Sharif Digital Repository

Ilam refinery has three synchronous generator units each with a capacity of 26.5 MVA and two six-phase LCI-fed synchronous compressors, each with a capacity of 8 MW. Generators of Ilam gas refinery have instability issue in case of island operation. With launching one generator unit and then connecting two compressors the instability problem and tripping of the generators appear. Given the importance of this issue, various tests and corresponding measurements in both electrical and mechanical aspects were carried out at the plant in on-grid and island operations to analyze the cause of instability phenomena. The mechanical part of tests analyses the frequency of oscillations and vibration in... 

In today’s modern world, there is an ever-increasing need for developing new ways to provide service in a health system in order to gain the satisfaction of the patients with economically effective methods. One of the challenges faced by a hospital is the allocation of the surgeries to the available surgeans. In this study, a mathematical model is proposed to schedule the operation rooms while considering the daily availability of the doctors, the expense of the operations, overtime hours, and post-operation care. The mathematical programming model is optimized as a stochastic model by using the approach of BIM.
An essential aspect of a hospital system design is the uncertainity of the... 

Increasing energy demand and at the same time, considering exhaustible fossil fuel resources has led to increase distributed generation for reducing energy loss and increasing efficiency of energy systems specially due to technical development on generation systems that meet environmental and energy policy concerns. One of the most important distributed energy technologies is Combined Heat and Power (CHP). CHP is small, high efficiency, low installation time and self-contained electric generation plant that can provide power for household applications, commercial or industrial facilities and hence its applications are overtly increasing. It can reduce power loss and enhance service... 

In many cases, oil and gas extraction from reservoirs due to damage and permeability reduction near wellbore is lower than optimum level and reduces the flow of oil into the well. In fact, formation damage is the collapse of natural condition of reservoirs, In addition to delaying production and increasing costs, it causes early desertification of wells. Well stimulation methods are used to solve this problem and increase production. One of the most effective ways to increase the production of wells is well acidizing. In this study, the acid performance of the fractured carbonate reservoirs has been investigated. In this type of reservoirs, due to the existence of high permeable paths of the... 

The development of technologies such as micro turbines and gas furnaces has been the major driving force towards integration of electricity and natural gas networks in the energy hubs (EH). Besides, the existing power grids are getting smarter by implementing the new generation of information technologies and communication systems. In smart grid, the electricity suppliers can modify the customers’ electrical load consumption by employing appropriate scheduling schemes such as DR (demand response) programs. In this thesis, I consider the S. E. Hubs (smartenergy hubs) framework, in which the customers can use EMS (energy management system) to access to the electricity and natural gas prices... 

Sampling and recovery of a signal is one of the crucial issues in communication systems. In conventional methods, proper recovery is achieved by sampling the signal at the Nyquist rate, which is twice the signal bandwidth. There have been attempts on reducing the required sampling rate, all of which end in rates equal to a factor of the signal bandwidth. Assuming the sparse nature of the signal in hand, which is a reasonable assumption in many real world scenarios, the theory of Compressed Sensing suggests a sampling rate much less than the Nyquist rate. Designing suitable sensing matrices and efficient recovery of the signal from its samples are the two major challenges of Compressed... 

Parallel machine scheduling problems are the decision-making process of allocating limited resources to activities over time. These issues have attracted a lot of attention in the past decades based on their applications in the real world. It can be discussed about the application of parallel machine scheduling problems in computer processing, production lines and multi-stage systems as examples of areas where parallel machine is observed. Most of the research on parallel machine scheduling has focused on the optimization of a single criterion such as total or average task completion time, total completion time with different weights, sum of penalty or tardiness penalty, total number of... 

High voltage power supplies have a wide range of applications, and due to their high cost, it is essential to monitor their condition to predict potential failures and prevent significant losses. The most common cause of power supply failure is the wear and tear of its components. However, these components can be replaced before they wear out completely to prevent the failure of the power supply and, consequently, avoid damaging the load. Estimating the lifetime of power supplies is crucial because it allows for scheduled maintenance and helps prevent significant problems in power supplies. By estimating the lifespan of a power supply, one can anticipate when it may fail, allowing for the... 

Dense underflows are continuous currents which move down slope due to the fact that their density is heavier than ambient water. Driven by density differences between the inflow and clear water in the reservoirs, the density current plunges the clear water and moves on the bed. While density currents flowing on a sloping bed, the vertical spreading due to water entrainment plays an important role in determining the propagation rate in the longitudinal direction. These currents are similar to wall-jet currents according to structure of the flows but are complicated relative to wall-jet currents due to the existence of density difference. Characteristics of the density current sometimes are...