Sharif Digital Repository

Optomechanical systems have attracted considerable attention in the last decade. Such a raising prominence is mainly due to its capability in providing new insight into the quantum behavior of macroscopic objects and exploring the interface between quantum and classical mechanics. Alongside this fundamental quest, cavity optomechanics has many other benefits, ranging from very precise measurements on forces and positions to quantum information processing. In this thesis, we investigate quantum properties of such systems. Particularly, we study cooling of the mechanical resonator toward its ground state and the entanglement between this mechanical resonator and the cavity field. Cooling the... 

By growing the global demand for energy and use the fosil fuel for it by knowing the issue of increase in their resourses؛ it’s important to use new technologies for these energies in an optimum way.
Most of industrial process uses a lot of thermal energy by burning fossil fuel to produce steam or heat for the purpose. One of the most important processes that use energy is refrigeration. After these processes, heat is rejected to the surrounding as waste. This waste heat can be converted to a useful refrigeration by using a heat operated refrigeration system, such as an absorption refrigeration cycle. This can be a useful pattern to improve thermal efficiency of process and reduce its... 

Optomechanical systems have attracted much attention over the last decades, especially as a macroscopic lab for observing quantum mechanical effects . In this thesis , optomechanical quantum memories are studied . In p articularl , we study cooling of the mechanical resonator down to its ground state, which is the necessary condition to obtain a good quantum memory and also explore the limitations of cooling and storing protocols . Quantum state of light can be stored in the mechanical mode of the system by optomchanically induced transparency effect (OMIT) . This effect is formally equivalent to electromagnetically induced transparency effect (EIT) which is seen in an ensemble of... 

In this dissertation, we propose and analytically investigate a scheme for effective three-dimensional cooling of a nanoparticle optically trapped in a Fabry-Perot cavity using multiple cavity modes. By employing active feedback cooling using amplitude modulation of cavity modes, our approach allows to access the UHV regime without the need for any additional means like an external tweezer or a radio-frequency trapping approach. For a set of feasible experimental parameters, we demonstrate that the cooling rates achievable are sufficient to overcompensate recoil heating. Therefore the approach is suited to trap a particle for indefinite times at UHV pressures, where air damping cannot... 

Today, shipping of liquefied natural gas has a considerable share in the global gas trade. Efficient design, optimal operation, and precise control of process variables in the gas liquefaction process decrease energy consumption for LNG production. Understanding the dynamic behavior of a liquefied natural gas unit helps engineers to make the correct choice of controlled variables and tuning controllers. Through a dynamic simulation, this understanding can be achieved. Simulation of a multi-stream heat exchanger, as the heart of the gas liquefaction process, is a challenge of studying this process. In this study, two dynamic models governing a multi-stream heat exchanger in Aspen Plus... 

The annual increase in electricity consumption has led to several problems, including greenhouse gas emissions and global warming. Refrigeration systems are one of the main electricity consumers in the world. Ejector refrigeration systems use waste heat from industries or renewable sources such as solar energy to create the cooling effect. One of the main problems with these systems is the inefficiency of the cycle by the change of the ambient conditions including temperature rise. In ejector vapor compression refrigeration cycles, the compressor increases the pressure to an intermediate pressure. and the rest of the pressure increase is provided by the ejector. These systems can provide the... 

The present thesis aimed to study a novel heat pump integrated humidification-dehumidification (HDH-HP) desalination system. A theoretical outline was proposed for the first time to examine the design and off-design performance of HDH-HP cycles via the compressor characteristics method. In this regard, the variations in heat pump performance were modeled in different operating conditions for a fixed-size system. To fabricate a compact HDH-HP system, an evaporative condenser was designed and used instead of a separate humidifier, heater, and air/water-cooled condensers find in previous HDH-HP systems. Meanwhile, the air dehumidification process in this work directly occurred inside the heat...