Sharif Digital Repository

Future of the Karkheh River Basin and its people’s livelihoods clearly depends on natural resources like water, soil, vegetation and livestock. As water is the most limiting natural resource in this basin, any increase in water productivity will almost certainly benefit rural livelihoods. To ensure the sustainability of the improvements in water productivity, assessment of the possible impacts of climate change on hydrology and water resources in the basin is necessary. In this study the potential impacts of climate change on hydrology in the Karkheh River Basin were assessed using a macroscale hydrology model driven by 21st century simulations of temperature and precipitation downscaled... 

In recent years, two-layer sheets have been used in various industries. In this research, the formability of a two-layer sheet which is made of 1.35 mm steel and 0.45 mm copper sheets has been studied. The two-layer sheet used in this study was made by explosive welding method. In order to investigate the formability of the sheet, forming limit diagram was determined. First, Marciniak-Kuczynski (M-K) model was used. In order to determine forming limit diagram using this method, the two-layer sheet was equated with a single-layer sheet and MATLAB software was used. The two-layer sheet was also modeled in finite element software ABAQUS. In order to determine the forming limit diagram, Nakazima... 

According to the rapid growing in communication devices, users need higher rates for their usages. Fiber optics is one the major choices to support such rates. One of the simplest and cheapest networks is Local Area Network (LAN) as a Passive Optical Network (PON). In these networks, some computers are locally connected to a passive optical device and communicate through it. Multiple access to a shared channel is an important task in such a network. In this thesis, Code Division Multiple Access (CDMA) is used and a new algorithm for Multiple Access Control Sublayer (MAC) based on scheduling will be developed to improve Quality of Service (QoS) and stabilize the network.
In the scheduling... 

Wireless sensor networks (WSNs) are composed of many independent spatially-distributed sensor nodes where communicate their information acquired from environment to shape a uniform view of their managed scope. Using WSNs in places which human can hardly attend uninterruptedly, as well as constraints such as low power consumption, low price, small size, and limited radio range, are the biggest challenges for researchers and WSN designers. Supplying security is yet another common challenge of using these networks. The beginning chapters of this dissertation introduce the most important security mechanisms in WSNs, that is, key management and cryptography. Since each application has its own... 

Smart heat-sensitive polymers play a unique role in drug delivery systems due to reversible behavior in response to environmental changes, especially temperature changes. Among the heat-sensitive polymers, UCST polymers due to their specific behavior and very little-known polymers with this feature are the subject of many new researches. In the present study, New designed temperature-sensitive polymers with UCST capability based on acrylamide and vinyl acetate were synthesized. These copolymers were synthesized in different percentages of acrylamide by free radical polymerization in solution conditions. All polymers compounds were characterized by H-NMR, FT-IR, DSC and GPC measurements. The... 

The amount of fresh water suitable for various uses is decreasing day by day. This may be due to evaporation or contamination of water or such. Heavy metal cations, dyes, oils and solvents are the most important substances that contaminate water. There are various ways to remove these contaminants, one of which is the absorption of these substances by suitable absorbents. Carbon compounds have attracted much attention among all the absorbents used so far. The aim of this study is to produce carbon aerogels from an economic and modify its structure and properties by adding graphene nanosheets. In this study, Novalak-graphene oxide (GO) gel was fabricated using solvent-saturated vapor... 

Nanocrystallization kinetics of amorphous Finemet-type alloys was studied using Isokinetic and Isoconversional methods (Kissinger model-fitting method, Vyazovkin advance method, Kissinger–Akahira–Sunose(KSA),Flynn–Wall–Ozawa(FWO),Tang and Starink) under isothermal and non-isothermal conditions. Effects of chemical composition on the nanocrystallization kinetics, microstructure and magnetic properties of Fe73.5Si13.5B9Nb3Cu1 and Fe77Si11B9Nb2.4Cu0.6 alloys were also investigated. Kinetic triplet (activation energy, frequency factor and reaction model) were determined by these methods and compared for the alloys. According to isoconversional methods, the activation energy is variable as a... 

AZ91 is the most applicable alloy of magnesium alloys.Semisolid stir welding of AZ91 magnesium alloy was investigated due to its welding problem such oxide formation, hot cracking in weld metal, and high residual stress through solidification with special focus on the effect of the welding temperatures, stirring rates, and tool shape. The interlayer with thickness of 2mm was located between two AZ91 pieces with 7.5mm thickness. Then, they were heated to the desired temperatures (515C, 530C and 540C), the semisolid temperature of both base metal and interlayer. A grooved stirrer with six rotational speeds from 0rpm to 2000rpm was introduced into the stir weld seam and the welded coupons... 

In this thesis, the value-ladenness or value-neutrality of technology, new social media and as a result Instagram is investigated. It is also discussed whether values can be taken into account during the design process of technical artefacts, including new social media and Instagram, and methods are developed for this purpose. Several methods have been developed for this purpose, some of them and their compatibility with modern social media are explained; including the Value-Sensitive-Design method and the disclosive computer ethics design method. The frameworks of ethical philosophy such as virtue ethics are reviewed and the appropriate ethical framework for the analysis of new social media...