Sharif Digital Repository

The pressurized structure such as aircraft fuselage and pipeline (in the oil and water transportation) have a great importance in today’s world. There is a growing tendency in improving design factors, safety and maintenance of such valuable structures. Change of design’s philosophy during the time from infinite life to safe damage and safe life and after that damage tolerance, are a process leading to many changes in design and consequently the methods of inspection, evaluation and maintenance. In this way, using old methods like non-destructive test and evaluation (NDT/E) is encountered with different problems when damage is tiny and there is no coincidence in examination (inspection)... 

Usually the structures are designed based on the fixed-base assumption; however thisassumption is not always correct and the bed flexibility should be considered. This effectwhich is called soil-structure interaction, change the response of structure on both elasticand inelastic behavior. In the regulations for the design of structures on flexible base,generally soil-structure system is replaced with an equivalent fixed base structure; in theway that the design force of soil-structure system with reasonable accuracy can beestimated by equivalent fixed-base structure. In some regulations, dynamic characteristicsof equivalent structure have been determined on elastic state and the results have... 

In this thesis, turbine disk thermo elastic and creep stresses has been extracted and the turbine disk cross-section is optimized. Gas turbine disks are used at high temperature and high rotational speed. Due to high temperatures gradients, the mechanical properties vary along the radius of the disk. Most of the stresses in the gas turbine are exerted by centrifugal force and thermal strains. At first, thermo elastic and creep equations for these disks are derived, assuming plane stress and axisymmetry. The resulting differential equations are nonlinear and can not be solved using analytical solutions. Two methods are used to solve the equations which finally are verified employing the... 

The objective of this thesis is to develop a speech enhancement technique that can be applied for enhancement of speech degraded by additive background noise. The important aim of speech enhancement is to get better result after transmission at the receiver side. Additive noise such as White Gaussian Noise, Street Noise, Babble Noise, etc, is one of the speech enhancement problems degrading the intelligibility and quality of the signal. The important applications for speech enhancement are VOIP, Telephone services, mobile telephony, hands free voice control, communication between pilot cockpit, etc. Wiener filters are the mostly used techniques to reduce the uncorrelated additive noise with... 

Nowadays the growing demand for energy, and, on the other hand, the limited resources of fossil consuming energy in the world have caused the energy operation and consumption management to be taken into consideration much more than the past. Based on this background, improving the efficiency of feed conversion technologies in supplying the energy demanded by the consumers is the foremost and the most crucial solution to preventing energy loss. Another approach to reducing the losses through energy generation and transmission is the use of distributed energy generation systems in small scale. The advantages of applying this type of technology are the possibility of installing near the load... 

Low-frequency oscillation damping in power system is main determinants of the stability of the system. According to increasing of wind farms with high penetration levels in the power system, participation and control of wind farms for increase damping inter area oscillations seems important. In this study a damping controller suggested for Doubly Fed Induction Generator (DFIG). Using this controller and only available local signal as input controller and combination of both active and reactive power modulation, can greatly increase damping inter area oscillations and stability of uncertainty and different working points. Using linear analysis system, identified modes oscillating system and... 

Location observations from Global Positioning System (GPS) loggers are an important source of data for travel behavior researchers. Using GPS, requires a receiver, a digital map and a software that matches the user logged positions to the map. Identifying the location of the GPS data points on a coded map of the transportation network is not a trivial process. There is always an error in calculating the coordinates obtained from the GPS satellites, and also the available maps are not accurate enough. As a result, map-matching always carries some errors. Thus, different algorithms to do this mapping more precisely are presented. The output of the map-matching process is the identification of... 

Masonry buildings are one of the most vulnerable structures against earthquakes, and therefore their seismic response should be evaluated in order to mitigate casualties in the future. Although there are numerous experimental and analytical studies on these buildings, few have aimed on Confined Masonry (CM) buildings to simulate and predict their seismic performance. To estimate damage, assess vulnerability and choose the best retrofitting method, fragility curves can be utilized as a powerful tool. In this paper, the hysteretic behavior of two typical CM walls with and without opening is calibrated in both In-plane (IP) and Out-of-Plane (OOP) loading directions making use of OPENSEES... 

A geometric network is an undirected weighted graph whose vertices are defined as points in a geometric space, such as the real d-dimensional space. The weight of each edge of the network is equal to the Euclidean distance between the two endpoints of that edge.Geometric networks are used to model many real systems such as roads, communication networks, etc. When designing a network, one may consider different criteria. For lots of applications, existence of a short path between any two points of the network is important. The direct connection between any two points of a network is the ideal lution; however, this not possible in many applications because of its high cost. In order to... 

As long as the wind power penetration is low, overall dynamic behavior of a power system is determined by the interactions of system synchronous generators, but introduction of large amounts of new wind generation can affect the power system behavior. In this research, the impact of large wind farms on the small signal stability of power systems is studied. Because constant wind turbines are not very conventional in today’s wind industry and the dynamics of full converter wind turbines are isolated from power system, in this study only the doubly fed wind turbines are considered. In this order, a novel index is introduced to analyze the impact of doubly fed wind farms on the damping of... 

Regarding to the value and the modeling, damping has remarkable effect on the response of the systems. More over the structural damping the soil damping also exist in the soil-structure systems. Damping resources in soil include material damping and radiation damping. The high amount of radiation damping in some cases have been led to paying less attention to material damping in some studeis. Although in many cases this is not true and in systems with little radiation damping the material damping could be really important. Generally the role of soil damping depends on the properties of the structure. On the other hand in structures with multi-degree of freedom, soil existence affects the... 

In speech processing, reflections of sound wave in a bounded space are considered as speech reverberation. Although for musical instruments and their related recording devices these reflections are useful, however, some other applications face serious problems receiving them along with speech signal. Reverberation causes speech degradation and intelligibility as well as highly quality reduction. Dereverberation algorithms are essential for Automatic Speech Recognition (ASR), telecommunication and hearing aid devices, which are some of the mostly used applications. While dereverberation itself is a challenging problem, dereverberate a speech signal recorded only by one microphone (channel)... 

The Minimization of multi output Boolean functions is a fundamental and classic problem in logical circuits. For single output functions Karnough Map and Quine-McCluskey algorithms are the most common ways; however, for multi output functions they can be used to every output, but it does not necessary give the optimal solution. In this thesis we are going to compute simple expressions (expression in which we have just one type of operators) with minimum operations. We assume that we can use intermediate results in calculating other expressions to reduce repeated operations. In this thesis, first we compare the optimal solution of ‘and’ and ‘or’ operator with the ‘xor’ operator, and after... 

Optimized structure of the chlorophyll a and b molecules was obtained for LDA and GGA approximation by SIESTA package. Calculation illustrate that tails are curved in the optimized structure for both chlorophyll a and chlorophyll b molecules; in addition, Antennas, which are attached to the head of molecules, are located in optimized-spatial state. This optimized structure of chlorophyll a is similar to the calculated structure in ref [42]. Electrical dipole are calculated from ground state electron density of chlorophylls. Total electrical dipole of chlorophyll a for GGA and LDA approximation are 4.662 and 4.813 Debay, and these value for chlorophyll b are 1.435 and 1.302 Debay,... 

This thesis introduces and investigates a new kind of scheduling model, in which the total amount of computational resources to be allocated at each moment by the processor is constrained and upper bounded by a constant. The time for a task to be executed is also dependent on the computational resources, dedicated to it by the processor, assuming that the multiplication of the execution time by the dedicated computational resources is a constant for each job. We investigate various objective functions, such as minimizing the number of tardy jobs, minimizing maximum latency and etc, under varying constraints. The investigated objective functions are: a) Minimize number of tardy jobs b)... 

Nowadays, demands increment is one of the greatest concerns of energy systems operators. Consequently, enhancing the efficiency of consumption is an inevitable goal, which leads us to a concept named as energy hub (EH). In a simple definition, an EH is a multi-generation system where different energy carriers are converted and stored by various devices such as combined cooling, heating and power (CCHP), battery, and boiler to meet the load demands. In addition, with advent of smart grids (SG), demand side management (DSM) becomes one of the effective techniques with significant role in optimizing energy systems performance. DSM commonly refers to methods implemented by utility companies to... 

Nowadays financial and business jobs without new technologies and new methods to manage are not that much useful. Managers are searching for all new methods in different areas for improving their profit, quality of services or increasing number of their customers. Because of this, they would check some ways to prove their issues. But the point is that they should have a great view about their products, customers and generally their own shop. One of the perfect methods to present the form and relation between their favorite factors is complex network. With complex network they can have perfect sight about their system. Also, with some remarkable and noticeable ways they can categorize their... 

The main objective of this study is to identify the contribution of different damping mechanisms in equivalent damping of inelastic soil- structure systems which can be used to reach a better estimation of inelastic soil- structure systems response using some simplified methods. This mechanisms include the material damping of soil and structure, radiation damping of soil and also the structure’s nonlinear behavior. Despite the studies have been done, even in the fixed base systems, there is not an exact prediction for the contribution rate of inherent damping and energy absorption related to nonlinear behavior in equivalent damping of system. Considering the flexibility of soil under the... 

In process of making prosthetic limb, each of the prosthetic limbs must be costume fitted and built since each amputation of the patient is unique. The design and fabrication process of artificial limb consists of several different steps and begins with a precise measurement process that will be used to design the prosthetic limb. If possible, a prosthetist begins taking measurements before the patient's limb is even amputated, so that the fabrication process can get started. Today, much research which has been done in Augmented Reality and 3D scanning technologies shows that these technologies can help people with disabilities to have better experience in their life by using them in... 

One of the important tasks of operation manager is keeping system in safe and reliable situation. There are many tools that supply safety in the power system. One of them is operation reserve. Operation reserve is any type of capacity being used to support active power balance. In this thesis, an approach for optimal determining reserve capacity with considering dynamic constraint is presented. This thesis describes a method for setting the optimum value of reserve capacity based on the cost of its provision, the benefit derived from its availability and Frequency stability. The method that used is D-SCRM algorithm. However, as the size of power systems increases, the current centralized...