Sharif Digital Repository

Networks and the epidemiology of directly transmitted infectious diseases are fun-damentally linked. The foundations of epidemiology and early epidemiological models were based on population wide random-mixing, but in practice each individual has a finite set of contacts to whom they can pass infection; the ensemble of all such contacts forms a network. Knowledge of the structure of the network allows models to compute the epidemic dynamics at the population scale from the individual-level behaviour of infections.Motivated by the analysis of social networks, we study a model of random net-works that has both a given degree distribution and a tunable clustering coefficient.We consider two... 

large ships should only make very small horizontal movements at the berth for efficient loading. This is especially a concern in ports facing the open ocean directly, where high swells at sea can cause harbor oscillations and low-frequency surge motions of the ship. A developed mooring unit, the MoorMaster, which replaces conventional mooring lines is addressed here. The hydraulics of the system have a strong reducing effect on the motions of the moored ship. Measurements have shown that the surge motion of container ships was reduced from an amplitude in the order of 1 metre to an amplitude in the order of 5 centimetres, by using MoorMaster units. In here MoorMaster action is divided to two... 

Circuit model quantum computing, provides a powerful tool that allows humans to process information faster. Excessive noise and its impact on quantum systems which can lead to data loss are major obstacls in accessing quantum computers, since the systems proposed to make quantum computers are indeed open systems, noise can cause data loss. Therefore, the achievement of quantum computing, has been delayd. One of the most effective ways to neutralize this noise is to use a geometric phase to make evolutions. Holonomic quantum gates utilize the geometric phase to implement the noise resilience gate. In this thesis, we intend to use a composite optomechanical system, consisting of two optical... 

The per capita income and welfare levels of countries around the world vary significantly from each other. Identifying the factors that lead to differences in the per capita income of countries as well as their welfare levels is a major concern for economists. Studies conducted in this field indicate that one of the main sources of these differences is the significant disparity in the total factor productivity (TFP) across countries. Suboptimal resource allocation is one of the most influential factors affecting TFP in countries. The primary importance of investigating misallocation in the Iranian economy is that, in line with the decrease in economic growth, the growth rate of industrial... 

The application of membranes for separate of particles in mainly microbial flacs , are fast growing in biological treatment systems. Membrane bioreactors are now considered as one of the major new processes in wastewater treatment. However , membranes are expensive and costly. This study is carried out to test an innovative , locally made filters for separation of flocs in an MBBR reactor. This innovative filter is replacing a traditional settling tank. This type of filters is made very cheaply and has important advantages in installing and operation. Experiments were carried out in a laboratory scale MBBR unit. A filter unit consisting of 3 innovative filter tubes were placed and the... 

In this thesis, the optimal trajectories of a spacecraft in the binary asteroids system is studied. The objective functions of optimal trajectories in these system are the maximum coverage of the asteroids surface and minimum time and fuel consumption. For this purpose, the dynamic of binary system is modeled. The binary system of 1999 KW4 is selected as a case study. The ellipsoid-sphere model is a good approximation for the case of this study. In this model, the asteroids orbit in a circular orbit around each other in a spin-spin-orbit resonance configuration, in which the asteroids’ rotational velocity is equal to orbital mean motion. Then, the equations of motion of the spacecraft as the... 

The distinction between SOEs and private firms in access to loans is essential from the viewpoint of policy-making. This distinction is more crucial when we know that the difference is caused by factors other than natural market forces and has emerged merely by government ownership. In this paper, we investigate a unique intervention in privatization and identify the causal effect of government ownership on access to loans. In this respect, we study Sahamedalat in Iran by using DID approach and estimate the effect of giving up the treatment firm's cashflow right on the amount and composition of the loans. The results show the intervention significantly decreases the long-term loan of the... 

Privatization is one of the most important economic reform policies of the 1980s and 1990s, and it has been widely studied. Many researchers have studied the difference between public and private companies from the perspective of productivity and performance. Due to the different implementation methods of this policy, different consequences are expected. In this research, the causal effect of government ownership on the productivity of companies is investigated. In this regard, using the difference-in-difference method, we investigate the Equity Share policy and measure its effect on the level of productivity of companies and their growth. The results show that the implementation of the... 

Friction drilling or flow drilling is a method of making holes in metal sheets, in which the material is pushed with the aid of heat from friction. This procedure allows making holes in sheet metal, with a sleeve formed as the hole is created. This sleeve is then threaded and used as the nut, thus eliminating the need for access to the interior faces of hollow steel sections. On the other hand, with the development of advanced manufacturing techniques, larger and thicker hollow structural sections are becoming more popular in mid-rise and multistory structures. onsequently, flow drilling can be considered as a viable alternative for traditional drilling techniques, where the material is... 

One of the most important methods for recycling of spent Li-ion batteries is acid leaching that various parameters affect it. In this work, influences of effective parameters on the percent of cobalt and lithium recovery with application of design of experiments (response surface methodology-central composite) were investigated and then cobalt nano oxide as the by-product synthesized by pulsing lectrolysis. In the first Phase, effects of parameters such as sulfuric acid oncentration: 2-6 molar, hydrogen peroxide volume percent: 5-10%, S/L ratio: 20-50 g/L and temperature: 50-80°C on cobalt and lithium recovery were investigated and finally an adequate model presented. For all experiments,... 

The financial depth in Iran has decreased since 2008 and simultaneously the interbank rate has increased. In addition, researches show that the bank health has decreased over the same period. This research investigates to find evidence for the existence of the relationship between the bank health indicators and its lending power. In this regard, the balance sheet data and financial statement data of the Iranian banks during 2007 to 2014 have been investigated and the effect of the bank health indicators on their lending power studied at the normal conditions and sanction periods. In this research like Kashyap and Stein 2000, and Gambacorta and Marques2011, the bank lending channel consider... 

In the banking and macro-financial literature، banks are modeled as financial intermediaries who give loans to the borrowers from their deposits. In these models، deposits are created from the accumulation of real goods. Besides this view، which is used more in the academic environment، others who are most practical، describe banks not intermediaries، but credit creator which do not need deposits to pay loans. In this research، we use credit creation concept in a Neoclassic environment that the central bank’s monetary policy is fractional reserve to answer this question that if banks could create credit for firms based on its future income، while firms have CIA constraints، how do economic... 

Related Lending is defined as banks making loans to firms with which they have some kind of ownership association. On one hand, this practice can help diminish asymmetric information between bank and firm which results in a more efficient allocation of bank’s resources. On the other hand, it may lead to the banks’ transferring resources to their related firms inefficiently, without meticulously assessing the risks involved. This paper is focused on the effect of the relationship between bank and firm in their ownership structure, on the loan provision. I have gathered a unique dataset of private and privatized banks and also private firms active in Iran’s stock market, which covers the...