Sharif Digital Repository

Knowledge of the properties of aerosols is of great importance in aerosol science. To gain a better understanding of particle properties, behaviors and dynamics, measurement capabilities are crucial and inevitable. The most critical steps in the aerosol size measurements based on electrical techniques are the processes of particle charging and neutralizing. Corona discharge is a paramount method among all aerosol charging methods because of highest concentration of produced ions, which is essential for the efficient particle charging, based on diffusion and field charging mechanisms. The only known method, which could be applied to provide required conditions for these two charging... 

A Lab-On-a-Chip (LOC) is a device which can integrate one or many laboratory functions on a small chip with millimeters to few square centimeters in size. LOC is a subset of MEMS devices and known as “Micro Total Analysis Systems” (µTAS) as well. LOC technology is closely related to microfluidics which primarily describes the physics, manipulation and study of minute amount of fluids.In this research we tried to simulate the performance of a microfluidic device for counting blood cells to find main factors of it for design and manufacturing. This research has two main sections, hydrodynamics of fluid inside the microchannels and finding electrical performance of designed Coulter counter for... 

Discovering new medicines and generally medical researches, are time consuming and expensive. But recent achievements in cell culturing methods and micro and nano-engineering techniques have enabled the researchers to investigate new medicines in a lesser time and price. Huh et al. successfully fabricated the lung on chip device. This device is consisted of three chambers. The middle chamber is separated in two equal parts and side chambers were considered in order to apply normal breathing. Periodic deformation was needed to apply the natural condition of cultured cells by expansion and contraction. Numerical simulation was needed to investigate the properties of flow in this kind of... 

Recent investigations on organs-on-chip devices have broadened our insight into the functions of the organs and their responses to pharmaceuticals. Studies on improving the efficiency of these chips are on going. The development of chips for growing various organs and possibly their possible interconnection are other hot topics in this field. This research is an attempt to simulate a Lung-on-a-Chip (LOC) device using Ansys Fluent software. Currently a new experimental technique for setting up a lung-on-a-chip device has been made public (Zamprogno et.al.ˏ̎ Second-generation lung-on-a-Chip with an array of stretchable alveoli made with a biological memvrane ̎ ˏComm. Biologyˏ2021ˏ4:168.). This... 

Thermosyphon heat pipes are vacuum-sealed two-phase heat transfer devices, commonly called vertical or inclined heat pipes without wicks under the influence of gravity. They comprise a sealed, evacuated tube partially filled with a working fluid. The lower section of the tube serves as the evaporator, where heat input causes the liquid to vaporize. This vapor moves upward to the condenser, where it releases heat and condenses back into liquid form, and the condensed liquid returns to the evaporator by gravity. The adiabatic section, which is located between the evaporator and condenser, is well insulated to allow the vapor to pass through with minimal heat loss. These systems utilize the... 

Introducing the basic concepts of solar desalination systems, improving the performance and efficiency of the solar system under vacuum has been investigated. Further, according to the classification of the types of solar desalination systems, the details of their existing designs have been discussed. The solar desalination system under vacuum is classified into two types of solar systems under natural vacuum and under forced vacuum. The solar system under natural vacuum is divided into one-story and multi-story, while the solar system under forced vacuum is classified into two types, single-effect and multi-effect. Previous studies as well as the most important recent developments in this... 

Although the differences between retail and institutional investors in the stock market can have important effects on key processes such as liquidity and price formation in this market, there are significant differences of opinion about how these differences would affect mentioned processes. An interesting question for financial researchers is how the effects of different groups affect the liquidity of the stock market. Liquidity is defined as the ability to carry out transactions with high speed, low cost and without being heavily influenced by the price. In this research, using 10-year stock information (2012-2022) such as order book, price and volume of transactions, we showed that the... 

Subfloor heating and cooling systems in residential and commercial buildings present advantages from the point of view of comfort conditions and energy saving. In the present work a two dimensional and a three dimensional model for subfloor heating and a two dimensional model for subfloor cooling, using the Fluent software based on the finite volume method were developed. From the point of view of exergy destruction as we may have lower temperature difference between the heating medium and space, we come up with less exergy destruction. To determinate the optimum working conditions of these systems, a numerical model for subfloor heating and cooling is presented. Different methods of... 

The continuous rise in electricity demand and the ever growing power generation in different power networks over the world have caused the short circuit level in the power systems to exceed the operational rating of the installed power devices (including cables, circuit breakers and buses). Replacing these devices with new higher rating devices is an expensive solution. From this point of view, utilizing fault current limiters is an economical solution. Superconducting fault current limiters form an efficient category of current limiters. This type is expected to be studied and used widely in future due to their advantages. In this thesis, the first chapter reviews the superconductivity...