Sharif Digital Repository

Multicore platforms prepare a great opportunity to implement fault-tolerance techniques. Task replication is a well-established technique to obtain high reliability against transient faults. However, replicated executions can increase power consumption more than Thermal Design Power (TDP) constraint. TDP is considered as the highest sustainable power that a chip can dissipate before being forced to exploit a performance throttling mechanism, e.g. Dynamic Thermal Management (DTM). If the chip violates its TDP constraint, it automatically restarts or significantly reduces its performance to prevent a permanent damage. Therefore, due to the unwanted system restarts, DTM techniques may not be... 

The subject of this study is design of a linear quadratic Gaussian controller based on identification of dynamic behavior of unmanned model helicopter “Raptor” in its hover flight. To achieve this end, first, the helicopter linear transfer functions are identified with frequency response method by applying specific inputs to the model of Raptor in the X-Plane software and receiving system outputs via Simulink. Next, using the identified dynamic model of the helicopter, an optimum linear controller is designed for hover flight. As an optimum linear controller needs all the state variables, a Kalman filter is utilized to estimate them, using outputs of various sonsors such as GPS and gyro.... 

Modern sensors consist of arrays of detectors specially arranged to enhance precision, capabilities, and field of view (FOV). Sensor arrays can have multiple functionalities such as the simultaneous detection of position and motion. We use a linear sensor model and develop an optimization method to design an array of photodiodes. Our objective function minimizes bias and variance estimations. We introduce a maximum likelihood technique to approximate and determine the bias caused by measurement errors, and verify our theory by statistically complete simulations. We apply our theory to design an optimal sun sensor. The sensor has a predefined conical FOV, and its accuracy is controlled by a... 

Condensation from a gaseous phase is a common method for the fabrication of metallic nanoparticles. Electromagnetic induction furnaces are the most common equipment used for this method. Since the sample doesn’t touch any foreign object, this method is one of very few ways to synthesize ultrapure nanoparticles. However, a major setback of this method is its low production rate.One of the only workarounds to this issue is to increase the melt’s surface area so as to present a larger surface for evaporation. In the common setup for this furnace the molten sample takes on a spherical shape which unfortunately holds the lowest surface to volume ration of any shape. The endeavor in this study has... 

Supply chains are socio-technical engineering systems which now days perform in more uncertain operational environment than before. These systems have been vulnerable because of increasing the number of natural disasters, competitiveness and changing the demand. So these systems in order to be survived in such high uncertain environment need to enhance some capabilities in their structure. In this research by considering an assumed auto supply chain, we try to develop an approach to cover uncertainties in operational environment of this system. At the next step, we use design structure matrix modeling to model the interactions between system elements before and after scenario occurring.... 

In recent years in assembly line balancing area many researchers have focused on identifying and modeling real world situations in assembly lines in order to obtain more suitable model. As a result many generalized models have been developed in assembly line balancing area. However, designing efficient algorithms to solve these generalized problems has just begun. In this study it is aimed to design efficient algorithms to solve one of these generalized problems. Specificcally two hybrid genetic algorithms (GA) are proposed to solve assembly line balancing problem with sequence dependent setup times. Scheduling of tasks in the stations has been less considered in the literature of assembly... 

Software modeling is one of the most important activities in the Software Engineering domain. Models provide an abstract view of the system, thereby facilitating their understandability and resolving the complexities and problems involved. Indeed, models can be considered as a roadmap for achieving the goal of producing software-intensive systems. The aim of real-world modeling is to identify real-world entities, their interactions, and the constituent activities. Real-World Models are tangible to all stakeholders and provide them with an overall view of the Problem Domain. Therefore, many software development methodologies are based on modeling the real world. In some of these... 

Due to the growth of energy consumption the use of new technologies and efficient energy conversion is necessary. An example of efficient energy conversion technology is CCHP (Combined Cooling, Heating and Power). The aim of the present research work is to develop a model that could be applied for optimal design of a hybrid CCHP system which would be Solar Combined Cooling, Heating and Power (SCCHP). In order to do so,microturbine power system, cooling and heating equipment’s such as absorption system and heat exchanger and also solar collector have been considered as an integral part of the system. The objective of the application of the model has been to identify proper sizing of all... 

Using superconducting synchronous machine leads to many advantages such as increasing overall efficiency, decreasing mass and valume of peropulsion system, eliminating some restrictions in hydrodynamic design , etc. The goal of this thesis is design of 200 kW, with 250 rpm superconducting synchronous motor for small ship propulsion drive application. The low speed motor can be directly coupled to the propeller whitch eliminates bulky and inefficient gearbox. After comparison of different structures of superconducting synchronous machines, finally rotating superconducting field with stationary copper armature winding is selected as the most approporiate structure for our application.
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Low power and high speed analog-to-digital converters (ADCs) are the key elements of communication and computing systems. There are several ADC structures such as delta-sigma, flash, pipeline, and successive approximation register (SAR) for different applications, albeit SAR ADCs are natural candidates of onchip designs for their low power and scalability benefits. Nowadays, SAR ADCs are widely being used in low-power moderate-resolution applications which need several tens of MS/s to low GS/s sampling rates. By virtue of the technology scaling power consumption of digital parts of a SAR ADC is reduced significantly. As a result, in a SAR ADC the power consumption of the digital-to-analog... 

One of the most prominent issues in road safety is to observe reaction time and sight distance in geometric design. Various sight distances are available is Iran's specifications on "Geometric Design of Roadways" taken from the AASHTO standard from which stopping sight distance, decision sight distance and their corresponding car driver reaction times are noteworthy. This research puts effort in obtaining these values for bus drivers in Iran. To achieve this, a test designed using bus driving simulator apparatus, developed in K.N.Toosi University of Technology, was conducted on a number of bus drivers. Obtained results of driver behavior were then analyzed and compared to corresponding... 

This thesis investigates the performance of concentrically braced frames through numerical simulation approaches. During a moderate to severe earthquake, the bracing members and their connections are expected to undergo significant inelastic deformations into the post-buckling range. Recently, provisions for special concentrically braced frames (SCBFs) were developed to exhibit stable and ductile behavior in the event of a major earthquake. Special Concentrically Braced Frames (SCBFs) are distinguished from Ordinary Braced Frames in that they possess improved post-buckling capacity. Performance based evaluation of SCBF system as well as ordinary concentrically braced frame (OCBF) system... 

Although the moment frame can show deformable behavior against seismic loads, but its flexibility and low stiffness, especially in tall structures, cause the governance criterion to be designed. The use of eccentrically braced frames was able to solve the displacement problem to some extent, because it has the characteristics of both flexural frame systems and conccentric bracing. Different methods have been proposed to eliminate residual displacements in this type of system, one of which is the use of post tensioned cables. The aim of this study was to investigate the seismic behavior of a steel structure with a eccentrically braced frame system with post tension cable.The cables are anchor... 

From the cache of the personal computers to the main memory unit of SOCs, medical and wearable chips, Static Random Access Memory (SRAM) is widely utilizes. Preferable performance for SRAM varies with regard to the operating field. For instance, high speed access and performance is emphasized in the design of the cache for PCs. In contrast, power consumption and the area of the memory are the key design considerations for SOCs. Hence, the field in which SRAM is used, should be thoroughly studied. SOCs and medical chips suffer limitations in design due to using batteries as the source of energy and SRAMs consume a significant part of total power and occupy a large area on these chips. One of... 

Plants, distribution centers, and other facilities generally function for years or decades, during which time the environment in which they operate may change substantially. Costs, demands, travel times, and other inputs to classical facility location models may be highly uncertain. So when making decisions of location considering the factors that may change is beneficial. In this thesis a version of covering location model under uncertainty in a congested system is proposed. The aim is to locate m facilities to maximize the captured customer utility, having in mind that there may be up to q facilities established in future; the only information at hand about the number of the new facilities... 

Additive manufacturing (AM), also known as Rapid prototyping or D printing, is a new technology for the manufacturing of the physical parts through an additive manner. In the AM process, the orientation pattern of the part is one of the most important factors that significantly affects the product properties such as the build time, the surface roughness, the mechanical strength, the wrinkling, and the amount of support material. The build time and the surface roughness are the more imperative criteria than others that can be considered to find the optimum orientation of parts. In this research, Two method is used to optimize part build orientation (PBO). In the first method a new combined... 

Hydrazine is considered as one of the most dangerouswaste materials from the environmental point of view. It can lead to both air and soil pollutions. Unfortunately,Hydrazine fuel is largly used in aerospace industry. Therefor, the aerospace industries are indirectly engaged with such pollutions.As a remedy incineration can be considered a very effective solution to destroy hydrazine fuel. In this thesis, we are faced with the conceptual design of an incinerator, which is going to be used for hydrazine incinerations.In this regard we are expected to consider all restrictions,which are required to be considered in a reed incinerator design and application. Therefore, we need to determine... 

Network design problem has been, and is, an important problem in transportation. Network design based on different objectives affects network's performance in different dimensions, so it is crucial to define a good objective for the network design problem that improves the network's performance in more than one aspect. The purpose of this study is to obtain the differences between the two network design problems, one based on resiliency, and the other based on consumer surplus.Network design problem based on consumer surplus minimizes the total travel time for the users in the network. Network design problem based on resiliency is defined as: (1) before the incident, (2) after the incident... 

A tsunami is a series of tides most commonly caused by the deformation of the sea floor during a submarine earthquake. They are extremely long waves with the distance between successive peaks or troughs on the order of 10’s to 100’s of miles. They are also generated by landslides, volcanic eruptions or more rarely by asteroid impact. These causes change in location on the surface of the water which in turn creates numerous waves that spread out from the zone of turbulence. Few current design codes for coastal structures include tsunami. Even those that do, the bases for taking the hydrodynamic loads into the design are often grossly simplified and may be overly conservation and/or... 

In recent decades, electricity generation using renewable energy sources especially wind has gained considerable attention worldwide. Various generating systems have been proposed for wind turbines to convert wind mechanical power into electrical power. Up to 70% of the installed wind turbines incorporate Doubly-Fed Induction Generator (DFIG) and a fractionally rated power converter. Other schemes still have technological and economic penalties such as high cost of active materials, complexity of machine manufacturing and control systems and large and expensive converter, which limit their spread in wind power plants. Among these, Brushless Doubly-Fed Induction Generator (BDFIG) has...