Sharif Digital Repository

Todays we do not have the traditional hardware speed acceleration anymore. We have reached to the highest possible speed of single core processors. Thus, in order to run an algorithm faster we need either to improve the algorithm and make it more efficient, or to use a more powerful hardware to run it. For algorithms which we have reached to their lower bounds, we can not improve their efficiency. Furthermore, we can not have any faster traditional processor, so the only way is to use the power of parallel computation. With the advent of multicore processors the software industry has faced a new challenge, to adapt the softwares to use the power of these new processors. There are a lot of... 

The amount of ever-growing generated data increases the need for automatic methods in text processing. As a solution, sentence compression and text summarization are considered as methods of managing and dealing with this huge amount of data. Additionally, Sentence compression is also useful in different text processing systems such as text summarization, news condensation, information extraction and question-answering systems. A sentence compression system takes a long sentence as input and returns a shorter form of the sentence in a way that its important information and grammaticality is preserved. In this thesis, we devise a rule-based extractive sentence compression method. This... 

Observed performance of nonstructural components and building contents during recent earthquakes demonstrated their significance to control economic seismic losses and downtime. Since a large portion of nonstructural equipments installed in buildings are acceleration sensitive devices, reasonable estimation of the acceleration they undergo during an earthquake has an important role in rational design of secondary systems and subsequently in reducing the earthquake damages. Although a comprehensive amount of research studies have been conducted to date to approximate the floor acceleration demands of a multistory building subjected to the earthquake ground motion, in most work, the soil... 

In recent years, increasing attention has been paid to the fractional calculus as a powerful tool for more precise modeling of real world phenomena. Also, it has been shown that using this tool in designing control systems results in controllers that are more efficient in comparison with their traditional integer order counterparts. In spite of the advantages of fractional order models, the difficulties in the implementation of this type of models are still the main concern of the control system community. Clearly, as a model becomes simpler, its implementation becomes more convenient. Therefore, one way to rectify the implementation problems is to model the intended system as simple as... 

Interactions among proteins and resulted networks of such interactions have a central role in biology. Aligning these networks leads effective information such as finding conserved complexes and evolutionary relationships. The inofrmation provided by global alignment of these networks is more meaningful in comparison to local alignment. In the problem of global alignment, time complexity is one of the most important challenges. Today, multi-core processors are used to solve many time-consuming bioinformatics problems. In this thesis, after reviewing pervious approaches on global alignment of biological networks, we present two novel algorithm for this problem. The first one is designed for... 

In this thesis, the problem of failure-tolerant control of the satellite in coupled orbital and rotational motion is investigated. All of the actuators of the satellite are thrusters and only the failure of the actuators is considered. At first, the equations of coupled relative translational-rotational motion of the satellite are derived. Then, the required specifications of the approapriate control method for the problem is explored with the conclution that the controller must be able to predict the behavior or planning the future trajectory of the satellite. In the next step, model predictive control, which has the required specifications, is used to control the coupled... 

After school tutoring education is a concept that varies widely between countries. Evidence suggests that one of the factors explaining this difference is the existence of competitive tests. There is also evidence for Iran that, because of the existence of competitive test of the national entrance exam, a large percentage of Iranian families use after school tutoring to their children get a successful result in this exam. But the question is how much after school tutoring is effective? The answer to this question is important because if after school tutoring is effective, low-income families are expected to be unable to provide such training, and the national entrance exam will prevent... 

Continuous casting is one of the ingot production methods in which the product has uniform chemical structure, low defects and high production rates. These days, carbon steel and nonferrous alloys are mainly produced by this special method. The design of continuous casting process includes a lot of difficulties due to its technological complexity. One of the most important aspects of this process is the heat transfer during solidification. In the present study, a new mathematical model and its corresponding numerical solution method have been introduced to establish the condition of directional solidification along the major ingot’s axis. The controlling parameters used in the model are... 

Recent research suggests that the electrochemical deposition of cobalt-based binary alloys, such as cobalt-tungsten and cobalt-iron, can lead to the formation of amorphous structures in the coatings. Theoretical studies suggest that these structures are equivalent to structures created by the melt cooling of the alloy at speeds of about 〖10〗^10 Kelvin per second. The formation of a glass phase can significantly increase the abrasion resistance and corrosion resistance of these coatings. Empirical studies show that the ability of the glass to become glassy, or more precisely, the transition from crystalline to amorphous, is largely a function of the chemical composition. Simulation of... 

Although the anisotropy of the solid-liquid interfacial free energy for most metal alloys is small, this anisotropy plays a significant role in the growth rate, morphology, and preferred crystallographic directions in dendritic growth. In recent research, the binary nickel-niobium alloy has been suggested as a suitable substitute for studying the solidification behavior of the superalloy Inconel 718. In this study, using molecular dynamics simulation with the LAMMPS software, pure nickel and Ni-%1Nb, Ni-%5Nb, and Ni-%10Nb alloys were examined (composition is based on atomic percent). After equilibrating the liquid and solid phases at the melting temperature, the interfacial phase was studied... 

The price elasticity of gasoline demand is a key parameter in evaluation of various policy options. However, most of the literature uses aggregate data to identify this elasticity. Temporal and spatial aggregation make elasticity estimates unreliable. We employ a unique dataset of all gasoline transactions in Iran during a four-month period around an unexpected exogenous price change to identify price elasticity. After controlling for date and individual fixed effects we estimate a robust significant price elasticity of -0.127. Aggregation of the same data by week, month, and city yields an estimate of -0.3 indicating a significant bias in earlier studies. We also identify a significant... 

In recent decades, local, regional and national research programs have discovered stormwater runoff as the principal cause of water pollution in most urban areas. To solve urban stormwater runoff problems, we should use revisory measures. This is possible by using Best Management Practices (BMPs). BMPs are innovative technologies to reduce the movement of pollutants from land into surface or groundwaters, in order to protect water quality within natural and economic limitations.Three types of BMPs are discussed in this study; swale, bioretention systems and pond. They have different installation requirements, costs and pollutant removal efficiency. The main objective of this research is to... 

Soldering is one of the important methods in joining techniques which has wide applications in industries such as microelectronic. Today, the physical and mechanical properties of solder joints is very important because the dimensions of electronic devices are decreasing that cause to increasing of their current density. One of the important problems of high current density in solder joints is the microstructures of solders in microelectronic components, change over time that is weakened the properties of the solder alloy. This study presents a quantitative model , which is capable to simulation phase separation and coarsening phenomenon in Tin/Lead Solders. This model is based on continuum... 

From the past, the damask rose has an important place in various pharmaceutical, food, health and cosmetic industries. This product has the largest cultivated area in Iran, which is about 24,000 hectares, equal to 60% of its total cultivation in the world. Considering the conditions required for the cultivation of this plant, including the low water requirement, the expansion of its cultivation has been considered. One of the important obstacles to not expanding cultivation is manual harvesting, which strongly affects the quality and mass of essential oil and rose water. The efforts that have been made so far in the field of designing and producing the rose harvesting machine have not had... 

In the past decade, with the expansion of e-commerce, there has been an unprecedented growth in demand for online retailing. Due to this growth, fast, efficient, and flawless delivery of shipments to final customers has become especially important. On the other hand, the expansion of urbanization and the increase in urban traffic have also created obstacles to efficient delivery. These factors have introduced new challenges for logistics service provider companies. Several innovations have been proposed in recent years to address these problems. Delivery of goods to locations such as the trunk-in-car or shared delivery locations like lockers is one of the key innovations in solving logistics... 

Study on fish oil Supercritical Fluid Fractionation (SFF) is still an open issue with the objective of large scale production. A fundamental issue for scaling up the process is the knowledge of phase behaviour of the mixtures involved in SFF. So, development of reliable models to describe phase behaviour of the mixtures is crucial. Some thermodynamic models have been suggested which is able to predict solubility of fatty acid ethyl esters in supercritical phase. Some relevant experimental data is necessary to fit and validate the models. In this work, the experiments are designed to collect equilibrium data in the FeyeCon pilot plant. A validated model becomes a fundamental tool for the... 

In the first part of this work, citric acid monomer was selected to produce dendrimer through the divergent method using logical conditions (for controlling its functional groups) on the base of poly (ethylene glycol) as the core. Triblock copolymers (ABA-type) of citric acid and poly (ethylene glycol) (PCA-PEG-PCA) as biocompatible compounds were synthesized in four different molecular weights and applied as nanocarriers. The structure definition of the molecules and nanoparticles were carried out using different spectroscopy methods. Diameter of the synthesized copolymers was investigated using dynamic light scattering (DLS) experiments and transmission electron microscopy (TEM) and it was... 

In a GAN, the generator receives random noise data and produces outputs similar to real data. The generated output data, along with the original dataset, is fed to the discriminator, which distinguishes between real and fake data. The two networks have opposing objectives, but they help each other learn in practice, continuously improving each other's performance. Each of the two networks aims to minimize its own error while maximizing the other's error. John Nash mathematically proved that the optimal solution to these problems occurs when neither agent can further increase its utility. This situation is referred to as Nash equilibrium. If the training data is limited, the GAN cannot... 

Creating sustainable development in today's society is essential, and one of the most important elements to achieve this is the phenomenon of recycling. Lead-acid batteries are one of the sources of environmental pollution, and their separators contain 50% recyclable silica nanoparticles. In this research, impurities in these separators were removed using two methods: washing with water and sandblasting. The purity of recycled nanoparticles was 85.5% in the first method and 98% in the second method. In addition to the importance of recycling, finding a suitable use for recycled materials is also critical. FDM 3D printing is a new method of producing parts, but polypropylene is not commonly...