Sharif Digital Repository

Nowadays, video on demand causes a drastic increase in network traffic that it is expected that network traffic surpasses 45 exabytes per month until 2022; consequently, utilizing distributed memories known as caches across the network to alleviate the communication load during peak hours is inevitable. Coded caching is a promising approach to mitigate and smooth traffic during peak hours in the communication network in a way that it creates coded multicasting opportunities in addition to delivering content to users locally. However, it suffers from imposed delay resulting from coding that makes this approach infeasible for delay-sensitive contents, namely video streaming applications. So... 

Surface Jet Pump (ejector) is one of the most widely used equipment in the industry, which can be used in the oil and gas industry, propulsion and refrigeration systems. One of the uses of surface jet pumps in the oil and gas industry is the use of high-pressure wells to transfar low-pressure wells. The purpose of this research is to measure the transmission feasibility of low-pressure wells using surface jet pumps and optimize surface jet pump geometry. The purpose of optimizing the geometry of the surface jet pump is to maximize the ratio of the discharge rate from the low-pressure well to the high-pressure flow (entranment ratio). One of the most common methods for optimizing the... 

Medical engineering advances in total joint replacements and society’s rising demand for long lasting materials, have proven it essential to manufacture materials that are more similar to the original tissue in the fields of mechanical, tribological and biological properties. Ultra High Molecular Weight Polyethylene(UHMWPE), is a polymer widely used in arthroplasty applications due to its biocompatibility, chemical stability and proper mechanical properties. In this study, UHMWPE-HAp nanocomposites reinforced with Zirconia and Graphene were manufactured aiming to reach a structure that is more compatible with bone tissue and also to improve overall properties. First, using ultrasonication... 

Transcranial direct current stimulation (tDCS) over the different brain regions has been documented in clinical and laboratory experiments. Anodal tDCS on the dorsolateral prefrontal cortex (DLPFC) has shown promising effects in enhancing cognition. Furthermore, such stimulations have been proposed in treatment of several neurological and psychological disorders. Investigations have verified the positive effect of such stimulations on drug addicts by diminishing their drug craving after stimulation. In spite of the extended research in this field, the effect of tDCS on different brain region and brain networks has yet not been studied through computational models. In this study, we evaluated... 

One of issues of human in this time is questions about epistemology. Human sometimes faced with this qustion that "Is it any knowledge for human being". Sometime he or she answers this question: yes and search for any knowledge around him or her. In the context of philosophy of science these question are very imortant. In philosophy of science one of major question is how many of factors in science is subjective and how many is objective? It is obvious that one of solution to answer this question is investigation of factors that construct the knowledege. Furthermore in this thesis I try to answer that question in context of Hikmat' Motealieh. In this context all of factors that involved in... 

Many simulation optimization problems are defined in random settings and their inputs have uncertainty. Therefore, in defining an optimal solution for these problems, uncertainties should be taken into account. The primary way of dealing with this , is Robust Optimization which finds solution immune to these changing settings. Aiming at finding a new approach for simulation optimization problems, this study investigates these uncertainties and robust methods. In the optimization problem, the goal and constraints are considered with separate risk measures and a related problem is defined as follows: Minimizing the weighted sum of all risks subject to the problem constraints. To solve the... 

Phenolic compounds are hazardous pollutants that are released into environment through wastewater discharges from variety of industries. Although good biodegradability has been reported at low concentrations, but at higher concentrations phenols are known to be antibacterial. In this study the Membrane Biological Reactor (MBR) with submerged hallow fiber membrane was operated at 25±2 ºC and pH=7.5±0.5 to treat a synthetic wastewater containing high phenol concentration (up to 5.9 g/l). Removal efficiency of phenol and COD were evaluated at four various “Hydraulic Retention Times” (HRT) of 24, 12, 8 and 4 hours. To test the tolerance of the bioreactor to phenol concentration various loading... 

Wireless Sensor Networks (WSNs) consist of sensor nodes that are connected to each other and are widely used in many applications to acquire and process information. WSN nodes are battery powered, therefore energy management is a key factor for long live network. Node radio transceiver unit uses the most part of energy resource of the node and as a result limits the network lifetime. One way to prolong lifetime of network is to utilize routing protocols to manage energy consumption. To have an energy efficient protocol, we can apply cluster organization on the network, where sensor nodes are partitioned into groups called cluster. Then, the whole cluster data is sent through Cluster Head... 

During years, supersymmetry has been a candidate for resolution of Higgs mass fine-tuning problem that is quadratic dependence of scalar mass radiative correction to UV-physics. So, supersymmetry phenomenology is of great importance. As accelerators have reached energy of 13 TeV in recent years and sparticles have not yet been observed, it is important to have a theory in hand, describing SUSY breaking dynamics with scale of SUSY breaking above the energies currently accessible to accelerators. As a result of mass-sum-rule constraint which holds in theories with spontaneous SUSY breaking at tree level and leads to light sparticles and even tachyonic directions, there are currently no... 

Biomechanical models require body posture to evaluate the risk of musculoskeletal injuries during daily/occupational activities like manual material handling (MMH). The procedure to measure body posture via motion-analysis techniques is complex, time-consuming, and limited to equipped laboratories. This study aims to develop an easy-to-use yet accurate model that predict human whole-body static posture (3D body coordinates and anatomical joint angles) during different MMH activities. Twenty healthy male right-handed individuals with body mass index between 18 and 26 performed 204 symmetric and asymmetric MMH activities. Each person reached (i.e., without any load in hands) the destinations... 

In recent years, Additive Manufacturing has been extensively used by various industries. These manufacturing processes produce components in a layer-by-layer manner; therefore, they do not impose any geometric constrains to engineers and provide designers with the freedom to design components. Nowadays, one of the primary goals of all industries is to utilize as few raw materials as possible; this way they can deal with the shortage of raw materials and improve their efficiency. Consequently, they implement topology optimization algorithms to design and produce their components. However, topology optimization algorithms result in complicated geometries that can only be fabricated by AM.... 

Effective theories compatible with quantum gravity have their specific features. These features are formulated within the framework of the Swampland program, in the form of Swampland conjectures. In this dissertation, we first briefly review some of the Swampland conjectures, their motivations, and implications. We then elaborate on our research aimed at better understanding these conjectures, and using them to gain a deeper insight into the properties of the universe. We proposed a bottom-up supergravity framework with string-inspired elements where the Higgs expectation value and the cosmological constant are correlated. In this paper, we studied the Higgs dynamics in nilpotent... 

Environmental pollution caused by human activities and advanced industrialization is an important problem in the modern era due to its toxic and adverse effects on the ecosystem and human health. Municipal solid waste, including food waste, is expected to increase due to increased urbanization, economic development, and population growth, while their bioconversion into value-added products can address this problem by reducing waste as well as minimizing dependence on fossil fuels and turn it into an opportunity. In this thesis, an integrated system is designed in which the organic fraction of municipal solid waste is converted into biogas through anaerobic digestion process, and after... 

Oil sludge is the most important waste of the oil industry, which, due to its production, needs to be treated and managed properly. In this research, an integrated process of its gasification in supercritical water environment and Allam cycle is proposed. Then, the necessary investigations are done to purify the syngas to produce clean syngas with hydrogen of more than 40%. This plant is compared with an integrated gasification system and gas turbine in the second scenario. The life cycle analysis of these processes is examined from both environmental and economic aspects. The results show that by using the integrated process of synthesis gas and electricity production, from 841.875 kg/h of...