Sharif Digital Repository

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... 

Nowadays, climate change is one of most important environmental challenges in all over the world. In addition to climate change, population growth, increase in water demand, which surpasses available resources so that the water system cannot meet the demands, and the subsequent growth in the development of water resources plans make watershed management become a challenging issue . In the last decade, due to significant reduction of precipitation, continuous increase in water development plans and utilization of too much water for agricultural and other uses, water inflow to the lake Urmia has reduced. Furthermore, Urmia lake have a strategic location which flows in three provinces of East... 

Most of the recent hydro-system researches lent themselves to integrated modeling of interactions between agricultural water demand and hydro-system operation for better agricultural water demand management. Large share of water consumption by agriculture sector and general acceptance of integrated water supply and demand management by water sector decision makers highlighted this approach in hydro-systems analysis. This approach in modeling helps to achieve a better management strategy for agricultural water demand and supply with the least reduction in agri-sector economic indices, while supplying industry, domestic and environmental target demands. However, agriculture, industry and... 

Two new dioxomolybdenum(VI) complexes have been synthesized by the reaction of N,N'-bis(5-chlorosalicylidene)-2,2'-dimethyl-1,3-propanediamine and N,N'-bis(5-bromosalicylidene)-2,2'-dimethyl-1,3-propanediamine as Schiff base ligands with [Mo(O)2(acac)2] in methanolic solution.and their electronic structures have been investigaged theoretically. The Schiff base ligands H2L1 and H2L2 were prepared by reaction of 5-Chlorosalicylaldehyde and 5-Bromosalicylaldehyde with 2,2'-dimethyl-1,3-propanediamine, respectively. The result of these reactions, was two complexes of Mo(O)2L1 and Mo(O)2L2 .The compounds were characterized by elemental analyses (CHN), and 1HNMR and IR spectroscopic techniques.... 

3D reconstruction of digital images is one of the sub- branches of computer vision which is used in various fields such as computer graphics, compute animation, etc. in general, two approaches exist for solving 3D structure problem. In the first approach to obtain the model, we need a certain distance of the whole object level at a certain point and to do so, a sensor is used which is directly interacting with the object. For instance, we use lasers and estimate the depth using that depth to make 3 D model. In the second approach we use the images we have at different instaces of an object (sensor is the camera that is sensitive to light). Using these data and the machine learning... 

Dislocations are one of the most important classes of defects in crystals. They have significant effects on the physical properties of crystals. They could be primarily created during the formation of a crystal or during the loading on specimen. Dislocation’s movement due to stress is the main cause of crystal plasticity. Since dislocation is a change in perfect crystal structure it is possible to identify it in the molecular level. However, the high computational cost of the MD level, has led researchers to using the multi-scale methods. Researchers have used many various multi-scale methods to study dislocations. The method used in this paper is based on energy. Total energy of system for... 

Scattering theory on locally symmetric space first was studied by Peter Lax and Ralph Phillips. They studied the and develop scattering theory on it. Without the Fourier analysis tools this theory was completed with a lot of computations. In this thesis first we try to construct Fourier analysis by definition Fourier transform then by means of new tools we prove very short version of scattering theory on locally symmetric space . In general case for studying scattering theory we need firs spectral decomposition of Hilbert space of square integrable functions locally symmetric spaces of rational rank one is achieved by quotient of symmetric space where G is Lie group and K is maximal... 

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... 

Reviewing trends of energy consumption in the world reveals that sooner or later energy resources will be depleted. This concerning rate of consumption has brought about more greenhouse gases (GHG) emission influencing deleteriously on environment and climate. Human has continued energy consumption to maintain and improve the quality of his life through industrial production. Industry as a significant energy user owns considerable contribution to this consumption. Several attempts have been carried out to develop energy management systems in order to improve the energy efficiency of industrial sectors. Whilst they are comprehensive and could be applied to any sector, there is lack of... 

The Tilor welded blank (TWB) two or more sheets with different thickness or strength which are welded together. The automobile designer are searching for new methods to reduce the cars’ weight and producing cost in order to diminish fuel consumption so they can survive in the competitive market. One way to achieve to this seemingly Contradictory demands, is using TWB in cars’ body. One of the most applicable methods to investigate the formability of metals sheets, is Forming Limit Diagrams (FLD). Three ways to determine the FLD are: Analytical Method, Experimental Methods, and Numerical Method. The experimental method to determine FLD, require metal sheets to undergo in different strain... 

Lipases (Triacyl Glycerol Acyl Hydrolase, EC.3.1.1.3) are multidimensional biocatalysts which have many applications in food industrials, dairy, fats and oils processing, detergents, synthesis of pure chemical and pharmaceutical materials, paper industrial and cosmetics. Generally, industrial enzymes are produced extracellularly, so their separation from a low-cost complex medium (usually used for production) is one of the cost stages in their production process. Filtration is the most economical method of separation in the production of enzymes, but due to the small size of colloidal particles and cell masses present in the fermentation environment, its use is subject to limitations. In... 

On account of the exhausting nature and increasing daily cost of the fossil fuels, it seems that replacing the fossil fuels by an alternative source of energy is inevitable. Moreover, in the remote areas that the electricity network is not accessible, the use of distributed sources (DSs) such as solar energy and wind energy is advantageous. Continuity of the supply and voltage control of the load in spite of the stochastic nature of the generated power of the renewable energy resources are the main concerns in the distributed generation (DG) systems. In this thesis, stand-alone operation of a DG unit comprising a solar unit and wind turbine as primary sources of energy is considered. A... 

Many improvements in the Inertance Pulse Tube Refrigerators (IPTR) have brought them to a place in which other Cryocoolers are gradually replaced. The Inertance Pulse Tube Refrigerators have high reliability, low operating and maintenance cost, low vibration and high efficiency due to lack of mobile components. These Cryocoolers are used in the cooling of infrared sensors, Cryosurgery applications, transportation, liquefaction of gases, and so on. The IPTR based on Stirling cycle and it uses helium gas as working fluid. Typically, a variety of compressors can be used as a driver, resulting in reduction in the lifetime of the IPTR. Thermoacoustic engines can be used to remove these... 

One of the significant as well as fascinating utilization of thermoacoustic is combining heat pump and thermoacoustic refrigerator. By means of supplied heat from hear source, the heat pump generates acoustic power which will be absorbed by refrigerator and forwarded to the heat source afterwards. In other words, thermoacoustic systems, from the side of which heat is absorbed, produces chill in the opposite side. Due to the novelty as well as heavy and precise research requirements, these systems has been neither designed nor manufactured in our country yet. In this research a laboratory prototype from aforementioned systems has been constructed, thereby paving the way for enjoying and... 

Scientists want to know how they can control fluids motion. They use electric fields for controlling the fluids in different dimensions. In small size, application of electric fields is very important because of biological applications. We use electric current and field for rotating freely suspended films. Here, we study soap, polar and non-polar liquids, MBBA liquid crystal and ferrofluids films. We show that the surface charge plays the crucial role in rotating the films.We study the correlation between rotation of a film and different physical quantities.Our experiments confirm that dipole moments of fluid molecules do not show a clear effect on the rotation. Increasing the dipole moment... 

Recently, quasi 1D (Q1D) structures of materials such as nanowires, nanorods and nanobelts with high surface to volume ratio (A/V) and small grain size devoted an extensive part of researches. This is due to their unique properties and thus various applications in manufacturing of nanometric devices. Niobium pentoxide (Nb2O5) as semiconductor with wide bandgap has been applied in various fields including: electrochromic devices, gas sensors, anti-reflective coatings, capacitors, photocatalysts , field emission and recently; antibacterial systems. In this project , initially niobium thin films was deposited on Si(100) substrate using RF magnetron sputtering method and then niobium oxide... 

Fluid-structure interaction plays an important role in the performance of various Microsystems. In many micro-devices such as micropumps, microvalves and micromixers, the fluid flow is driven by a vibrating solid membrane. Since the fluid also plays a role in resistance to the solid vibration and deformation, the solid vibration and the fluid flow are always coupled and a full fluid-structure interaction (FSI) analysis is required in order to investigate the performance characteristics of these devices. Since the frequency of the solid vibration is normally high in micro-devices, the time step size required for the finite element analysis of the fluid-structure interaction in these devices... 

The main objective of this research is to provide a framework by which decision-makers can evaluate and compare alternatives for sustainable development planning under uncertain dynamic future considering the risk and uncertainty associated with human judgment as well as the uncertain future. This approach combines the Delphi method, fuzzy set theory, and a discrete multi-criteria method based on prospect theory (TODIM). TODIM (an acronym in Portuguese for iterative MCDM) method is a particular multi-criteria approach based on the prospect theory. A qualitative Delphi technique is used to identify a set of qualitative sustainability criteria and to rate the alternatives accordingly. 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... 

In this work, hypereutectic Al-20Si-5Fe-2Ni powder was prepared by gas atomizing method. The alloy was fabricated by melting of commercially pure metals and re-melting at approximately 200 K above the liquidus temperature. The molten alloy was then atomized by nitrogen at a gas pressure of 0.8 MPa. The nozzle diameter was 3 mm. The aluminum alloy powders were milled under pure Argon atmosphere with a ball to powder ratio of 10:1 in a planetary ball for 12, 24, 36 and 48 hours. The gas-atomized and milled powders were then consolidated by cold sintering method. Microstructure and phase analysis were performed by SEM and XRD technique. Mechanical properties were evaluated by microhardness and...