Sharif Digital Repository

This reaserch is study on the performance of evaporation tubes used in mini jet engines which has been done experimentally using laboratory equipment. In this study, researchers have tried to simulate the laboratory conditions as much as possible to the real conditions inside the mini-jet engine, increase the accuracy of the results and increase the results and bring them closer to the results inside the mini-jet engine. The experiments are divided into two categories, cold and hot In cold tests, an attempt is made to study and investigate the types of two-phase flow regimes created by applying different fluid and air flow rates, and to select annular flow regimes from among them.... 

The main goal of this research is to investigate the effects of different types of heterogeneities on fluid flow and solute transport in saturated porous media. These heterogeneities are micro- and macro-fractures and cavities. For modeling micro- and macro-fractures we used an equivalent continuum model and extended finite element, respectively. Also, we modeled the problem by using mass conservation law for both components of the problem – fluid flow and the solute – and Darcy’s law. In modeling vuggy porous media, due to the high velocity of the fluid inside the free flow areas i.e. channels and cavities, we could not model the medium properly using Darcy’s law. Therefore, we had to use a... 

Over the past five decades, the proliferation of electronic devices and the advent of Internet of Things (IoT) technology have ushered in a profound revolution in integrated circuit technology. In contemporary electronics, digital integrated circuits rely predominantly on CMOS transistors. Among the notable limitations associated with CMOS transistors are their non-zero off-state current and limited sub-threshold slope. In response to these limitations, researchers have ventured into a burgeoning field known as "Beyond CMOS," exploring technologies like Tunnel Junctions, Carbon Nanotube FETs, and more. Additionally, alternative approaches that blend electronic and mechanical principles in... 

The numerical modeling of engineering contact problems is one of the most difficult and demanding tasks in computational mechanics. Frictional contact can be observed in many problems; such as: crack propagation, metal forming operation, drilling pile etc. In metal forming operations the required shape changes are obtained by either of forming process, such as pressing, hammering, rolling or extruding the material between the tools which are much stiffer than shaped material. Because of large difference between deformability of the tool and material, relative movements occur in contact area. These relative movements produce the normal and tangential stresses, which have important role on... 

Membrane bioreactors are increasingly being used for treatment of domestic and industrial effluents. A major operational drawback of this system is membrane fouling attributed to soluble microbial products (SMPs). In this study sampling were taken from microbial products on the surface and within the membrane pores and mixed liquir for mass characterization of protein content. Water-washing was used for surface and reversible portion of pore samples. Chemical wash with urea was used for further cleansing of SMPs within the pores. All samples were concentrate by precipitation with ammonium sulfate salt prior to analysis. Total protein content of samples was measured by lowry method. SDS-PAGE... 

Due to recent advances in laser technology and instruments, laser assisted machining processes has gained extra attention by scientists and industries. Naturally, effective modeling of the process is of great interest for researchers. Machining processes are generally modeled via FE tools and based on the requirements of model, it can be performed either mechanically or thermos-mechanically. About the LAM problems, it is basically meaningless to have a model without considering thermal effects. Hence, modeling is performed in two steps where through the first one, a thermal problem is solved to bring the temperature distribution of the work piece as the initial conditions of the next step.... 

Performance of reinforced concrete frames is highly dependent on detailing of the joint connections between its members, such as beams and columns. To have a good structural behavior, joints must show ductile behavior and designed based on the philosophy of strong column-weak beam. In the case of sever lacking ductility, strength or even rigidity of the connections, or having a weak column-strong beam, in the existing structures, there is a need for seismic upgrading of the connection. There are several ways for seismic upgrading of this type of connections.In this research, using steel plates for seismic upgrading of Concrete Beam-Column connections subjected to axial and cyclic loads has... 

The purpose of this study was evaluation of the performance of wastewater treatment system of Imam Cane plant for treatment of MDF factory wastewater. At first, It was required that microorganisms acclimation with presence of indigestion components in MDF factory wastewater, therefor the planned flow of wastewater was added to the lagoon after enhancing of system efficiency and concentration of UASB reactor sludge. The flow of MDF factory wastewater was mixed with canefactory wastewater stream and then mixed flow was introduced to UASB reactor. At first, 82 m3/day of wastewater was introduced to lagoon and after 28 day efficiency of treatment system reached to 68.9%... 

Many aroma compounds of fruit juice recovered by thermal processes like evaporation and distillation can lead to undesirable chemical changes and even their loss. Pervaporation is a promising process for the recovery of volatile organic compounds from their aqueous solutions. In the present work, pervaporation recovery of Butyl acetate as a model solution ofgrape juice aroma compoundwas evaluated with polyethersulfone (PES) and ethylvinylacetate (EVA) membranes. PES membrane generally showed better selectivity so that the separation factor at the concentration of 500 ppmand the temperature of 30°C for PES and EVA membranes, respectively, was 230.78 and 156.9. The effect of two operating... 

Membrane fouling is the main cause of permeate flux decline and loss of product quality in reverse osmosis (RO) systems, so good pretreatment of the feed solution was required to prevent membrane fouling. One of the most common applied pretreatment methods to prevent or control the scaling of different salts in feed water is to add scale inhibitors. Due to the great variety of commercial scale inhibitors RO plant operators must evaluate these chemicals before use in real plants. In this project three different types of antiscalants at concentrations of 10 ppm and one type of magnetic descaler on the RO pilot for the R.O plant feed water of agro-industrial Hakim Farabi evaluated and function... 

In this thesis, we study security features of the networks which use linear network coding to multicast information to some nodes of the network in presence of a wiretapper and also an active intruder. We consider information theoretic security in which we assume no computation limits for enemy. Thus, we take advantage of the essence of network coding instead of cryptographic tools to improve security features of the network. First, we show how providing shannon security for such networks in presence of wiretapper, leads to different cost in multicast rate, depending on initial network code designed. Based on this, we present a modified secure network code design which can provide perfect... 

Current research studies the effect of electromagnetic field on reducing precipitation on membrane surface in reverse osmosis. Reverse osmosis is one of the most widely applied methods for water desalinization. Despite its advantages over other desalinization techniques, suffers from shortcomings such as blockage of membrane surface. Use of magnetic fields for reducing precipitation in process equipment, the so-called magnetic treatment, has been studied and practiced for decades. This research intends to study the effect of electromagnetic field on water and its mineral content, and the possibility of its application as a method for reducing precipitation and blockage in reverse osmosis... 

In this study three type of nanofiltration membranes were prepared from PVC for water softening; (i) asymmetric PVC nanofiltration membrane, and two different thin film composite (TFC) membranes: (ii) polyamide (PA)/PVC composite membrane (iii) poly vinyl alcohol (PVA)/PVC composite membrane. Asymmetric nanofiltration membranes were prepared by phase inversion. The effect of PVC concentration, solvent (THF) and additive (PVP) on morphology and performance were studied by scanning electron microscopy (SEM) and measuring pure water flux and salt rejection. Increasing PVC concentration decreased pure water flux and increased salt rejection. Adding tetrahydrofuran(THF) decreased the pure water... 

Many aroma compounds of fruit juice recovered by thermal evaporation and distillation processes can lead to undesirable chemical changes and even their loss. Pervaporation is a promising process for the recovery of volatile organic compounds from their aqueous solutions. In the present work, pervaporation recovery of Ethyl acetate as a model solution of apple juice’s aroma compound was evaluated with polyvinylidene fluoride (PVDF) and ethylvinylacetate (EVA) membranes. For PVDF and PES membranes in the feed concentration of 250-1000 ppm and the operating temperature of 30 ºC, separating factor , respectively, was obtained in the range of 67-70 and 49-53, and also total permeation flux was... 

Two-phase fluid flow physics in porous media is applied in various fields. Studies have shown that wettability and surface tension, which represent fluid-rock and fluid-fluid interactions, have a significant effect on the dynamics of the immiscible displacement. Although the effects of wettability and surface tension on the macroscopic behavior of fluid flow are known, there is less understanding of it at the micro scale. Considering the essential role of wettability and surface tension in various fields, this project seeks to investigate the effects of wettability and surface tension on the movement and distribution of fluids and the dominant displacement mechanisms within the porous media... 

Optical tweezers consist of a tightly focused laser beam. A particle with refractive index greater than that of the surrounding medium can be trapped at the focus of the laser. The trapped object experiences a three-dimensional Hookean restoring force towards the focus. Nano (micron)-sized spheres can produce forces in the range of few pico-newton to few nano-newton. This range covers a large number of the forces, which contribute in biological processes; therefore, optical tweezers are very often used for micromanipulation of biological tissues. In a typical micromanipulation experiment it is crucial to perform proper positional calibration prior to use. There are several calibrate methods... 

Magnetic shape memory alloys (MSMAs) are a new class of smart materials that exhibit characteristics of large recoverable strains and high frequency. These unique characteristics, make MSMAs interesting materials for applications such as actuators, sensors, and energy harvesters. This thesis presents a three-dimensional phenomenological constitutive model for MSMAs, developed within the framework of irreversible continuum thermodynamics. To this end, a proper set of internal variables is introduced to reflect the microstructural consequences on the material macroscopic behavior. Moreover, a stress-dependent thermodynamic force threshold needed for variant reorientation is introduced which... 

In this study, modification of Polyvinylidene fluoride membrane in order to reduce membrane fouling in membrane bioreactors is investiged. To achieve this goal, chemical modification and grafting methods were used. Initially, by chemical modification, the reaction was made to make hydroxyl groups on the membrane surface. The hydroxyl functional groups were used as a site for connecting of subsequent monomers. Finally, the lysozyme enzyme was used as the main modifier to improve the hydrophilicity and antibacterial properties of the membrane surface. To evaluate the performance of the modified membrane in comparison with the pristine membrane, different tests, such as water contact angle...