Sharif Digital Repository

The subject of this thesis is about a certain set of algorithms that try to indirectly solve problems. Instead of a programmer crafting an algorithm to solve a problem, these algorithms learn a solution themselves. These methods are usually studied in the Probably Accurately Correct (PAC) learning model. Although, PAC Learning is a generally accepted model, it falls short to describe certain aspects of learning algorithms. Many learning methods rely on convergence to minimize error, or maximize their fitness, yet the PAC model doesn’t explicitly provide any means to measure these behaviours. In this thesis, we first go through different models related to computational requirements of... 

Ultra-wideband (UWB) frequencies with low level of power spectral density, which is set by FCC standard, have long been utilized in many short range applications, namely sensor networks, indoor positioning and radar systems. As their name suggests, the ultra-wide bandwidth of this standard, covering frequencies from 3.1 to 10.6GHz, provides high data rate communications. Two of the most critical challenges toward UWB receiver design is narrow-band interference coexistence, including IEEE802.11a and jitter due to the very narrow width of the UWB pulse in time domain. General previously proposed solutions to receive these narrow pulses is based on correlation principle, which is very sensitive... 

In this thesis, first we will have a brief review on hash functions and related concepts.Then, we will descibe the hash function, Cubehash, which is one of the competitors in the competition held by NIST for selecting SHA-3 standard. Next, we will describe an attack based on linearization of differential paths in hash functions and apply this attack on Cubehash. At the end, we will discuss the results of this attack on Cubehash  

Chaotic Flow in transportation networks has been the subject of several studies. Evolutionary models have been employed to simulate traffic flows. This study takes advantage of an existing evolutionary model of traffic assignment to show that chaotic phenomena arise when the model’s driving force is speed or density, of traffic flow. It has been observed that drivers show higher sensitivity when the network is more loaded.

 

Today, building sectors account for 34% of total energy consumption in Iran. Increasing demand of the comfort level along with population growth necessitates much more attention about energy requirements in the country. Such phenomenon has already raised concerns about the heavy environmental impacts. The present research studies minimization of global warming potential effect for an educational building by developing life cycle optimization model. The Department of Engineering of Sharif University of Technology is selected as the case study and optimal solutions has been achieved for this building. Results state that implementing cogeneration and renewable energies can reduce20 -25% of the... 

In this thesis, we propose a new compressed-sensing-based algorithm for unmixing of hyperspectral data, and show that the reconstruction quality could be significantly improved. In addition, we illustrate that by utilizing this approach, we can achieve an approximate estimation of the Point Spread Function (PSF) of the hyperspectral images. In this way, we first assume that the PSF belongs to a specific family of functions, such as Gaussian, then, by sweeping the parameters of the assumed PSF, we obtain the abundance coefficient matrix of the reconstructed image. Now, by choosing the sparsest coefficient matrix as the best one, we estimate the corresponding PSF. Then, we further investigate... 

Semantic segmentation, a pivotal topic in computer vision, finds extensive applications across various domains. Leveraging deep networks to tackle this challenge necessitates a large dataset with pixel-level annotations, incurring significant time and cost for preparation. Weakly supervised semantic segmentation utilizes less expensive labels, such as image-level annotations, thereby circumventing the need for costly pixel-level annotations. Consequently, weakly supervised learning has garnered considerable attention. In recent years, vision transformers have achieved significant results compared to convolutional neural networks advancing the state of the art. However, employing vision... 

In recent decades, due to economic, political and environmental issues, tend to use of the CHP systems (combined heating and power) have increased. CHP systems not only increase energy efficiency, but also decrease fuel consumption and emission levels of systems. The use of CHP technology in the industry has a long history, but the use of these systems in the commercial and residential sector, is considered, recently. As to the residential buildings, both electricity and thermal energy demands fluctuate seasonally and hourly, so it is necessary to take account of the plant’s annual operational strategies for the variations of load demands. In this paper, a nonlinear programming model is... 

The purpose of this project is choosing optimal technologies of cooling and heating and production of usable hot water and also to use optimal thicknesses of heat isolating walls, roof, floor and heat isolating of hot water transfer piping that is done to minimize the expenses of technology, energy and maintenance of the technology. We did all of the above mentioned issues by depicting the energy balance. In this modeling, we first defined four scenarios. Then by using a linear mathematical model of integer, the optimum number of lamps selected in accordance with the standard lighting. In the next step, by using a nonlinear mathematical model, we defined the optimal thicknesses of insulators... 

Analysis of energy flow which effectively leads to reducing energy consumption in buildings is of major importance. The following research is the development of methodology and simulation of energy in the residential buildings and realization of the methods by means of FORTRAN software. In the process of modeling energy flow, in order to evaluate thermal comfort and calculate building’s thermal load, the dynamic and integrated interaction of these parameters must be appraised. The continuous and integrated study required that Mass and energy flow, for various component of building, and their interaction be examined. These factors could not be assessed using simple and reliable methods. In... 

In the building, can be used variaty of Heating, Ventilating and Air conditioning systems. Among the items that affect to select the hvac system can be pointed to building thermal demand and system energy consumpsion. simulation of this systems is one of the ways that can compare hvac systems in the building. according to Iran needs for preparation of software for optimization of energy carriers consumption in building proportional with existing matrials and equipment in the country, in this research has been tried methodology and modeling of hvac systems in the way developed that producted software is capable simply and practical for engineers be operational in a residential unit. In realy... 

This study is a modeling for “building’s energy consumption” as well as selecting an optimum composition of technologies to meet a building’s needs, with an approach of reducing energy and facility costs . In modeling the energy stream to evaluate heating comfort and to calculate building’s heating load, the interaction between these two phenomena is assumed to be en block. The unique and en block study requires surveying mass and energy streams from all particles of a building, which are not traceable in simple static methods. This study assumes a building with following requests: heating load, cooling load,air conditioning and heat water. An optimum selection of facilities and... 

Gas turbine is one of most widely used in power plants to generate electricity or mechanical power options in the industry , which is having its own advantages and disadvantages . if the turbine use simple , efficiency is generally below 33%. . After installing and employ , these turbines produce efficiency less than their nominal amount . The methods no change in structure exist that increase the efficiency or power of the turbine to acceptable level .In this thesis, gas turbine and to improvement performance methods has been studied . gas turbine with the methods are simulated to obtain the effect of each method in different environmental conditions . Economic sensitivity analysis...