Sharif Digital Repository

In this thesis, we provide a comprehensive overview of the efforts made towards achieving the goals of Hilbert’s program, and evaluate how successful They are. We begin by discussing Gödel’s incompleteness theorems, and then as a first attempt we present a brief presentation of Gentzen’s consistency theorem. Subsequently, various research fields that branched out from these initial efforts are explored, encompassing the application of the Omega-Rule, reverse mathematics, and self-verifying systems. Furthermore, we present the concept of “Almost Finitistic Consistency” as an alternative approach within Hilbert’s program. In conclusion, a thorough assessment of the success of Hilbert’s program... 

Question answering systems are systems which get a question in natural language as input and present an explicit, appropriate answer to the question. One of the major components of automatic question answering systems is question processing component in which the input question is analyzed. The main goal of question processing phase is to determine the answer type through question classification. Rule-based, machine learning-based and hybrid approaches have been used in order to develop question classifiers among which machine learning-based ones have outperformed the others. This study’s main goal is to develop a question classifier for Persian open domain question answering systems.... 

Digital video is one of the biggest part of digital data. The first step of digital video analytics is shot boundary detection. We used overlapped partitioning beside color histogram in uncompressed data and macroblock type prediction in compressed data as feature and supervised classifiers for decision making. Tests on TRECVID 2006 shows 8.9% improvement of F-measure in uncompressed video and 5.3% in h.264 bitstream. Supplementary test is done on IRIB dataset which shows 5.7% improvement of F-measure in uncompressed and 3.2% in H.264. H.264 based algorithm is almost 7 times faster in comparison to the algorithm that includes decoding  

Due to the increasing spread of metal industries and the need for raw material as feed for electric furnaces in order to produce cast iron and steel, as well as scrap deficiency and rising prices, the use of sponge iron as a substitute for scrap was considered in this project Therefore, in order to achieve the chemical analysis of the sorel ingot that is special for spherical graphite cast iron production with low manganese and chromium content, the direct reduction process was carried out using tunnel kiln method on low-manganese iron ore concentrate.After the investigation on direct reduction parameters including the saggers and coal grading,the produced sponge iron has melted in... 

Fuel system is one of the most important parts of pulse detonation engine which has the responsibility of fuel, oxidizer and also purge gas in the different operational frequencies of engine. Although pulse detonation engines are sort of air breathing engines and purge gas and oxidizer one in the same unit in their structure, due to existence idea in the pulse detonation rocket engines coverage of functional condition, fuel, oxidizer and purge gas, will study it in three different structures.
In this study purpose is improvement of the pulse detonation engine of Sharif University which will provide as the possibility of safe functional condition and high operational frequency in... 

Auction is one of the most important and oldest institutions in economics, enabling resource allocation and trade of goods in the economy. Investigating the effects of changes in reservation price in auctions is an important question in auction theory research. In this study, focusing on a policy implemented by Yektanet, which involved altering the reservation price in auctions for advertising slots, we assessed its impact on advertiser costs. The implemented policy led to the activation of two distinct mechanisms, resulting in conflicting effects on the company's revenue. The first mechanism involved an increase in bid and intensified competition for ad placements on average, while the... 

Epistemic logic gets its start with the recognition of the systematic properties of epistemic concepts. These properties make epistemic concepts amenable for formal study, and become our tools to present logical models for them.“Certainty” is one of these epistemic concepts for which no comprehensive logical model has been presented so far.
Among the logical models that have been presented for “Certainty”, there are two main models which are more comprehensive than the others and all the other models may be extendable to one of them. In this thesis, these two main logical models that have been proposed for the concept of certainty are introduced and described from a philosophical... 

There are a lot of methods for the settlement of the reserve power market which can ultimately lead to a pattern of consumption and generation for each of the participants of the power market. After this step, however, justified and logical methods should be utilized for paying the reserving costs to the participants as in a long-term it can optimize the economic conditions of the market which can result in getting more realistic bidding from the participants. The current methods used for paying the reserving costs are mostly locational marginal prices and pay-as bid approach. By the same token, for receiving the reserving costs from the customers, some consider the desired reliability level... 

Recent advances in storage and processing, have provided the ability of automatic gathering of information which in turn leads to fast and contineous flow of data. The data which are produced and stored in this way, are named data streams. data streams have many applications such as processing financial transactions, the recorded data of various sensors or the collected data by web sevices. Data streams are produced with high speed, large size and much dynamism and have some unique properties which make them applicable in precise modeling of many real data mining applications. The main challenge of data streams is the occurrence of concept drift which can be in four types: sudden, gradual,... 

This thesis reviews briefly historical backgrounds and contexts of Darwin's theory and summarizes and describes his arguments in the Origin, and studies philosophical issues around Darwinism. This thesis includes four chapters: chapter one reviews historical line from Greek thinkers to ninteenth century scientists; chapter two summarizes ideas and arguments in the Origin; chapter three discusses some philosophical issues briefly; and chapter four is devoted to some conclusion  

This research is trying to investigate the control algorithms of unknown control direction systems. Since Nussbaum function is the most common method which in used for these systems this research focus on this algorithm to overcome control the effect of unknown control direction. This research study the performance of different control algorithms in controlling such systems followed by analysis of two control modes of continuous and discrete using Nussbam Function. Additionally, in continuous mode, the performance of two methods of backstepping and liding mode has been compared on the given system in variety of situation. Results demonstrate that backstepping method shows better performance... 

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... 

Punctuation marks in every language, constitute an important part of a text. Not inserting these punctuations in text, makes the text ambiguous. The output text of automatic speech recognition (ASR) system, is typically a raw sequence of words, containing no punctuation marks. This makes the text difficult or even impossible to make sense of for humans, as well as for any further text processing tasks. The goal of this thesis is to perform automatic punctuation insertion in Persian texts lacking punctuation marks. To the best of our knowledge, this is the first work done in this context for the Persian language. For this purpose, firstly, we assembled a state-of-the-art corpus to train and... 

In the past, opinion polls have generally been conducted using statistical techniques and the comments of those samples, which, in addition to its various challenges, require much power and cost per poll. Today, due to the high penetration rate of social networks in society, a very large fraction of people discuss such issues in terms of their opinions and preferences in these networks, and hence, these networks can be a valuable source of information to get the opinions of people in a short time, and by lower cost.The purpose of this thesis is to enhancing the results of the surveys which have already performed using various methods of text processing in social networks by using the graph... 

Multi-agent systems have been attracting much attention in various fields due to their enormous potential applications, such as network control, distributed control, surveillance, etc. One of the most important issues in multi-agent systems is consensus, which refers to the problem that an agreement state is reached as a result of local communication.In order to reducing the necessary computations and the number of communications between agents, the event-triggered control was introduced and this excellent control scheme has received considerable attention of researchers.Time delay in multi-agent systems cannot be avoided duo to the signal processing and propagation. Hence, it is natural... 

Natural disasters such as storms, earthquakes, floods, etc. are among the factors that can damage the elements of the power grid and cause them to leave the grid. The result of these outages will be a widespread power outage, which will create many economic and social problems. Therefore, in recent years, the concept of resiliencey has been introduced in power system studies, which examines the extensive outputs in the network as a result of natural disasters.One way to improve the power system resiliency is to strengthen the network by upgrading existing equipment, installing new equipment, and modifying the operation of the network. Among these, the installation of distributed generation... 

Linear controllers have become popular in the industry because they have a simple structure and are easily implemented. But, they have fundamental limitations like waterbed effect and Bode’s phase gain relation. To overcome these limitations, other types of controllers have to be used like nonlinear controllers and reset ones. The hybrid integrator-gain system (HIGS) is one of these systems that has been able to overcome these limitations very well.Partial resetting and achieving variable phase in output are essential features in reset systems that have not been developed in HIGS. Here we are interested in generalizing HIGS to accomplish these features.Calculating higher-order harmonics is... 

Microgrids will be key components of future smart grids that integrate distributed generation energy with local loads and units for greater efficiency. However, the uncertainty and intermittent nature of renewable energy products prevent the reliable operation of the micro-grids. On the other hand, the introduction of electric vehicles into the transportation industry can be both a challenge and an opportunity for the power grid. Using electric vehicle batteries as an energy storage system is a new work in the smart grid environment. Using an electric vehicle battery as a storage system makes it possible to create a grid with a lower operating cost because of the development of renewable... 

With the rapid increase in the number of vehicles and the limitations on the extension of transportation network infrastructure, the need for utilizing proper methods to reduce traffic congestion has become increasingly important. One way to reduce traffic congestion is to control the signal splitting of traffic lights. Model predictive control (MPC) has been utilized so far by using different models of traffic flow dynamics in this field. Due to the high computational effort of MPC at each step time, the real-time implementation for large-scale networks has become a big challenge. Store-And-forward (SAF) is one of the traffic flow models that, due to its simplicity, makes it possible to... 

Positron emission tomography (PET) imaging is a cross-sectional imaging method in nuclear medicine. In recent years, there have been increasing interest in this method.PET imaging is very sensitive and the presence of noise in the results decreases the the image quality and precision of detection. Thus it is critical to to investigate noise in PET systems with noisy images, since it could decrease the system’s ability to detect tumors. The common method to decrease noise in nuclear medicine images is the Fourier transform (FT). The method has many applications in image processing and analysis. However, in the FT method, information regarding time and position are lost in the frequency...