Sharif Digital Repository

This project focuses on the design of fuel drop tanks for airplanes that add minimal drag and positive lift to the flying object. This will obviously effect the stability and dynamic performance of the airplane. To reduce adverse dynamic effects the tank was divided to several segment with a special emptying sequence. The add-on tank has to have no interference with the object existing systems and require minimum structural changes in the object. Several designs were proposed and the one gaining highest marks was selected. The flow field and the dynamic behavior of combined vehicle and drop tanks were studied using FE simulations. The result shows that adding a drop tank with optimized... 

Gorgan Bay and Miankaleh Wetland have been exposed to various environmental risks in the past years due to the decrease in the Caspian water level and the subsequent decrease in the water level of these water bodies. 2 channels, Chapgoli and Ashuradeh, are the only ways connecting the Gulf with the Caspian Sea. If the water level of the Caspian Sea and the Gulf continue to decrease, these 2 channels will be completely blocked and the connection between the Gulf and the sea will be completely closed. Due to the low depth of the bay and high evaporation on this water body, the blockage of these 2 channels will eventually lead to drying up of the bay or changing the flora and fauna of the area.... 

Washing a dead person’s body and dressing the corpse prior to burial is an act of love and necessity in many religions. Since the deceased loses all bodily functions at time of death, cleaning the body to eliminate odors is generally a hard and unpleasant task for many to perform. It has also been reported that tens of thousands of microbes are present on every square centimeter of a human corpse which is always a health risk to the persons performing the task. Among Islamic nations, preparation of the corpse is usually carried out in washing rooms (Ghassalkhaneh) of cemeteries in large cities. This preparation consists of two important operations namely as washing of the corpse (Ghosl)... 

In recent years world countries faced with the ageing aircraft fleet problem which increased the repair and maintenance costs of these aircrafts. The non-destructive inspection methods are common inspection methods of old aircrafts. To do this, the aircraft must test with a certain time scheduled inspection programme in a hangar. This method not only increased the repair and maintenance costs but also affects the flight schedule. To overcome this problem, the structural health monitoring can use to online monitoring the structure and when it needs for repair, the aircraft send to hanger. So, repair and maintenance costs minimize while the flight schedule less affected. One of the structural... 

Wireless LANs are becoming widespread in enterprises due to extensive usage of mobile devices and appearance of bring-your-own-device policies. However, mechanisms common in home WLANs are not sufficient for managing lots of access point and clients in an enterprise WLAN and WLAN controllers which are used in enterprises nowadays are limited to a fixed set of commands operated from a CLI and the source code is not changeable. Also, their effectiveness can be harvested alongside access points from the same vendor. Thus, dynamic high level programming for whole network configuration is an absolute need in this changing business environment and Software-defined Networking (SDN) will empower us... 

Position sensors are essential in the control of moving systems. One of these sensors is the Variable Reluctance Resolvers(VR) which are used in the control of permanent magnet motors(PM) due to their simple and robust structure. Variable Reluctance Resolvers can be built in inner/outer stator configuration. Although most commercial Variable Reluctance Resolvers have outer stator and inner rotor configuration, the manufacturing process for inner stator and outer rotor resolvers is much simpler than that of outer stator ones. In this thesis, an analytical model based on the Magnetic Equivalent Circuit(MEC) is initially presented to predict the performance of the outer rotor Variable... 

Diesel engines have widely used in past hundred years. During this time costly and extensive researches have been done to improve engine performance, which is going on. Important issues of these engines are higher specific power and efficiency and lower specific fuel consumption and pollutions formation. One of the best methods for engine performance improvement is matching a convenient turbocharger on engine. A turbocharger increases the engine air mass flow rate by increasing the inlet pressure and density. Due to increase of fresh air mass flow rate, fuel mass flow rate and power would increase. The aim of this research is to choose the convenient turbocharger for the OM355 naturally... 

RFID systems are available in various applications for indoor and outdoor positioning. Location awareness in public environment and in stores and companies are widely in use. In indoor environment , multipath and fading changes signals specification, so it is difficult to detect the related parameters. In the other hand the necessity of fast and reliable system which support traffic and a large number of users are in demand. RFID which is based on radio frequency signals is developed for this aim.RFID system with asymmetrical link which support UWB and Narrowband signals is suggested for indoor positioning application. RFID passive tag in this system is redesigned in his thesis.... 

The objective of this investigation was obtaining sound Friction Stir Welded (FSWed) Commercially Purity Titanium using suitable Tool’s Materials (for Shoulder and Pin) in order to be able to work in high temperature (>1000 ˚C) with great mechanical properties and minimum wear during process. Consequently, different materials and designs for Tool, such as High Speed Steel tool, Tungsten based tool, Tungsten Carbide (WC-Co) based tool and diverse tool geometry and designs like simple design, threaded design, fixed pin and inserted pin (adjustable pin) was used. The results demonstrated that using simple cylindrical WC-Co for pin and Tungsten for shoulder resulted in joints with the best... 

Fog computing environment consists of several devices which distribute across an arbitrary topology. Each of these devices is capable of carrying out a designated computation simultaneously with other devices. One of the common ways of describing a computation is through the usage of workflows. Workflow is a flexible and formal way of modeling tasks and their requirements for execution. A workflow is essentially a DAG. Therefore, it can model the data dependency between tasks quite accurately. The complex structure of a workflow in conjunction with the homogenous nature of devices in a fog environment makes it difficult to find a resource management algorithm to minimize execution time, used... 

Commercially pure titanium (CP-Ti) is an important groups of titanium family and because of high strength, low density, high corrosion resistance and biocompatibility, this group of titanium is a suitable choice for application at chemical, petrochemical and medicine industry. Nowadays surgeons have a tendency toward use of CP-Ti instead of Ti-6Al-4V alloy. Moreover, because of body anatomy limitation, use of thick sheets result in high volume and damage soft tissue. Therefore, for sheet thickness reduction, study of the effects of metallurgical and geometrical parameter on fracture behavior of thin sheets is important. In this study, the fracture behavior of CP-Ti thin sheets investigated.... 

Power system operators are facing with imperative challenges to integrate high penetration of renewable power plants. The main challenge is required investment cost for accommodating the grid with uncertainties of renewable resources. In addition, intermittency and fluctuations of renewable resources are another challenges of system operators. Therefore, choosing a proper control procedure to respond the grid disturbances is a crucial task. However, the strategic behaviours of generation companies lead to a competition between them which affects the control performance. In this thesis, an integrated mechanism is proposed that consider both dynamic and strategic behaviours of generation... 

Resolvers, due to their robust structure, are widely used in automation systems. Among the types of resolvers, the accuracy of the Wound Rotor (WR) resolver in the occurrence of common mechanical errors is higher than other types of resolvers. therefore, in this thesis, an AFWRR is studied to improve the performance. Increasing the number of poles in WR resolvers is a good solution for increasing the accuracy of these electromagnetic position sensors. However, high-speed WR resolvers due to employing fractional slot windings suffer from rich sub-harmonics in the induced voltages. A common solution for suppressing the undesirable sub-harmonics is using multi-layer winding with appropriate... 

In recent years, due to environmental concerns together with rising costs of the fossil fuels, the wind energy usage in electricity generation of various countries has experienced a growing trend. Owing to inherent characteristics of wind turbines power generation, i.e. uncertainty in their output level as well as being undispatchable, the rapid growth of installed wind farms, however, has caused some new challenges in operation and planning studies of power systems. Among the major challenges in operation of high wind penetrated power systems, wind power curtailment has been emerged as a new problem in wind development. System operator may curtail wind farms output in order to meet system... 

Cancer can be defined as a stochastic phenomenon. Thus, the tumor growth can be defined as a stochastic process. A Cancer tumor can be analyzed by its geometric shape. Furthermore, computing fractal dimension of shapes is a useful technique to analyze chaosity and complexity of shapes. This approach can be used to compare results from laboratory with simulated results of a mathematical model. A stochastic model of tumor growth will be presented. And some geometrical properties will be analyzed through computer simulation of the model  

Solid oxide fuel cell (SOFC) is one of the promising candidates for clean energy production. Due to the high operating temperature of SOFC, a protective coating is commonly applied on the surface of interconnects to prevent oxidation. In this study, electrophoretic deposition was employed to prepare a manganese-cobalt spinel coating on the surface of ferritic stainless steel (AISISAE430) substrates. MnCo2O4 powder with an average particle size of 60 nm was utilized and the sintering behavior of the coatings at different temperatures was studied. Non-isothermal and isothermal sintering behavior of the powder compacts were examined by employing a sensitive dilatometer. Master sintering curve... 

Offshore platforms are one of the most important structures in oil-rich countries, so that their economic benefit makes it very expensive to stop their usage. Therefore, it is essential that their performance is not disrupted by earthquake or the tidal waves made by severe storms. In the conventional bracing systems, it is assumed that the braces buckle under compressive forces; but Buckling Restrained Brace (BRB) does not buckle under pressure. In this study performance of BRB in jacket platform, with a case study of Resalat platform, has been investigated under earthquake load and powerful wave. The modeling of jacket equipped with this brace has been done in Abaqus software, and results... 

The effects of combined task demands on the way muscles are recruited to balance external loads during posture and movement is of great importance in quantitative analysis of upper arm function. Pain and disability of shoulder joint is becoming more important as population spends more often interacting with computers in seated position and carrying repetitive tasks using upper extremities. Shoulder joint that is more dependent on the muscles for its normal function than other joints such as hip due to its small articular surface and large range motion has been used here to study its coordination during isometric exertions. Since, the numbers of tasks that could be performed are enormous. In... 

Offshore platforms are one of the most important structures in oil-rich countries, so that their economic benefit makes it very expensive to stop their usage. Therefore, it is essential that their performance is not disrupted by earthquake or the tidal waves made by severe storms. The new high performance semi-active bracing system, developed by Golafshani et al, is capable of removing the permanent drift of stories at the end of excitation and concentrating structural damage in braces. In the conventional bracing systems it is assumed that the braces buckle under little compressive forces; but in this new presented completely tensile-ribbed bracing system (RBS), buckling of compressive... 

The objective of this research is to model the wing structure of a flapping wing MAV and investigate structural dynamic behavior of its wing. in this research, to investigate and identify dynamic instabilities, modeling of the structure based on a nonlinear four-node plane element and aerodynamic modeling based on the strip theory in unsteady flow has been done, and by coupling these two models, the final model is formed. In the model of the wing structure, the displacement and changes angle inside the plane of the wing sections have been ignored and only outside the plane have been assumed for the degrees of freedom. In addition, the veins in the flapping wing have been omitted and the...