Sharif Digital Repository

In this thesis, the physics related to liquid jet injection from injectors with three different crescent-shaped cross-sectional levels into steady and transverse flow were studied. The imaging method in this research was based on shadowgraph, which enables high-speed imaging. With the help of the obtained images, the breakup regimes, including Rayleigh, first and second wind-induced instabilities, were observed for injection into the steady flow. Furthermore, breakup regimes for jet injection into transverse flow, including columnar, columnar-bag, and bag, were also observed. The characteristics of the breakup height in steady flow and the length and height of the breakup along with the jet... 

Optical Communication is a promising technology in access networks because of bandwidth hungry application like videos. So fiber Optic is an important candidate as a media in networks. There are different methods of modulation for transferring data through a channel. Among all, Orthogonal Frequency Division Multiplexing is a method which used in most wired and wireless systems. Recent researches show that OFDM is also a good approach for optical communication.
In this thesis we concentrate on hardware implementation of digital part of an Optical OFDM transceiver. In the first step we ignore the effect of optical channel and design and simulate the transmitter and receiver. After that we... 

Local scouring at the downstream of sluice gates in the erosive beds is one of the main concerns of hydraulic engineers because of the significant damage that it can cause to the hydraulic structures. It is important to control the local scour depth at downstream of hydraulic structures to ensure safety operation of these systems. Many researchers have conducted various studies to predict the maximum depth and diameter of scour hole and develop new methods in order to control this phenomenon. One way to overcome this problem is the use of apron, or non-erosive bed. In order to shorten the apron length or decrease the effect of the... 

In this thesis, the satellite constellation orbit design for regional coverage is investigated. The orbits of satellites in a constellation for Earth observation missions play a crucial role in performance and characteristics of the mission; for example the image resolution, the area of coverage, and the coverage interval. In this thesis the problem is to find the optimal initial orbital elements for meeting the earth observation mission objectives for one or several sites. The cost functions are the total coverage time, the maximum gap time, time average gap, altitude, and number of satellites. The problem is solved in a multi-objective manner for different combination of two of the above... 

Many embedded multicore systems can benefit from a memory hierarchy to bridge the processor/memory speed gap. Embedded systems usually utilize a cacheless architecture to avoid the unpredictable behavior. Unlike caches, scratchpad memories (SPM) are software controlled and hence the execution time of applications on such systems can be accurately predicted. Scheduling the tasks of an embedded multicore application and partitioning the available SPM budget among these cores are two critical issues in such systems. Often, these are considered separately, such a decoupled approach may miss better quality schedules. In this paper, we present an integrated approach to task scheduling and SPM... 

Nowadays marine-tourism industry, especially under water tourism, has become very attractive. Thus, numerous under water vehicles are designed and constructed. The primary objective of the present study is to design an underwater vehicle capable of carrying ten passengers. Tow system is proposed as propulsion system. Due to the high costs, noise and vibrations of existing propulsion systems in medium size vehicles which contradicts the goal of calm atmosphere for passenger, the proposing system seems suitable and pragmatic. Two-part tow system is utilized to enhance the stability of the under water vehicle named Towfish. In this study the structure of towfish is being designed. Then,... 

This paper provides and empirical investigation of individual labor supply of Iranian spouses in a collective framework in which gender ratio and plays a central role in the decision process in household. The data set is taken from the socioeconomic characteristics of panel survey over 2001-2004 and ten yearly headcount of Iran. We have conducted the parameters estimation and hypothesis testing by Semykina, A. and Wooldridge, J.M., (2005) generalized procedure of sample selection in panel data model. Our findings explore that females’ labor supply is affected significantly and strongly by the gender ratio, (total number of males over the females in provinces, both in urban and rural areas).... 

Lateral confinement is a proven method of increasing strength, stiffness and ductility of concrete columns. This is attributed to a created tri-axial stress state in the concrete core due to the confinement resulting in a higher level of endurable deviatoric stress. Plastic pipes are able to create such a confining medium in concrete-filled UPVC tube (CFUT) columns and therefore they can provide the concrete with some benefits of concrete filled steel tube (CFST) column system. Besides, these pipes are cheap, light and they are also easy to handle. Furthermore, they are resistant to corrosion or other forms of deterioration and recyclable and in this aspect, they are... 

The Swaⅿpⅼanⅾ prograⅿ was ⅾeveⅼopeⅾ to ⅽonstrain the effeⅽtive fieⅼⅾ theories that ⅽan be ⅽoⅿpatibⅼe with quantuⅿ gravity. Our ⅾissertation foⅽuses on one of the ⅽonjeⅽtures of this prograⅿ، whiⅽh is known as the Ⅾark Ⅾiⅿension، that preⅾiⅽts the existenⅽe of a ⅿesosⅽopiⅽ fifth ⅾiⅿension of the orⅾer of (mev)−1 . Before exaⅿining the ⅾark ⅾi− ⅿension، however، we introⅾuⅽe soⅿe reⅼateⅾ ⅽonjeⅽtures. Our priⅿary goaⅼ is to stuⅾy the ⅾynaⅿiⅽs of the ⅾark ⅾiⅿension through ⅽosⅿoⅼogiⅽaⅼ observations. To this enⅾ، we begin by proviⅾing a brief overview of 5−ⅾiⅿensionaⅼ fieⅼⅾ theory anⅾ the resuⅼting speⅽ− truⅿ after ⅽoⅿpaⅽtifiⅽation. Next، we ⅾerive the Frieⅾⅿan equations for spaⅽes with ⅿore than...