Sharif Digital Repository

In this research Copper Nanoparticles have been synthesized by electromagnetic levitation gas condensation method which is a novel method for producing fine and pure metallic powders. Copper samples with 2 gr weight were levitated and then melted.the supersaturated vapor above the melted droplet have been cooled exerting pure argon and helium as cooling and carrier medias. To investigate the morphology and particle size of the produced nanoparticles, SEM and DLS analysis have been used and for characterizing the elements exist in the powder ,XRD analysis have been carried out.SEM images and DLS analysis of produced powder showed spherical cooper nanoparticles with narrow size distribution... 

Immobilization of β-D-galactosidase represents an important approach for development of lactose hydrolysis technology.Chitosan proved to be an excellent carrier for β-Dgalactosidase immobilization, by both covalent binding and sol-gel entrapment combined with adsorption. Among different preparation methods of chitosan support particles for covalent binding, emulsion cross-linking was the most efficient, producing narrow-sized microspheres, without aggregation.The best process parameters of β-D-galactosidase immobilization by covalent coupling on chitosan microspheres were found as 3% glutaraldehyde cross-linker concentration, enzyme loading of 27 mg protein/g dry support, 6 h reaction time,... 

Opinions and experiences of others give us valuable information in making decisions. Recently, with the expansion of using social networks and websites, people can easily share their opinions about miscellaneous things. This huge amount of information cannot be analyzed by individuals, so a system that automatically analyzes opinions is needed. This need invokes new field of research that is called opinion mining. User’s viewpoints could change during the time, and this is an important issue for companies. One of the most challenging sub-problems of opinion mining is model-based opinion mining, which aims to model the generation of words by modeling their probabilities. In this thesis, we... 

In this paper, an approach is proposed to estimate the location of the leaks in oil pipelines. The pipeline possesses a system of Partial Differential Equations (PDE). First, a closed-form solution is applied to the pipeline equations and the leakage location is found solving the steady-state equations. To tackle the case where the pressure and flowrate do not reach constant values, the initial estimations are provided by the closed-form solution. Then, the pressures, flow rates, and leakage coefficient are estimated by solving the system of differential equations. This system is then discretized with respect to the location variable to yield the system state equations which, in turn, are... 

Buried pipelines as vital arteries,which will play a major role in human life should be designed and implemented in such a way that withstand the least possible harm with regard economic issues.In this study we tried to use a physical model, the impact of pipeline buried in soil slope under dynamic load are examined.To achive this goal we use a rigid metal bax with dimensions of 301.5*101.5*155 cubic meters for modeling. Pipes used in these experiments has a diameter of 1.6 cm which are connected by a fulcrum to the wall box. In order to measure strain generated in the pipe we use a series of strain gauges that were installed using the pipe at some points. Physical models made on Sharif... 

This thesis proposes an energy management model for a residential prosumer building which is a multi-carrier energy hub in a grid-connected mode. Power may be bought and sold between the building energy system and the power grid. Solar panels and solar water heaters are integrated into the building's energy system to create electricity and heat, which may be used in a variety of ways: used immediately to meet the home's demands, stored in batteries and heat banks for later use, or sold back to the power grid to earn income. The energy dispatch is managed such that the overall energy consumption cost is minimized, considering the variation in electricity price (grid tariff), renewable energy... 

Since nanocatalysts have gained particular importance in various fields of chemistry, in this research, nanocatalysts based on metal-organic frameworks were initially made and used for multicomponent reactions, and C-C cross-coupling has been used. ZIF-8@SiO2@Pd, ZIF-67@MPDA, ZIF-8@MPDA, BMZIF@ MPDA catalysts are porous and stable cubic carbon-based catalysts based on nanoparticles. In addition, the product yields were good to excellent for all reactions under mild conditions, resulting from the superior activity of the synthesized heterogeneous catalyst containing cobalt and zinc. Also, these catalysts can be easily separated by a centrifuge and used in the next step without any noticeable... 

Diesel engines have widely used in past hundred years. During this time costly and extensive researches have been done to improve engine performance, which is going on. Important issues of these engines are higher specific power and efficiency and lower specific fuel consumption and pollutions formation. One of the best methods for engine performance improvement is matching a convenient turbocharger on engine. A turbocharger increases the engine air mass flow rate by increasing the inlet pressure and density. Due to increase of fresh air mass flow rate, fuel mass flow rate and power would increase. The aim of this research is to choose the convenient turbocharger for the OM355 naturally... 

A microbeam, actuated by electrostatic distributed force, is a flexible beam-shaped element attached to a fixed rigid substrate. Electrostatically actuated microbeams are extensively used in different applications such as signal filtering and mass sensing. When the input voltage exceeds a critical value, called pull-in voltage (V_pi), the flexible microbeam spontaneously deflects towards the rigid plate. Pull-in instability is a basic phenomenon considered in the design of the micro actuators. When the rate of voltage variation is low and consequently inertia has almost no influence on the microsystem behavior, the critical value of voltage is called static pull-in voltage (V_pi). However,... 

Antenna arrayss have long been utilized in many applications including communication, radar, and imaging. With the advancement of the telecommunication industry and the emergence of new requirements in the fifth generation of telecommunications, imaging and the Internet of Things, new antenna arrays are designed at higher operating frequencies and with particular specifications. One of the major challenges in using these types of antennas is unwanted mutual coupling in these systems. These couplings can occur between the antenna elements of the array itself, or between two or more arrays that are adjacent to each other. These couplings can seriously affect the performance of the system....