Sharif Digital Repository

In the future mobile network 5G will offer high speed and low delay but millimeter wave link are poor at penetrating into solid objects. Thus future network will be a hybrid of traditional sub-6GHz macrocells and denser 5G small cells. We develop a general analytical model to derive delay and throughput in this network. First we analyse the initial access delay which is very important in Internet of things and machine to machine communication. Then we go into data delay of network. With the foreseeable explosive growth of small cell deployment, backhaul has become the next big challenge in the next generation network. We analyse two option of fiber and millimeter wave. At the end we have end... 

Finding a path between two specified points is one of the most common problem in computational geometry. The minimum-link path problem is in this category. The minimum-link path between two points is the path between these points with the minimum number of segments. Minimum-link paths have application in areas such as computer graphic, geographic information systems, robotics, image processing, cryptography and VLSI.In this thesis we study variations of the minimum link path problem. Specifically we consider the constrained minimum-link paths in which the path must passes through some given
regions. We detected a flaw in a previously presented algorithm and propose a method to fix this... 

As far as reliable supply and cost-effective methods of power delivery to end-users are concerned, new advancements in smart grids and, in particular, smart pricing are of high significance to grid operators. In the recent decade, there has been a considerable raise in penetration of renewable energy resources and also the number of hybrid electric vehicles which can act as a huge mobile storage in the network. Hence, finding a practical and cost-effective method of management of all these new resources and avoiding potential problems associated with them seems to be of high importance. In this study, first, the response of demand to pricing signals has been modeledAfterwards, the response... 

The behavior of boundary layer under the effect of the sweep angle is considered. The measurements were performed by a pitot tube rake. Three models with various sweep angels at angles of attack -2, 0 and 2 degree were tested. Both tip and root of all wings were closed by flat plates in order to prevent the flow to roll-up. However the flow field on the wing was still three-dimensional because of the sweep angle. The velocity on the wing has two components; longitudinal and lateral. The cross flow emerges due to the non-equilibrium of pressure and centrifugal forces. The velocity profiles showed that the magnitude of cross flow was stronger near the leading edge of the wing. The cross flow... 

In this piece of work, a gravity model is suggested as Iranian non-fuel export model to OIC countries. The most important results out of this model are the acquired coefficients of two variables, namely “ECO membership” and “Economic and Trade Freedom of Importer”. At first, we expected that for importer, being a member of ECO would increase the amount of trade with iran. Surprisingly, this is not what we see in a model. In fact, as ECO has not achieved any tangible success in increasing trade between its members, eastern Asian Muslim countries has become an important trade partner for iranians. This result is compatible with other pieces of researches about ECO. “Economic and Trade Freedom... 

Today’s growing interest to the underwater explorations and navigations demands to design appropriate underwater communication methods and systems. However, radio frequencies which are widely being used in free space communications, can’t be a good candidate for underwater wireless communications, due to their sever attenuation in water. On the other hand, underwater acoustic communication has been widely studied and implemented in the past decades, inspired by suitable propagation of acoustic waves through the underwater medium. Nevertheless, acoustic communication systems have limited bandwidth, lower propagation speed and lower security than optical counterparts, which suggests underwater... 

In present research, a cohesive based finite element model has been introduced to estimate median crack depth during mechanical machining on optical glasses. Development of the machining numerical model has been initiated by investigating the indentation process. Experimental results of this step have been calibrated primary numerical model which has been used in the scratch process. Due to differences between the scratch mechanism and indentation one, mathematical bases fracture formulas and cohesive relations have been developed. After extracting primary result, using them in the scratch model and developing the primary model, ultimately numerical model has been evolved to an abstract... 

Visible light communication (VLC) uses huge license-free spectral bandwidth of visible light for high-speed wireless communication. Since each VLC access point covers a small area, handovers of mobile users are inevitable. In order to deal with these handovers, developing fast and effective resource allocation algorithms is a challenge. this paper introduces the problem of mobility-aware optimization of resources in hybrid VLC and 5G radio access technologies networks using the T-step look-ahead policy and employing the notion of handover efficiency. It is shown that the handover efficiency can correlate the overall performance of the network with future actions based on the mobility of... 

Hydrothermal supercritical method is one of the most suitable methods for metal oxide nano powder, ceramics and mineral catalyst synthesis. Metal oxides nanopowder in its pure or mixed form has wide potential application as chemical industrial catalyst, hot Superconductors, magnetic material, gas sensors and car catalyst convertors. One of the most important metal oxides aspects of application is uranium oxide as nuclear reactor fuel is used. In addition, UO2 is selective catalyst for converting methane to methanol process and Decomposition of organic Chlorine material. In Supercritical hydrothermal method done in high pressure reactor with critical to fluid, is new method for the... 

Lithium has 9 isotopes which two isotopes are stable and remaining isotopes are unstable and have half-life. Lithium stable isotopes include 6Li and 7Li that their abundance is 7.53% and 92.47% respectively. Importance of lighter lithium isotope appears for its small cross section against thermal neutron and producing fusion reactors fuel in nuclear industries. Thermal neutron absorption cross section for 6Li and 7Li are 950 barn and 37 mbarn respectively. Interesting of these isotopes in nuclear industry is due to the large difference in the absorption cross section.6Li compounds implied for tritium producing in coat of nuclear fusion reactor with DT fuel. Following tritium is used in... 

In this study some experiments were performed to investigate the effect of sweep angle on the transition location of laminar flow to turbulent flow. Three half wing models were used, each having a different sweep angle but with the same aspect ratio in various angles of attack. Two flat plates were used at the ends of the swept wing models to prevent the flow from rolling up over the wing. By simulating flow over infinity swept wing by eliminating tip vertices, the effect of sweep angle on flow transition phenomenon was investigated.
The experiments included the study of transition flow via hot-film sensors, which were glued on the wing surface. We found that the small leading-edge... 

Foil gas bearings are compliant surface, self-acting hydrodynamic bearings that use ambient gas as their working fluid. They do not require external pressurization and are typically constructed from several layers of sheet metal foils. In high-speed, high-temperature applications the GFB’s have the advantage of developing higher load capacities than with fixed geometry gas bearings. Since GFB’s have a complex structure consisting of a spring-like substructure with an overlying flexible surface, there exists a great variety of permutations on any given design. At current work presents a 1D model for GFB with couple solving Reynolds and Euler-Bernoulli beam equation. This mean top foil assume to... 

Natural boron consists of two stable isotopes, mass 10 (19.3%) and mass 11 (80.7%). 10B isotope has a large thermal neutron capture cross-section and it therefore, used widely in such aspects as modern industry, military equipment, medical science and so on. specially the demand of atomic energy industry for the boron isotope is increased severely. So the separation of 10B from natural boron has received very wide attention at present. There are many kinds of methods on the boron isotopes separation, such as chemical exchange reaction and distillation in boron trifluoride method, ion exchange in boric acid solution method, counter current recycle membrane cascades in boron trifluoride... 

Lameness in dairy cattle is a crucial welfare issue in dairy industry, and over the years scientists are attempting to present a detection method. In recent years it is attracting more attention to make the identification and discrimination of sounds and lames systematic and automatic. Right now, the most hopeful results have been obtained through the measurement of Ground Reaction Forces (GRF) of hooves, and analysis of load distribution between four legs, which seems applicable for wide use in dairy industry. However, the accuracy, validity, and reliability of discrimination is still far from an acceptable point, that is because of a great lack in understanding quantitative effects of the... 

In this study the feasibility of xenon separation from xenon-krypton mixture was investigated by utilizing of the chromatographic column filled with nano and micron sized NaY zeolite. For this purpose the nano NaY with the yield of 100% related to Al2O3 and the average size of 98.6 nm was synthesized through the clear solution method with the mid-adding of NaOH. Furthermore, a novel method for granulation of nano zeolite was developed by utilizing sodium alginate as an external template. In this method the production of uniform spherical granules with the different sizes in the range of several milimiteres to 100 µm was easily performed. Moreover, the results showed that the adding of... 

Natural boron includes two stable isotopes 10B and 11B with 19.3 and 80.7 weight percent respectivley.10B isotope has a high thermal neutron absorption cross section. So isotope 10B material is suitable for making atomic reactor control rods. Other and even more important applications of 10B are in disclosing neutrons in order to measure neutron reactors fluxes and also are in nuclear physics laboratories and medical radiation. This isotope also is used in the pharmaceutical and the military industries. There are several methods for separating boron isotopes. Among the distillation methods, thermal diffusion of BF3, distillation of BF3, distillation of methyl borate, boric acid distillation... 

Technology, especially in recent centuries, has changed human form of life. Case studies show that there is a mutual relationship between human being and technology; Human is a technological being and technology is also a social entity. Therefore, trying to develop a conceptual framework to describe the important role of technical artifacts in our life can be regarded as a legitimate philosophical concern. Peter Paul Verbeek is one of the contemporary philosophers who take this concern seriously. He, by using the doctrines of The Empirical Turn in the philosophy of technology, has developed a lexical system, called post-phenomenology, to describe the role of Technology in human’s perception... 

In this work, graphene oxide (GO) and Amino ethyl phosphonic acid (AEPA) functionalized graphene were synthesized using chemical method. In addition, reduced graphene was prepared by chemical and supercritical methods. Physical, chemical, morphological properties of as-synthesized materials were investigate using XRD, FTIR, RAMAN, UV, TEM, TGA, and BET. Thickness of monolayer GO which synthesized using Hummer’s method was evaluated 1 nm using AFM. FTIR and CHN results were affirmed the presence of AMPA onto graphene nanosheets. Adsorption properties of functionalized graphene for Th ions from aqueous solution was examined. Isotherm adsorption results demonstrated that maximum adsorption... 

Due to both dynamic and opportunistic spectrum access, Cognitive radio networks is a promising solution for spectrum scarcity problem. In cognitive radio networks, users need to have a control channels in order to cooperate for sharing the sensing information, channel sharing and etc. In Ad-hoc cognitive radio networks because of the absence of infrastructure and central nodes, every user runs a distributed algorithm to create a common control channel. If the control channel gets jammed, network’s performance degrades dramatically, therefore the jammer’s target in cognitive radio networks is the control channels to disturb the networks’ performance. The traditional solution to confront... 

A number of players are positioned on the vertices of a finite graph, and each is wearing a hat whose color has been randomly and equally likely selected from a finite set of colors. Player A sees Player B if and only if there is a directed edge from the vertex corresponding to A to the vertex corresponding to B. The players must agree on a specific strategy before the game begins and carry it out. Once the game begins, no communication is allowed between the players, and each player must simultaneously guess the color of their own hat. The team wins if at least one guess is correct. For a given directed graph, we define the 'guessing number' of the graph as the maximum number of colors for...