Sharif Digital Repository

In this project, we developed a theory of monomial preorders, which differ from the classical notion of monomial orders in that they allow ties between monomials since for monomial preorders, the leading ideal is diffrent with monomial orders, our result can be used to study problems where monomial orders fail to give a solution. Some of our results are new even in the clssical case of monomial orders  

By studying of simulations, it can be seen that the linear point (LP), a point lies midway between the scales associated with the peak and the dip in the correlation function on BAO scales, is a useful window into cosmology and large scale structures rather than baryonic echo peak. Some fundamental features of the LP, been unaffected by redshift space distortions and gravitational non-linear effects, has made it important. I want to find evidences to stability of the LP by utilizing Standard Perturbation Theory through my thesis  

Considering the continuous growth of renewable energy sources in electric grids, the importance of utilizing simple, generic, and upgradable models for different network stability studies is increasing. In recent years, generic and standard wind turbine models for transient and short-term frequency and voltage stability studies have been developed. In this regard, researchers are still working on promotion of the generic models, especially to expand them for unbalanced transient studies, improve the transient response, and include inertia response. In this thesis, different methods for generic modeling of wind turbines are surveyed and the development procedure of WECC and IEC generic model... 

In this thesis we introduce the objective method for solving combinatorial probability problems and combinatorial optimization. For introducing this method, we consider its application in solving problems such as graphs maximal partial matching problem. Then we introduce mean-field model, which has a close relationship with this method. Finally we use this method to discuss perfect mathching with minimal cost in complete graphs, and using obtaind theorems and concepts from solving this problem, like involution invariance and standard construction, we find an answer for random assigment problem, which is one of the most practical problems in the class of optimization problems  

With the advent of the globalization paradigm, the industrial interactions among manufacturing companies have become easier, and the possibility of sharing of the resources among them has been introduced. This issue, coupled with the increasing diversity of customer needs, has led to a change in business models of manufacturing industries and because of that, in the field of globalized manufacturing, a new paradigm called cloud manufacturing has been proposed in which service-orientation is one of the main features. Despite of the extensive studies on cloud manufacturing, the lack of a framework that, based on the service-orientation, determines the improving of manufacturing processes to... 

TETRA (TErrestrial Trunked RAdio) is one of the mobile telecommunication standards which has improved in several aspects (voice, data, video, coverage, etc.), especially the security section during the last two decades. Although communication could be quite secure in TETRA when the encryption is used, however, attackers create new ways to bypass the encryption without the knowledge of the legitimate user. Security is performed in different levels and forms to create reliable operation and to protect information through the transmission path from interception and tampering. Since most of the TETRA users require the highest possible level of security, in this thesis we introduce a new... 

Formulating of general relativity and the assumption that gravity is only effective interaction in large-scale universe, has been a beginning for surveying the whole universe , its start and its end as a physical phenomenon. According to the Friedmann's answer to the Einstein's equation , Hubble observations and CMB radiation observations , the Big Bang model was accepted as the standard model of cosmology.
According to this model , the universe which is assumed homogeneous and isotropic , starts from a singularity (Bang) and is currently expanding. In 1970s after some tentative researches like observation of homogeneity and isotropy of CMB and visionary researches some problems like... 

Cosmic Inflation, invented by Alan Guth in 1980’s, solves the shortcomings of the Standard Cosmology such as the flatness, the horizon and the monopoles problems and provides the seeds of large scale structure formation. The quantum fluctuations which are produced during inflationary epoch are redshifted and transferred from Microscopic scales to Macroscopic universe. We can observe this macroscopic fluctuations both on the CMB surface and on large scale structures. Data from WMAP and Planck missions(CMB space Telescopes) suitably confirms the general predictions of single field inflationary scenarios but still people search for finding primordial gravitational waves from the B-Mode signal... 

Cerebral palsy is a disorder and a condition that occurs before, during or after birth. According to reports, in developing countries, out of every 1,000 births, 3.5 cases develop cerebral palsy. One of the consequences of cerebral palsy is unusual walking due to nerve disorders, including severe spasm of the lower muscles of the trunk. Drugs, therapies, and orthopedic surgeries are used to help patients with cerebral palsy. Improper orthopedic surgeries have severe effects on the patient's function. You can partially solve these problems by using the gateway category. The common patterns of cerebral palsy gait help decide the treatment method. In recent years, the use of gait analysis has... 

One of the most important parameters of a smartphone is the ability to operate in a long time with a rechargeable battery. As a result, the design of radio frequency circuits which are used in these cell phones is a consistent challenge for designers. Bluetooth Low-Energy standard (BLE) which is the fourth edition of Bluetooth standard is recently introduced with the aim of transporting low volume data with minimum power consumption. The most important challenge of the design of an RF receiver in the BLE standard is the power consumption. In a typical receiver, the oscillator and the mixer are the most power hungry blocks. Therefore, decreasing the power consumption of these two blocks is... 

Multimedia applications which exploit the network resources are best provided in broadband networks. Additionally, broadband wireless access systems enable broadband access in places where the wired solutions are not applicable. The IEEE 802.16 standard is designed to provide broadband wireless access and addresses the PHY and MAC layers of wireless metropolitan area networks. This standard has been designed to support quality of service for different applications, and due to their various requirements has considered four classes of service for connections. However, quality of service support mechanisms (such as admission control and packet scheduling), are out of the scope of the standard.... 

Nowadays risk is one the major concepts of personal and social work aspect. For researchers have been working to propose solutions for risk management in different level of projects. Project risk management has been known to be one of the major research areas conjugated with knowledge management solutions. However no proper solution for fulfilling a proper structure of risk management has been found. The main aim of this thesis is to find a well defined structure to enable the risk management concepts in project management. But the definition of such system is known to be so complicated due to vast area of related requirements which can be found for risk management. Moreover this solution... 

Variations in supply and demand of transportation, as well as those in the related environment, would cause daily variations in user travel time of transportation networks. This phenomenon particularly happen in morning travel time peaks, and make estimation of travel time highly unreliable. Morning peak passengers, whose timely presence at the destinations are highly important to them, prefer to choose paths that have minimum travel time and maximum reliability. Thus, the look at travel time pessimistically, and based on their experience, they put a margin of reliability to reach at timely at their destinations.
This study analysis such reliability margins based on the standard... 

Data collected from street networks show that travel time in urban street networks is a stochastic variable, whose range of variation increases with the congestion level. Work and school trips comprise the major part of morning peak volumes, whose common characteristic is that they need to be made on time. For this reason, these travelers are pessimistic in their route choice, and try to choose routes which are more reliable. Travel time standard deviation is one of the common measures for estimating travel time reliability that is related to properties of day-to-day travel time distribution on a particular route. Based on the empirical data collected from Tehran street network, this paper... 

The Reliability of substation structures with consideration of earthquake uncertainties is one of the most important subjects in structural analysis in recent years. In this project we first introduce IEEE-693-2005, which is the most effective and comprehensive seismic design code for electronic substations. Also in second chapter the rudimentary aspects of Reliability Theory and methods for evaluating the reliability of substation structures is introduced. Then with modeling the most common and most important electronic substation devices in Iran, with consideration of all seismic parameters and their uncertainties, the reliability of these structures evaluated. In this project for... 

In spite of succesfull achievements of standard quantum mechanics in describing variety of physical phenomenons, this theory has some conceptual problems in some areas. One of the important problems is the behavior of macroscopic objects and their interaction with microscopic systems, which is called “measurement problem”. Actually because the standard quantum mechanic is linear, it anticipates the occurrence of superposition of macroscopic states which is in contrast with our understanding of macroscopic objects. The standard theory answers this problem by using the wave function reduction principle.
There has been various proposals about the mechanism of wave function reduction,... 

Total knee replacement surgery is the most common joint replacement in the world. Considering the increasing rate of this procedure and costs and difficulties of the repeated operation, many efforts have been made to improve the performance and lifetime of implants. The Polyethylene component of the implant is the most prone component to fail due to wear. To evaluate new knee prosthesis designs, it is necessary to have a wear test simulator. Objective of this project is to detail design a knee prosthesis wear simulator according to ISO 14243 in order to investigate the performance of prosthesises in long term and under in-vivo conditions. During this project, studies have been made to get... 

The process of aging is accompanied by problems that can affect the daily activities of an elderly. Recent studies have shown that the use of virtual reality technology provides a variety of diagnostic methods and clinical systems to prevent and delay cognitive aging to ensure the normal life of the elderly. In this project, efforts have been made to design some virtual reality-based games focusing on memory and recall in the form of three scenarios of finding address, finding car, and virtual-reality based maze game for the elderly to prevent cognitive decline and developing the dementia so that the difficulty of the game level ahead of each elderly can be adjusted according to his or her... 

Despite the astonishing successes of quantum mechanics, due to some fundamental problems such as the measurement problem and quantum arrival time problem, the predictions of the theory are in some cases not quite clear and unique. Especially, there are various predictions for the joint spatiotemporal distribution of particle detection events on a screen, which are derived from different formulations and interpretations of the quantum theory. Although the differences are typically small, we show that these predictions can be experimentally distinguished by a proposed unconventional double-slit configuration, which is realizable using present-day single-atom interferometry. Furthermore, we... 

Policy evaluation, is a crucial stage of any policy-making process. In many cases, unfortunately, this crucial stage, has been largely neglected. The marriage loan payment policy is designed and implemented to tackle the decrease in the marriage rate in Iran. However, the effectiveness of this policy has not been evaluated so far. In this research, we focus on evaluating the effect of the marriage loan payment policy on the marriage rate. Annual data at the provincial level between 2013 and 2021 is used. Dynamic panel data model and System GMM estimation method are employed to assess the effect of this policy on the marriage rate. The results show a positive and significant effect of the...