Sharif Digital Repository

Using Aspen Hysys to simulate burners and furnaces has been the focus of several studies in recent years. According to the studies and investigations carried out in the field of optimal design of the furnace, heating the air is one of the possible tasks to improve the performance and increase the efficiency. According to the obtained results, by adding air preheat, the efficiency increases from 92% to 96%. Also, to validate the simulation, two furnaces from Sepahan Oil Refinery furnaces were simulated in the field of oil production, which were simulated with an error of less than 1% in duty calculation, and according to the general results obtained, adding air preheat can increase the... 

The objective of this research is to introduce a new comparative performance measure based on seismic fragility curve of structures. This measure is used here to investigate the efficiency of viscous dampers on the behavior of a weak mid-rise steel structure. Viscous dampers are commonly utilized to reach purposes such as decreasing the risk of the structure failure and restoration costs, weight reduction, and seismic rehabilitation of existing structures. These systems cannot be satisfactorily investigated using static loading concepts, and in order to achieve optimum design, conducting a nonlinear dynamic analysis is usually the most reliable procedure. Therefore, 5-span 12,15 and 18 story... 

Wastewater treatment plants play an important role within the urban water cycle in protecting receiving waters from untreated discharges. In the developed and developing countries, Energy consumption of these units are 3 and 5 % of the electrical energy demand, respectively. As far as sustainable development is concerned, not only the reduction of WWTP’s energy consumption is mandatory, but also these units should produce energy. To this end, several techniques are available namely: energy audits, replacement of equipment and improvement of process efficiency. Moreover, Energy can be generated by converting biogas -from anaerobic digesters- to heat and power. Todays, Biogas is well-known as... 

The purpose of this research is the conceptual design of an aerial robot that has the ability to reach different locations without changing its horizontal attitude. The main missions of the aerial robots are monitoring and delivery, in which none of them requires the robot to leave its horizontal attitude. The main task of the robot is to deliver the goods to the specified points. In order to do this, it must have an appropriate container for carrying the cargo, high safety to prevent damage to the cargo and individuals, the ability to carry out missions when one of the subsystems exits, and the appropriate flight speed for Deliver cargo to the customer as fast as possible. All of the... 

The steam turbines share a significant part of Iran's electricity production. Evidently improving the performance of these steam turbines will improve the performance of power plants and enhance the capability of power production in Iran. Since the behavior of steam turbines is highly nonlinear and that it is affected by various factors, it is difficult to determine the optimum operating conditions for each turbine in specific unit of a power plant. In addition, it is very difficult to model the turbine behavior based on the mathematical equations. Fortunately a large amount of information is collected and stored annually by the data-processing systems in each power plant. These collected... 

Nowadays, the structural health monitoring is considered as an essential element in improving the performance of the structures. The role and importance of the issues in this area have been reached to the point that different ideas and policies are developed for the safety margin over the useful life of the structures. To analyze more accurately, a real model of a turbine blade is required. This issue would be taken into more consideration when the scale of the turbine gets larger. Changing of the design philosophies over time results in effective changes in the design process and maintenance procedures. Any single of these inspections has different importance according to users' demands. In... 

I investigate methods of integrating prior hierarchical structure into hierarchical portfolio optimization methods. My contributions to the literature are forming a prior hierarchical structure based on investors' priorities and generating a unique representative distance matrix, which can be used as an input to other portfolio optimization methods too. In addition, I use SIC and GICs industry classifications as priory information for S&P500 companies and use them as a complementary input to the Hierarchical Risk Parity model and Hierarchical Equal Risk Contribution and compare the resultant portfolios' performance with (López de Prado, 2019)’s method of integrating prior information and... 

In this study, we seek to evaluate the three factors of knowledge level, the rate of use and attitude of exporting companies to the services provided by Iran Trade Promotion Organization. A questionnaire was used to collect information and data from 68 active companies in different industries of the country. Questions are about the 8 support packages officialy provided by the trade promotion organization to help exporters. In this research, we first studied the importance of the subject and the theories presented in this regard, and then we examined the similar studies conducted in other countries. Afterwards, we describe the tools used to collect information and present the results of the... 

Content delivery networks play a significant role in improving the quality of internet services by placing the necessary content closer to users on servers. Currently, over half of internet traffic is delivered through these networks to end users. The efficiency of a content delivery network depends on various parameters, including the type of requested content, workload distribution methods, network topology, routing algorithms, caching policies, network server configurations, and resource allocation (shared or dedicated hardware resources). Additionally, the requests made to a content delivery network vary based on the type of service and even the time of day, making optimization a... 

Online social services and stores has become more popular in recent years . With the growing number of products and services available in these online stores and websites , recommendation systems play an important role in predicting which products and services are good for each user so that they can buy the product they need or use the online services they want without wasting their time to find the right ones . We propose a method called Temporal Socio-Content Poisson Factorization (TSCPF) which aims to recommend the most probable document to be read by each user at any given time . We model users’ behaviors and interests by using temporal point processes to capture temporal dynamics of... 

Appearance of CUDA architecture results in GPU introduction as a suitable platform for parallel processing. Massive usage of GPGPUs in various applications forces the manufacturers to produce this processor with different configurations based on their application demands. But always the design approach observes a ratio between processing capability and bandwidth of GPGPUs. In this way mostly in all GPGPU series the bandwidth increases with growth of GPGPU processing power. At first glance this ratio seems reasonable because more process needs more data. However this approach does not pay attention to the behavior of a wide range of workloads which do not need such a bandwidth. Mentioned... 

Nowadays, with the advent of Autonomous Vehicles(AV), Researchers in different areas focused more on this type of vehicle. Research shows that autonomous vehicles are faster and more precise than Human-driven vehicles(HDV). So if all the users in a road use autonomous Vehicles, the road’s capacity increases; this Thesis develops a mathematical approach for designing AV exclusive lanes for a time horizon in which there are two types of AVs and HDVs on the road. Considering each type of vehicle’s relative performance for an OD pair in the given year, the demand for that OD pair for the next year calculates with a diffusion model. Designing AV exclusive lanes problem is formulated in a bi-level... 

User comfort in wearable robots and precise limb tracking of the robots' links can be considered as general and significant indicators of the robots' performance. On the other hand, due to the kinematic mismatches between the human body and conventional wearable robots, which often occur due to various reasons such as the kinematic differences between the body and robot joints (e.g. the knee joint), it seems unlikely to achieve a robot in which user's limbs comfortably follow its link without tracking error. In this study, in order to evaluate and improve the performance of the robot, two performance indices: limbs tracking error index (TEI) and user discomfort index (DI) were introduced,... 

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... 

Today, spark ignition internal combustion engines make up a large percentage of passenger car engines, so their performance improvement is important. Turbocharging of these engines, although is an appropriate method to enhance their specific power and improve their specific fuel consumption, but it has big problems such as the possibility of knock and increasing the NOx emissions in the engine. In this study, resolving these problems is intended by controlling the engine inlet charged air temperature to improve performance of the engine. For this purpose, the investigations are conducted experimentally as well as numerically. The experimental studies are carried out on a turbocharged... 

Alzheimer’s disease (AD) is a neurodegenerative disease which results in synaptic depression and complete destruction in neurons in the final stages. Many pathogenesis has so far been attributed to AD but the most commonly explained pathomechanism is based on the amyloid cascade theory which results in formation of amyloid beta plaques outside and hyper phosphorylated neurofibrillary tangles of tau protein inside the neurons. One of the most well-known symptoms of AD is the disability to learn and form new memories and transform them into long term memory. The most commonly studied mechanism in memory formation, is the “long term potentiation”. Although many mechanisms and molecules are... 

Optimisation is ubiquitous and essential in almost all areas of engineering and computer science for the design and analysis of efficient systems and algorithms. Indeed, many engineering problems can be cast as optimisation problems, in which a decision must be made upon certain control parameters in order to maximise revenue or minimise an incurred cost in designing a system. Whereas deterministic optimization problems are formulated with known parameters, real-world problems almost invariably include parameters which are unknown at the time a decision is made. Stochastic optimisation is the approach for modelling optimization problems that involve uncertainty, and it has attracted a lot of... 

Fault-tolerant ability is more subjected in Cascaded H-Bridge Multilevel Inverter due to its high-power medium-voltage applications and large number of semiconductors switches used in its structure. In this thesis, the goal is performance improvement of Cascaded H-bridge Multilevel Inverter under faulty conditions. Since to achieve the post-fault ability two steps; fault detection and post-fault control are required, both steps are considered in the improving process. In this dissertation, first operation of Cascaded H-Bridge Multilevel Inverter in normal and faulty condition is surveyed. Then, the conventional fault detection methods are mentioned and post-fault control methods are... 

One of the main goals in large projects with multiple contractors is to reduce costs in various processes. The complexity of a large project, which is mainly due to the complexity of activities and the existence of interference between different phases and the lack of transparency of activities, can be added to the multiplicity of contractors and the difficulty of proper interface management.As regards that large projects with a large scope of work, have to use several contractors and this issue has a direct impact on increasing project costs, large project management becomes a major challenge that the application of appropriate knowledge, improving processes and skills and tools can play a... 

In many cases even high-quality products cannot satisfy the customer needs and this leads to having a lower share of the market. To achieve this purpose, customer satisfaction and robust design are regarded simultaneously to achieve a better quality. Balance Score Card (BSC) is proposed as a technique that could potentially has a great improvement effect on customer satisfaction. Moreover, with a non-linear programming (NLP), a novel method for integrating RSM and BSC have been proposed to accede robustness in design. The opinions of the customers are regarded in every system design, parameter design and tolerance design. To validate the applicability of the proposed approach, the approach...