the utilization of these vibrations instead of their suppression. Vortex induced vibrations occur in any ranges of Reynolds numbers. Only in three transient regions cause a reduction in vortex-induced vibrations; therefore, even in streams with a velocity less than 0.2 m/s, it... 

In this study a droplet-based microfluidic system is desighned and fabricated to effectiverly lyse MCF7 cells and extract and purify their DNAs. The main purpose of this study is to transfer all the steps from macro scale to a microfluidic system containing a fluidic chip. This system is a semi automatic system and every part of the lysis and purification process is performed in one step. The first step is to encapsulate single cells and multi cells inside the droplets. By controlling the concentration of the cell solution, the number of encapsulated cells inside the droplet is efficiently and easily controlled and the cells were encapsulated as single cells and as multi cells inside the... 

Given that highly deformable natural deposits such as collapsible and swelling soils make up more than one-fifth of the land surface and are generally in unsaturated conditions, behavioral measurement of this type of soil including accurate measurement of its hydraulic properties is important. The challenges of designing and implementing construction infrastructure, along with the most reported financial losses due to the presence of these soils, double the importance of studying the behavior of these soils. The large volume changes of these soils in contact with water (equivalent to a volumetric strain of more than 5%) has been a major challenge for researchers in predicting the... 

One of the influential factors affecting the future price trends of a stock is the public sentiment surrounding that particular stock. In recent years, researchers have employed Natural Language Processing (NLP) techniques to analyze textual data present on social networks, aiming to investigate public opinions. However, there has been limited attention given to validating the users expressing opinions concerning the stock market. Much of the opinions shared on social networks lack a thorough examination and analysis of the market, often being solely based on the author's sentiments. This research endeavors to validate active users on the social network 'X' (Twitter) by developing a... 

Dehydrogenation of C10-C14 normal paraffins on Pt/alumina catalyst is a reaction of prime importance particularly to the detergent industry for the manufacture of the active ingredients. In this thesis, the modifying effect of Zn, Li, K, and Mg on the activity and selectivity of the Pt-Sn/γ-Al2O3 dehydrogenation catalysts were investigated. The catalysts were prepared by co-impregnation, characterized by TPR, BET, SEM, EDAX and XRD techniques and tested in a tubular reactor. Zinc reduced the activity of Pt-Sn alloy and hence reduced the catalyst activity in the dehydrogenation reaction and enhanced its selectivity to normal mono olefins. The addition of Li, K, and Mg to Pt-Sn/γ-Al2O3... 

Polycrystalline materials are solids that are composed of many crystallites of varying size and orientation called “Grain”. As the grain size reduces to the values below 100nm, the overall material properties are remarkably changed, and thus the resulting nanocrystalline materials have provided much better engineering properties at the same chemical composition compared to the microcrystalline. The main objective of the present study is to synthesize a nanocrystalline (22nm-25nm) coating based on Nickel over the yellow-brass plates. To do this, an electroplating technique in a modified Watts bath is employed in which the current density and stirring speed varied between 3 to 9.5 Ampere per... 

In this project, nonocrystalline zinc coatings with grain sizes within the range of 22-63 nanometers were produced on yellow-brass plates by electroplating in an acidic chloride bath in the presence and absence of additive has been investigated.current densities and bath stirring speeds change from 2 to 6 A/dm2 and 0 to 400 rpm respectively.To determine crystallite size, X-ray diffraction technique (XRD) was utilized;it was found that the use of additive has effectively refined the grain size and optimum current density is 3 A/dm2 to reach this objective.. it was observed that grain size increased continuously with increase in bath stirring speed. The results coming from XRD tests were... 

In this thesis, three new metallic-yielding dampers for dissipation of energy in structures are introduced and studied. The advantages of dissipation of energy from torsional yielding in comparison to tensile yielding is verified by performing both monotonic and cyclic tests on three aluminum alloys specimens and a mild steel specimen. The experiments confirm that the energy absorption of steel in torsion is much higher than that in tension. Three different mechanisms are introduced to transform the axial movement into the torsional rotation. Each mechanism is studied in details. The first two mechanisms can be mounted at the end of bracings and the third one is installed at the... 

A two-dimensional, two-phase, nonisothermal model was developed in this work to investigate the water transport characteristic and water distribution in a direct methanol fuel cell (DMFC). Emphasis is placed on exploring the water distribution in different layers of DMF. The water and methanol crossover through the membrane were considered with the effect of diffusion, electro-osmotic drag, and convection. Governing equations including the prton and electron transport, continuity, momentum, species transport for methanol, water, and gases species, and the auxiliary equations are coupled to determine the output parameters. These parameters are the concentration distribution of the species,... 

SQL injection is one of the most important security threats in web applications with backend SQLbased database. An attacker can abuse an application’s vulnerability to change the queries sent from the application to the database. Many techniques and frameworks have been proposed for detecting and preventing SQL injection. But most of them cannot detect all types of SQL injection such as second-order attacks. In this thesis, we propose a new method to detect and prevent all types of this attack. The proposed method is a kind of anomaly-based intrusion detection methods and could be considered as a proxy between the application server and the database server. The proposed method, can detect... 

Expanded polystyrene (EPS) products are mostly manufactured as disposable products, designed for a single use after which are recycled or disposed as solid wastes. EPS products are increasingly used specially in form of food containers and packing blocks and most of the time are left in nature without any kind of processing, causing environmental pollution. This project intends to investigate physical characteristics of lighter cement concrete with acceptable compressive strength for non-structural elements, made with different percentages of recycled EPS beads. A group of concrete samples are made by replacing coarse aggregate with equivalent volume of recycled EPS beads. Properties like... 

The emergence of semantic technology and its usage in different computational environments (especially the distributive environments) has increased the machine intelligence for more interoperability.This has resulted an abstraction (conceptual) layer above existing information and resources in these environments. Based on the unique characteristics of the semantic-aware environments, most of the proposed models for other environments are not applicable to this area, as they do not meet the security requirements of these environments. MA(DL)2-AM and SBAC are among the models that have satisfied a large portion of these requirements. Although documents are important assets of organizations...