Sharif Digital Repository

The potential of phase change process in liquids at microscale has been a favorite for the scientists to fabricate this type of micropumps. To hold unidirectional flow in microchannels usually nozzle-diffuser arrangement is used. Due to the existence of difference in pressure drop in the nozzle and diffuser sections, one can see unidirectional flow through diffuser direction. The objective of this article is to analyze analytically the thermo-hydrodynamic behavior of the Isopropyl Alcohol (IPA) bubble of a phase change micropump. Considering the simultaneous effects of hydrodynamic and thermal characteristics of the bubble in the bubble generation chamber, and temperature-saturation... 

Porous burner technology has many advantages in comparison with conventional burners such as higher burner thermal performance, lower pollutants emission, high power ranges, fuel flexibility, compact geometry and higher turn down ratios. These kinds of burners are made of preheated porous combustion zone and combustion porous zone that have different thermophysical and geometrical properties. In this work, the transient one-dimensional multi-step premixed laminar reacting flows in a two-stage porous media burner have been investigated. The combustible mixture is considered H2-Air (9 species and 19 reactions) and CH4-Air (22 species and 49 reactions). In porous media, without lateral wall... 

In this research we investigate the effect of demand disruption on coordinating a supply chain with one manufacturer and one retailer competing with a manufacturer. For this purpose we consider two kinds of demand function: 1) a demand function which determines the demand deterministically and 2) a demand function with a random factor which determines the demand stochastically. Also we assume that in competition between retailer and competing manufacturer, retailer possesses more power than his rival in the market. In order to study the effect of demand disruption on coordinating the supply chain, first we consider coordination without demand disruption by using linear quantity discount and... 

Integration of radio transceivers results in developing low power low cost wireless systems and allows delivery of multimedia contents to battery-powered mobile terminals. Portable reception of digital video for hand-held devices is one of the applications, for which, some telecommunications standards have been developed in the recent years. This research deals with the integrated implementation of the radio frequency parts of the digital video receiver, especially the frequency synthesizer. The key aspects of the digital video reception system are the required signal to noise ratio, which is relatively high, wide band input signals and strong interferers in the receiving band.
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Hydrocyclones are used for separating different materials from liquids in a variety of applications. Compactness, efficiency, reliability and low maintenance costs are their noteworthy characteristics. Dewatering and deoiling hydrocyclones used for refining crude oil or oily waste water in offshore platforms are examples of liquid-liquid hydrocyclones. Separation process in hydrocyclones is based on the fact that swirl flow induces a centrifugal force and leads to separation due to density difference. The density difference in liquid-liquid mixtures is smaller than solid-liquid types and trying to separate one liquid from another takes much more effort than the other type. Increase of... 

Energy conversion and storage as well as life sciences are among the areas of our daily life. Interest in carbon nanomaterials for energy storage systems such as supercapacitors has enormously risen due to their attractive electrical conductivity, chemical inertness, and charge storage capacity. Producing these nanomaterials with a simple, scalable, and cost-effective method is the major problem for commercializing them. The reduction of graphitic oxide is a versatile procedure to prepare 3D graphene. Despite many green methods, the dynamics behind ultrafast thermal graphitization have remained elusive. Here, we demonstrate an effort to understand the graphitization mechanism of graphitic... 

Influence tactics are methods which people use to influence others. These tactics may have different effect due to their sources of power, context, etc. On the other hand, if others perceive somebody authentic while he/she is using a tactic, it can be more effective. Through in-depth interviews with the members of the government and private sector dialogue council in Yazd’s Chamber of Commerce, this research examines the tactics of rational persuasion, appraisal and ingratiation. It seems that knowing the person who is arguing, the validity of his argument, emotionalizing the meeting atmosphere and some side factors like body language are effective in the perception of authenticity from that... 

Since the seminal work of Modigliani and Miller, the basic question of whether a unique combination of debt and equity capital maximizes the firm value, and if so, what factors could influence a firm’s optimal capital structure have been the subject of frequent debate in the capital structure literature. Empirical work in this area has lagged behind the theoretical research, perhaps because the relevant firm attributes are expressed in terms of fairly abstract concepts that are not directly observable and furthermore capital structure decision-making is even more complicated when it is examined in an international context, particularly in developing countries where markets are characterized... 

This project is about crest triangular weirs. The discharge is a function of triangular angle and head of the water. There are so many projects that is about the effect of various parameters on the discharge of weir. In some places we can not use just one symmetric weir so we have to use multi weirs. Because of the lack of information in multiasymmetrical weirs, the goal of this project in studing multi triangular weirs in laboratory. We used the civil engeneering department of sharif university chanel that is 148 cm in width and 40 cm in height. In this project we used three 60, two 90 and two 45 triangular weirs that instaleed singular,double and triapple in various position in width. In... 

The prediction of deposition efficiency of submicron particles in the pulmonary alveoli has received special attention due to its importance for drug delivery systems, and for assessing air pollutants health risks. In this work, the pulmonary alveoli of a healthy human are idealized by a three dimensional honeycomb like configuration and a fluid-structure interaction analysis is performed to study the normal cyclic breathing hydrodynamics. A viscoelastic model is used for the mechanical behavior of alveolar wall tissue. In contrast to previous works in which the inlet flow rate is predefined, in this model a negative pressure is imposed on the outside surface of the alveolus which causes air... 

Price manipulation can lead to lack of transparency and impair proper functioning of financial markets. On the Tehran Stock Exchange, there is ample anecdotal evidence that some blockholders try to manipulate the price before the block transactions to change the share price significantly. In this paper, we provide empirical evidence that in intergroup block trades, blockholders tend to buy shares before the trade date or engage in round-trip transactions to increase the block shares price. No such evidence is found in intragroup transactions and other explanations such as market reaction to a change in corporate ownership seem more plausible than price manipulation. In addition to the... 

Thermopneumatic micropump is one type of positive displacement micropumps, which has many applications due to its relatively large stroke volume, low working voltage, and simple fabrication in microscale. In this paper, a numerical study of heat transfer and fluid flow in a valveless thermopneumatically driven micropump is presented. For rectifying the bidirectional flow, a nozzle and a diffuser are used as the inlet and outlet of the chamber. Since the fluid flow is induced by the motion of a diaphragm, the numerical simulation includes fluid structure interaction, which requires applying a dynamic mesh. The domain of solution is divided into two sections; the actuator unit, which contains... 

These days, according to increasing requirement to the applications of clean rooms in industries in and within the developing industry of computer, positive indicators that show a real need to a compere comprehensive study and research about the Clean rooms, in oder to predict the distribution and dispersal of the particles. Correct determination of indoor airflow and particle concentration distribution results in new standard development for Clean rooms. As computational fluid dynamics has become a powerful tool for indoor airflow studies, in this research, influence of effective parameters on the flow and concentration distribution in clean rooms has been... 

In order to safe design and optimize performance of industrial systems which work under two phase flow conditions, it’s often needed to categorize flow into different regimes. In present work the experiments of two phase flow were done in a large scale test facility with length of 6m and 5cm diameter. Four main flow regimes were observed in vertical air-water two phase flows at moderate superficial velocities of gas and water: Bubbly, Slug, Churn and Annular. Some image processing techniques were used to extract information from each picture. This information includes number of bubbles or objects, area, perimeter, height and width of objects (second phase). Also a texture feature extraction...