Sharif Digital Repository

Reverse osmosis membrane one of the common methods used for water desalination, today membrane, thin film composite(TFC) include three layers, top the these layers named selection layer, this poly amid layer contacted with feed water, sensitivity to chlorine in polyamide layer lead to high membrane chlorine sensitive. Difference methods used for enhance the chlorine resistance in polyamide membrane that categorized in three general categories, covering and protection of sensitive areas method has best results in comparison to other methods. In this research protection method choose and used, material that used, sanitized by result from surface analysis of commercial membrane manufactured in... 

Mathematical models are used for describing physical systems to make it possible to study and investigate the behavior of these systems and compare their performance and improve them. For this reason, a mathematical model for cardiovascular system and respiratory system is used to study how these two systems interact. The cardiovascular system model and the respiratory system model comprise four and two compartments, respectively. In fact, the combined model contains the left and right ventricles, body tissue, lung, systemic blood circulation, and pulmonary compartments. Heart rate and alveolar ventilation are assumed to be the quantities through them the central nervous system controls the... 

Metallic multilayer composites provide remarkable mechanical, electrical and magnetic properties. These kinds of composites have been recently processed by severe plastic deformation (SPD) methods. Accumulative roll bonding (ARB) is one of the SPD processes in which accumulation of strain by repeating cycles, leads to the ultra fine grained materials. The goal of this research is manufacturing of Al/Ni composite sheets by ARB process considering the effects of thickness and number of initial sheets on their mechanical properties and microstructures. The initial composites were produced by commercially pure Al and Ni as the matrix and the reinforcement, respectively. Thickness of the Al... 

Local scouring at the downstream of sluice gates in the erosive beds is one of the main concerns of hydraulic engineers because of the significant damage that it can cause to the hydraulic structures. It is important to control the local scour depth at downstream of hydraulic structures to ensure safety operation of these systems. Many researchers have conducted various studies to predict the maximum depth and diameter of scour hole and develop new methods in order to control this phenomenon. One way to overcome this problem is the use of apron, or non-erosive bed. In order to shorten the apron length or decrease the effect of the... 

Air enterance in to flowing water is something that is commonly seen in the water conveyance systems. The mixture of Air and water that flow together create a kind of flow that is called two phase flow. This kind of flow is often seen in culverts and water conveyance systems. There are different flow patterns in two phase flow. Considering pressure fluctuation, pressure drop and pressure recovery, slug flow pattern is the most complicated pattern among all.
Sometimes a singularity is used in a tunnel; one of the singularities that are frequently used in water conveyance system is expansion transition. In this study an experimental setup is used to model two phase slug flow, which passes... 

It is well known that arrays of antennas make it possible to steer the radiation pattern without steering a physical structure. For the past few decades this has been considered for many civil and military communication systems. Recently, ultra-short pulses are considered for high resolution radars and ultra-wideband communication systems. Systems with short pulses and large antenna arrays may benefit from high resolution in both temporal and spatial domains. But the implementation of the ultra-wideband feeding circuits for such antenna arrays is a hard job even with state of the art electronics. Optical technology has been applied, successfully, to a number of radio applications such as... 

Sharp crested weirs are one of the main and oldest means of measuring discharge in water conveyance systems. Many studies have been done on sharp rectangular weirs and have provided many relationships regarding the effect of geometric parameters and various factors on discharge coefficient of the weirs.In some places, due to existence of obstacles or barriers in the channel, it is impossible to create a symmetrical continuous weir some other cases,multiple or asymmetric weirs should be used, which is the main concept of this project.Since it seems unlikely that a purely mathematical model can review the impact of the multiplicity and asymmetry of these weirs without using empirical... 

High-power (108 – 109 W) RF pulses with a carrier frequency of C band and a duration of several oscillation periods can be produced through direct energy conversion of a travelling high-voltage pulse with the use of nonlinear elements.
Nonlinear transmission lines consist either of lumped nonlinear elements and provide spatial dispersion of excited oscillations or of elements uniformly distributed on a certain line segment. The first type of NLTL’s can be referred to NLTL’s with spatial dispersion. The second type of NLTL’s is ensemble of nonlinear oscillators with a characteristic natural frequency and temporal dispersion. In the first case, the duration of electromagnetic pulses is... 

During 1980s Additive Manufacturing technologies for the purpose of prototyping with fast and less expensive, under the name of Rapid Prototyping was invented. But nowadays under the vast progress made in this field, it possesses a notable place in different industries such as automobile manufacturing, aerospace, architecture, medicine and so on for part manufacturing. In all AM machines, the CAD model design part is manufactured by adding layered to each other. In this research, at first by explaining manufacturing process and current different technologies, the place of this manufacturing process in today and future industry, is analyzed. For discussing replacement of this method instead... 

One of the most important methods of controlling discharge in water industry which is widely used in irrigation, water distribution, waste-water engineering, drainage, flood control and other water related projects, is side weir. The hydraulic behavior of flow over side weir is spatially varied flow with decreasing discharge. Various investigators have related the weir discharge coefficient as a function of main channel upstream Froude number and the fraction of weir height to upstream depth . Performance of sharp crested side weirs with extended length (as labyrinth side weir with asymmetric geometry) has been studied in this thesis. The variables for this study are height of weir ,... 

If the size of the conventional telecommunication antennas -that are widely used in transmitting broadcasted radio and TV messages- is reduced by a nanometer size these antennas can be used at optical frequencies. Dimensions of these optical nanoantennas -that made of nanoparticles with highly permittivity- can be smaller than half of the wavelength. Based on this capability, optical nanoantennas have some important applications such as optical communication, photovoltaic devices, non-classical light, and optical sensing. After studying on optical nanoantennas and their features, in this project, we present distinctions between optical NAs and MW antennas and then investigate about different... 

The Deep Fading Effect is a destructive factor in communication systems, one of the solutions to eliminate it is the use of Diversity, and there are two types of indicators of Diversity, Spatial Diversity and Polarization Diversity. Spatial Diversity is a common method to reduce the Fading Effect while increasing the cost and increasing the volume of the communication station, which to optimize the cost and reduce the volume of the communication station, the Polarization Diversity Structure is added to the telecommunication system. To apply Spatial Diversity, several Antennas with different Polarizations are used, which The most common method in mobile telecommunication station systems is... 

Cloud computing has brought about many changes in the new business arena. These changes do not only include technological changes, but have penetrated the business models of many companies. For example, in recent years, many companies have migrated from their former systems to cloud computing for reasons such as easy and low-cost access to high-performance hardware and software systems, and to avoid maintenance and repair costs and security costs.Due to the economic conditions in recent years and the high cost of electronic items, the criterion of purchase price has become much more important than in the past among people when buying such goods. Now in the Iranian electronics market,... 

Wireless communication systems play a pivotal role in the daily lives of individuals. Given the escalating demand for higher data rates and enhanced reliability, there is an imperative need for cutting-edge communication technologies. Rigorous research is being conducted in these systems to refine and optimize antenna structures, aiming at augmenting performance, escalating data transmission rates, and mitigating interference. Microstrip antenna structures have garnered considerable attention due to their diminutive dimensions, adaptability to planar and non-planar surfaces, simplistic design, cost-effectiveness, and mechanical resilience. These antennas, featuring diverse patch shapes,... 

Emission of the greenhouse gases is a great concern and use of lightweight materials in transport vehicles has found a major importance in this respect. Metal/polymer laminated composites are of great interest due to their special mechanical properties and thoughness. Application of metal/polymer sheets is limited because of low bonding strength of metals and polymers in these sheets, which is not sufficient, to endure the stresses and strains during deformation processes such as deep drawing and bending. In this research, roll bonding of AA5052/Polypropylene sheets is investigated and the effects of bonding parameters on strength are evaluated and finally the bonding mechanisms during... 

The Southern Caspian Basin, which includes northern Iran, western Turkmenistan, and eastern Azerbaijan, is known as the Land of Fire due to its abundant gas springs. This region possesses unique geological features, including active mud volcanoes that are associated with the release of methane gas. These characteristics indicate a high potential for oil and gas exploration in the area. The Gorgan Plain, located in Golestan Province and bordered by the Alborz and Koupeh-Dagh mountain ranges and the southern Caspian Sea, witnesses several active and dormant mud volcanoes, which serve as indicators of energy resource presence in the region. The drilling problems faced in wells A and B in the...