Sharif Digital Repository

Considering the advantages and disadvantages of reported micropumps, we aimed to introduce a novel idea to diminish the disadvantages and promote the advantages of Magnetohydrodynamic (MHD) micropumps. This novel idea operates based on a mercury slug rotation in a circular microchannel. This cyclic motion of the mercury slug which is similar to a piston, push the fluid in the microchannel and pump the flow. However, to bring this idea into the practice, it must be integrated with a specific valve. Fluid has not to go through this specific valve. In contrary, mercury slug has to pass across this valve. These two specifications must be considered during the design process of the valve. On the... 

In this thesis CCM/CVM operation and modeling of the Sheppard-Taylor topology is reviewed and a predictive control strategy is applied for a Sheppard-Taylor-based power factor correction (PFC) rectifier. Compared to conventional boost or buck boost PFC’s, this topology allows a better current tracking at the AC side, with a relatively reduced voltage at the DC side. Consequently, the high frequency AC filters required by the buck PFCs are avoided, and the voltage stresses on the boost switches are significantly reduced. Furthermore In predictive control strategy the duty cycle required to achieve unity power factor in a half line period can be calculated in advance. The main advantage of... 

The problem of developing optimal pricing and inventory allocation strategies has been extensively studied over the past two decades. However, most of the literature in this area assumes that customers are myopic price-takers, and do not respond to firm pricing strategically. In this study, we present review on a class of problems that consider a firm selling a finite number of items over a finite time horizon facing stochastic demand and a group of customers who act strategically by timing their purchases. We first review the optimal purchasing policy for the customers, and pricing policy for the firm that is the best response policy to the customer’s strategic behavior. Then we present a... 

Flying has fascinated mankind for ages. Nowadays, planar actuators are performing the same task as that, once a dream, of a flying magic carpet found in Persian mythology. Magnetically levitated planar actuators (MLPAs) consist of two parts; a moving part, and a stationary part. In most applications the moving part which is an array of permanent magnets (PMs) produces a magnetic flux density in the air-gap, and the stationary part, an array of current carrying coils, produces force and torque when it is exposed to the magnetic flux of the PM array. These actuators have been utilized in industry in applications where precise positioning is important. In recent years however, they have found... 

Lameness in dairy cattle is a crucial welfare issue in dairy industry, and over the years scientists are attempting to present a detection method. In recent years it is attracting more attention to make the identification and discrimination of sounds and lames systematic and automatic. Right now, the most hopeful results have been obtained through the measurement of Ground Reaction Forces (GRF) of hooves, and analysis of load distribution between four legs, which seems applicable for wide use in dairy industry. However, the accuracy, validity, and reliability of discrimination is still far from an acceptable point, that is because of a great lack in understanding quantitative effects of the... 

One of non-cooperative illuminators recently considered for passive radar application is the DVB-T signal. Its thumbtack ambiguity function beside the constancy over time makes it very desirable. But there are some ambiguities in its ambiguity function that can not be neglected. In this paper, after studying the reasons of the ambiguities we propose some processings to remove them. It is shown that for removing the ambiguities, it’s sufficient to filter out continual pilots and equalize scattered pilots. The results show that an ambiguity function relatively without ambiguities will be obtained. A method for compensating the target’s range migration-that results in processing gain decrease... 

This existing research has been conducted to reach quick evaluation instructions to pipe earthquake damages in the piping systems inside the industrial complexes. In the old complexes of such kinds there are cases where field inspections and quality evaluations are urgently required subject to peculiar conditions affecting each piping system inside the units and in certain cases subject to lack of access to the as built-drawings. However, so far any definite instruction hasn’t been available for a quick evaluation of likely damages in piping system: all because of various pipe types, complexity of pipes geometry, different temperatures and pressures in different sections. In this research... 

In this dissertation we discuss various results presented in the literature on single user channels with causal or noncausal side information and multiuser channels with side information such as multiple access channel and broadcast channel. The Series Relay Networks (SRN) with delays, with and without channel state information (CSI) are investigated from an information theoretic point of view. For SRN with unlimited look ahead where the relays can use the whole received block to encode, upper and lower bounds on the capacity are derived which are tight for the degraded case. For SRN without-delay where the relays have access to the present received symbols in addition to the past symbols,... 

Pregroups as a mathematical structure, are replacement for Lambek's type caregorial grammar which much used in Computational Linguistics. Because of computational and logical properties of pregroups, we can use them as strong tool to analyse the sentence structure of many natural languages. This kind of analysis has been done for English, French, German, Polish, Italian, Arabic and Japanese. In case of Persian language, analysis of simple and compound sentences structure with simple tense verbs and explicit subjects and objects has been studied. In this M.Sc. thesis, we will extent analysis of Persian sentence structure to sentences with compound tense verbs and implicit subjects and objects... 

Data envelopment Analysis is a non parametric technique which estimates the efficiency of a decision making unit in compare with others. In correspondent literature this unit’s Inputs and outputs are often assumed to be deterministic, but in recent years different approaches which viewing the data as non deterministic are presented. In this study we propose an algorithm for determining the stability region of a DMU while we assume other DMUs’ data are fixed. This algorithm is based on changing the reference set of the under investigation DMU. In fact applying these changes make the DMU move toward other DMUs’ efficient frontiers and by using this fact it is possible to determine the... 

Empirical results in this research show that oil abundance in an economy tends to increase income inequality. Three mechanisms: Trade, civil liberties and imperfections of financial markets can explain this empirical finding, with the first being an alternative explanation for the Dutch disease. Besides, due to the influence it could have on parents underestimating the future costs of their children and because of the rents it produces, Oil abundance could reduce the opportunity cost of having children which results in a higher fertility rate. Moreover, empirical results confirm the negative relation between inequality and growth through the fertility mechanism. Therefore apart from... 

The enzymatic transesterification of castor oil with methanol in a solvent free media is carried out using lipase catalyst. The influence of several operation conditions on the production of biodiesel was analyzed i.e. the amount of enzyme, molar ratio of methanol to castor oil, reaction temperature and reaction time. It is observed that with increase in molar ratio, reaction time and enzyme amount, the amount of product (biodiesel) increased. When reaction temperature increased, the amount of biodiesel increased firstly and then decreased. The optimum conditions for the reaction were as follows: enzyme amount 300 mg, molar ratio of methanol to oil 9:1 and temperature 55°C. The maximum... 

Redundant number systems provide for carry-free arithmetic, where the result of arithmetic operations is achieved, in redundant format, without the need for latent carry propagation. However conversion of the result to a conventional nonredundant representation, always, requires carry propagation. Therefore, efficient use of redundant number systems is feasible when a series of arithmetic operations is to be performed before the need arises to obtain the result in a nonredundant representation. Redundant number systems have been used in several special purpose integrated designs (e.g., DSP applications) and also as intermediate number representation in complex arithmetic operations... 

According to Haldane Conjecture Antiferromagnetic Heisenberg Spin Chain with integer spin has an energy gap, and exponential decay of correlation functions , while half integer spin chains are gapless with algebraic decay of correlation functions. A spin chain with two types of spins and Heisenberg interaction shows a mixture of both types of behavior. A ferrimagnet which is composed of two spins (S, s) has two bands of energy, the lower band is gapless and ferromagnetic property while the upper one is gapful with antiferromagnetic behavior. In the present work we have studied the anisotropic ferrimagnet in the presence of a transverse magnetic field. We have shown that the spin wave theory... 

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... 

In this study, the effects of different corrosion inhibitors on the corrosion of aluminum alloy which is used in the cooling systems of automotive industries were investigated. Also a comparison between the corrosion behaviour of the mentioned aluminum alloy with and without any galvanic connection to 5 different metals consist of solder, stainless steel, mild steel, brass and copper was done. The corrosion rate became more by establishing galvanic coupling. The base solution was ethylene glycol and water which is the base part of all antifreeze compounds. The tests were done at high temperature about 88ºC. Two different industrial corrosion inhibitors were examined in these conditions.... 

Achieving the required Quality of service (QoS) is a challenging task in the emerging next generation networked multimedia applications. Providing QoS guarantees becomes even more challenging when you add the complexities of wireless and mobile networks. An important aspect of wireless networks is their dynamic behavior. Especially when we need to transmit multimedia data over wireless networks, this problem becomes more significant. Live video with large end to end delay is meaningless and very low quality video is not satisfying. In recent years, a number of Protocols for providing guarantee of service are presented in the literature. These techniques include data link layer QoS schemes,... 

This Project describes a new model for Inventory management in Supply Chain (SC), based on Fuzzy Set Theory and Echelon Inventory model. In today’s changing market, managing the Supply chain inventories, especially for the new product becomes more complicated and uncertain than before. This work provides a new approach to model uncertainties involved in supply chain management using fuzzy set theory. For achieving a more realistic model, Echelon Inventory is used as the base of integrated supply chain inventory model. In proposed model, some of input parameters like demand, production parameters, transportation time between inventories, and some of variables like lead times are described as... 

Recently, computer scientists and economists have defined many joint problems and cooperate widely in various areas. Importance of this interconnection is clear for everybody, now. New works have been conducted, nowadays, to use the daily - increasing web-based social networks in viral marketing for improving companies profits. The main problem which is proved to be NP-Complete in this context is about discovering k most influential nodes in a network. In this dissertation, we generalize the problem to a group-based version and we we use group-based advertising to achieve our main goal. A new algorithm called Group-Based Diffusion technique is proposed in this thesis for solving this problem...