Sharif Digital Repository

In the framework of the Standard Model of Particle Physics, Quantum Chromodynamics (QCD) is known to be the only theory which describes the strong nuclear force. Because of the property of asymptotic freedom, perturbative methods fail to describe QCD at low energies. Here, mesons and baryons build the main degrees of freedom of QCD. To describe the dynamics of mesons at low energies, nonperturbative methods are used. The Nambu–Jona-Lasinio (NJL) model is one of the most important effective models, which is used to study the nonperturbative phenomena of QCD at low energies. The Lagrangian density of this model includes a local four-fermion term,which descibes the interaction between the... 

Quantum Chromodynamics (QCD) is the theory of strong interaction. Two main properties of QCD in low energies are chiral symmetry breaking and confinement. At finite temperature, QCD exhibits a certain transition from a chirally broken phase to a chirally restored phase and liberation of color charge. Lattice QCD at finite temperature shows a crossover transition at vanishing or small chemical potential while the model-dependent studies, e.g. the Nambu-Jona--Lasinio model predicts a first-order phase transition at large chemical potentials. The first order and crossover transition lead to the existence of a critical point in the phase diagram of QCD. Determining the nature of the phase... 

Polyampholyte hydrogels are hydrophilic networks that contain both positively- and negatively-charged functional groups on their structure. Polysulfobetaines are the most important type of polyampholytes, which have been extensively studied. However, these hydrogels exhibited poor gel strength causing limitation of their applications. Consequently, much attention has been focused on the preparation of nanocomposite hydrogels with high gel strength and lower cost using organomodified clays. In this project, Novel polyampholytic superabsorbing nanocomposites based on the zwitterionic sulfobetaine monomer [3-(methacrylamido)propyl)]dimethyl(3-sulfopropyl) ammonium hydroxide (MPDSAH) were... 

We consider a special class of Congestion Games enhanced with a notion of time.Network Routing problems, such as road traffic networks, computer neworks, and evacuation problems are some applications of this class of games. Two subclasses of these games, namely atomic and non-atomic is considered in this article, both of them introduced in 2009. Some of the existing results are Nash equilibria existence proof for “single-source single-sink” case, and a mechanism for improving price of anarchy in the non-atomic subclass. There are also some results in the atomic subclass of this game.We extend both models of atomic and non-atomic subclasses to “multi-source,multi-sink” configurations. We call... 

As nuclear energy continues to be used as a useful energy resource, waste management, especially management of high-level nuclear waste (HLW), will always be a major concern, as the future generations should not be deprived of the valuable benefits of this energy. Vitrification of liquid high-level radioactive waste (HLW) has received greater attention, worldwide, than any other high-level waste solidification process. The high solubility of HLW in borosilicate glass, the controllable temperature of this type of glass and its low leaching rate in repository environment, have introduced borosilicate glass as a suitable host for HLW immobilization. In this project, the immobilization of the... 

Acidizing is one of the widely used practices of formation damage remediation. The success of this rather expensive job depends on the precise design and operation. Though, improper execution of an acid job, not only does not improve the formation damage but also can contribute to even more damage itself. For this purpose, it is critically important to thoroughly design an acidizing job conducting extensive lab experiments and utilizing numerical tools before operation in order for a successful acidizing. Unlike, carbonate acidizing, the chemistry of sandstone acidizing is very complex and challenging because of the wide variety of minerals and aqueous species present in the system. Hence, a... 

In this project, in general, we have studied the particle production during and after the Inflation.Today, the Inflation is considered as a part of the standard model of cosmology and it solves so-called two cosmological problems: flatness and horizon problem. According to it,the universe after the inflation becomes supercool; however, the thing we observe today is in contradiction with this theory. The Reheating era is a time period in which the inflationary field gets to its minimum of potential and starts to socialite. Actually, here is the place in which the phenomenon of the particle production occurs. This period is called the Reheating era. therefore, it seems all particles which we... 

The ever increasing usage of modified binders in road construction requires that the effect of different modifiers on the performance characteristics of the asphalt binder be determined through laboratory testing. The current Superpave protocol for performance grading asphalt binders has proven to be insufficient to properly characterize modified binders, thus researchers have searched for other testing methods to complement or possibly replace some of the Superpave tests. Most notable are the time sweep test for fatigue resistance, the multiple stress creep and recovery test (MSCR) for rutting resistance and the direct tension test (DTT) for low temperature cracking characteristics. In the... 

Binder modification, to improve the rheological properties and meet the standard requirements, is a common practice. The modification is usually done by adding polymers like Ethylene Vinyl Acetate (EVA) and Styrene Butadiene Styrene (SBS), waste materials like crumb rubber, or acids like Poly phosphoric acid (PPA) or by air blowing techniques. High temperature rheological properties of modified binders are usually improved by using polymers while the low temperature rheological properties mostly depend on the original binder. Therefore, the rheological properties at low temperatures do not show clear improvements in the modified binder compared to the original binder. This indicates that a... 

Asphalt concrete is a composite mixture of three phases; aggregate, bitumen and air void. Stress and strain distributions obtained from macroscopic modeling yield different results due to distinctly different mechanical properties of the above-mentioned phases. In this study a more exact analysis of the stress and strain, were carried out by considering the mixture as a two-phase composite; aggregate and mastic phases. Asphalt concrete was considered a composite material consisted of sand mastic and aggregate. Aggregate and mastic phases were separated and response of the loaded asphalt mixture was investigated. Aggregates finer than 2.36 mm in diameter, filler and bitumen consist the... 

The numerical simulation of asphalt concrete and pavement has gained considerable attention in recent decades. Information about the response of asphalt pavements during construction and in-service traffic loading is required by pavement specialists for improvement of pavement analysis and design methods. The goal of this study was to propose a constitutive relationship and a numerical modeling method for asphalt concrete compaction in the laboratory and in situ. Asphalt binders exhibit rate-dependent viscoelastic and viscoplastic mechanical behavior in asphalt concrete. The current study examined the viscoelastic and viscoplastic mechanical behavior of asphalt concrete under various loading... 

Underwater robots are capable of performing a wide range of underwater operations such as research, sampling, hydrography, rescue, and more. These robots are generally categorized into two main types: remotely operated vehicles (ROVs) and autonomous underwater vehicles (AUVs). AUVs offer significant advantages due to their lack of reliance on human operators, including extended operational range, longer operational duration, and reduced human risk. In the design process of any underwater robot, a specific dynamic model is developed based on the robot’s geometric features and the specifications of its appendages, including control surfaces, thrusters, and buoyancy tanks. This involves... 

With the increasing importance of the sustainable development perspective, coupled evaluation of the environmental, economic, and functional performance of pavement maintenance programs needs to be considered. This task requires the use of data and models from different sources, which introduce uncertainty in the analysis. The use of probabilistic analysis may allow decision-makers to reach more realistic conclusions. To this end, all phases of the pavement life cycle, including material production, construction, use, and salvage at the end of life, should be considered. The effect of pavement-vehicle interaction (PVI) in the operation phase has received less attention from researchers. In...